Re: What c.l.py's opinions about Soft Exception?

[Steven D'Aprano]

On Sat, 08 Mar 2008 22:24:36 -0800, Kay Schluehr wrote:

> On 9 Mrz., 06:30, Steven D'Aprano <[EMAIL PROTECTED]
> cybersource.com.au> wrote:
> 
>> Hard Exceptions: terminate the program unless explicitly silenced Soft
>> Exceptions: pass silently unless explicitly caught
>>
>> In this case, I agree with the Zen of Python ("import this"):
>>
>> Errors should never pass silently.
>> Unless explicitly silenced.
> 
> Exceptions in Python don't necessarily signal errors. Just think about
> StopIteration.

I know that. That's why I said that exceptions were used for signaling 
exceptional events.


> Note also that the common practice of letting *possible* errors passed
> silently is to return None instead of raising an exception. 

"Common"? Who does that?

I know re.search() etc. return None in the event the regex doesn't match. 
That's not an error.



> Moreove people create boilerplate like this
> 
> try:
>k = lst.index(elem)
>...
> except IndexError:
>pass
> 
> instead of
> 
> with lst.index(elem) as k:
> ...

Possibly because the with keyword is quite new and many people don't know 
it, and much code was written before it even existed, or they have to 
support Python 2.4 or older.


> It would be interesting to think about SoftException semantics for such
> clauses: lst.index would neither raises a HardException nor does it
> return None but leads to skipping the with-block.
> 
> Is it really so exotic that it requires the demand for more use cases?


Are the existing solutions really so incomplete that we need yet another 
solution?

What problem are you trying to solve with SoftExceptions?

How would changing lst.index() to raise a soft exception help here?

pos = lst.index('foo')
lst[pos] = 'bar'

What is that code going to do if 'foo' isn't found in lst and it raises a 
silent, unhandled SoftException? Do you expect Python to be context 
sensitive, and raise HardExceptions in some places and SoftExceptions in 
others? Who controls that?



-- 
Steven
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Re: What c.l.py's opinions about Soft Exception?

[Lie]

On Mar 9, 12:05 pm, Kay Schluehr <[EMAIL PROTECTED]> wrote:
> On 9 Mrz., 04:51, Lie <[EMAIL PROTECTED]> wrote:
>
> > A more through implementation would start from the raiser inspecting
> > the execution stack and finding whether there are any try block above
> > it, if no try block exist it pass silently and if one exist it will
> > check whether it have a matching except clause. This also circumvents
> > a problem that simple implementation have, as described below.
>
> This will not be easy in particular in the presence of inheritance and
> dynamism. There is no way to statically decide whether an exception
> BException has the type AException and will be caught by the except
> clause in
>
> try:
> BLOCK
> except AException, e:
> print "SoftException %s caught"%e



> A feasible solution was to invert the try...except statement and
> creating a continuation.
>
> catch AException, a:
>print "SoftException A: %s"%a
> catch BException , b:
>print "SoftException B: %s"%b
> ...
> in:
>BLOCK
>
> Here each SoftException is raised initially when a catch clause is
> entered and a continuation is created that returns to the catch block
> of the raised SoftException if required. When a SoftException is
> raised within BLOCK a lookup will be made and if a corresponding
> SoftException was found that was raised by a catch-clause the current
> control flow will be suspended and the continuation is called.

I'd rather want to avoid any syntax changes, as I wished that Soft
Exception can be added to the language silently[1] so that new
programmers doesn't _need_ to know about it (although knowing it could
change the way they write codes to be more structured and simple).

[1] Definition of silently: Codes that aren't aware of this
functionality shouldn't break. Adding new syntax usually means adding
keywords, making possible break in current program.

On Mar 9, 12:30 pm, Steven D'Aprano <[EMAIL PROTECTED]
cybersource.com.au> wrote:
> On Sat, 08 Mar 2008 19:51:24 -0800, Lie wrote:
> > Soft Exception
> > What is "Soft Exception"?
> > Soft Exception is an exception that if is unhandled, pass silently as if
> > nothing happened. For example, if a variable turns into NoneType, it'll
> > raise Soft Exception that it have become NoneException, programmers that
> > wants to handle it can handle it with a try...except block while
> > programmers that doesn't care about it (or know it won't be a problem to
> > his code) can just leave the code as it is.
>
> > Soft Exception differs from Hard Exceptions (the regular Exception) in a
> > way that Hard Exception must be handled at all cost or the program will
> > be terminated while Soft Exception allow programmers not to handle it if
> > they don't want to.
>
> I don't think that there are very many cases where exceptions can be
> ignored safely. There are two main reasons for using exceptions:
>
> (1) Signaling an exceptional event.

In that case, programmers might decide whether to raise Soft or Hard
Exception. Hard Exception is much preferred.

> (2) An error occurred.

Which must always be handled with Hard Exception.

Adding another thing
(3) Informing codes above it about what's currently happening inside,
the thing is just a mundane report that might be useful to codes above

Which might be a useful place to use SoftExceptions

> I can't think of many cases where you would wish to ignore either, and
> just continue processing. The only examples I can think of are in loops,
> where you are doing the same thing over and over again with just a little
> change, and you wish to skip any problematic data, e.g.:
>
> def plot_graph(func, domain):
>     for x in domain:
>         plot(x, func(x))
>
> If an error occurs in plot() for one particular x value, you would want
> to ignore it and go on to the next point. But that's easy enough to do
> with a regular try...except block.

No, you're misunderstanding the purpose of Soft Exception, it's not
for silencing errors and not so much for exceptional cases. It's for
the more mundane tasks such as:

from __future__ import division

class SomeNumeric(object):
def __div__(a, b):
if b == 0: raise ZeroDivisionError  ## Hard Exception, don't
ignore me!
if a == 0: raise ZeroNumerator  ## Soft Exception
f = a / b
i = a // b
if f == float(i):
raise IntegerDivision  ## Soft Exception
return a // b
else:
raise FloatDivision## Soft Exception
return a / b

Most people can ignore the ZeroNumerator, IntegerDivision, and
FloatDivision exceptions (warnings) because they're excessive and
unnecessary, but some people might want to catch them and do something
else (especially ZeroNumerator). Practicle example, far below.

The example is actually quite bad at demonstrating the purpose of Soft
Exception as it is very simple while Soft Exception is generally more
useful in complex operations. But I want to avoid giving complex
examp

Trac - Does it make sense to keep http://trac.edgewall.org/ticket/4315 open?

[Ilias Lazaridis]

Response to message [1] on trac.devel (as I cannot write there, due to
an informally applied censorship)

Mr. Boos: "I left that ticket open simply to avoid having someone to
reopen it over
and over..."

(note to reader: this someone is me)

Mr. Boos, the ticket status should reflect reality. So, if reality
says "the ticket is open", no one can (should" close it.

The essens of the ticket is, that you should trust you own results.
You should use your development version, in order to obtain feedback.
Of course I understand (seeing the terrible processes of the team),
that you distrust your own results, prefering to let user do the dirty
work of development-version-usage.

Your inability to follow even the most rational suggestions subjecting
development-processes, e.g. this one:

http://trac.edgewall.org/ticket/6614#comment:36

will lead (together with the terrible quality of the trac source-code
base) soon to an even more stucked development progress. Be assured
that users see this (although they don't say much, like me).

Do you actually realize that you're working since over a year on
0.11?

Nothing is more fun that to watch the trac project running into one
after another problem during development. At least you give other
teams a good example of "how to ruine a good open-source product".

http://case.lazaridis.com/wiki/TracAudit

-

To readers:

The project hunts since months a memory-leak - without success.

I'm wondering that python makes so much trouble in finding it. Seems
to be another very fundamental reason to leave this "joke of a
language" (python).

-

[1]

http://groups.google.com/group/trac-dev/msg/1cbcaf2b5fdc8abe

From: Christian Boos <[EMAIL PROTECTED]>
Jeroen Ruigrok van der Werven wrote:

> Does it make sense to keep http://trac.edgewall.org/ticket/4315 open?

I left that ticket open simply to avoid having someone to reopen it
over
and over... That ticket is a bit useless in that it has anyway always
been the policy of the project to run the latest stable release. And
that works quite well in practice. I imagine t.e.o would already be
running 0.11b1 now, if we didn't have those memory issues. As for
documenting the blocker issues, doing that directly on the milestone
page is more effective anyway. So I'd say let's just not make a fuss
about this one and we'll close it once t.e.o gets upgraded to 0.11.

-- Christian
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Re: Regarding coding style

[Lie]

On Mar 9, 3:27 am, [EMAIL PROTECTED] wrote:
> To Lie:
>
> > Personally I preferred a code that has chosen good names but have
> > little or no comments compared to codes that makes bad names and have
>
> Personally I don't.  Show me a good one.  Until you do, it's not that
> I won't like it, it's that I can't.  You know, in linguistics, there's
> what's called 'code switching', which is switching between two
> languages you know midstream.  People can understand 'hear' a language
> but not speak it.  If you speak it, .  If comments aren't
> the 'short version', then patience is the problem.  There's not one
> word for lots and lots of things.  Examples on backorder.

But I much prefer it that the code has good names AND concise
comments, not too short and not too long that it becomes obscure. If
the code is complex, that it's hard to explain in a few sentences, it
might be a good idea to refactor it.

If I have to choose between bad names + twenty pages of documentation
and good names + a paragraph of short documentation, I chose the
latter.

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Re: What c.l.py's opinions about Soft Exception?

[Kay Schluehr]

On 9 Mrz., 09:30, Lie <[EMAIL PROTECTED]> wrote:
> On Mar 9, 12:05 pm, Kay Schluehr <[EMAIL PROTECTED]> wrote:
>
> > On 9 Mrz., 04:51, Lie <[EMAIL PROTECTED]> wrote:
>
> > > A more through implementation would start from the raiser inspecting
> > > the execution stack and finding whether there are any try block above
> > > it, if no try block exist it pass silently and if one exist it will
> > > check whether it have a matching except clause. This also circumvents
> > > a problem that simple implementation have, as described below.
>
> > This will not be easy in particular in the presence of inheritance and
> > dynamism. There is no way to statically decide whether an exception
> > BException has the type AException and will be caught by the except
> > clause in
>
> > try:
> > BLOCK
> > except AException, e:
> > print "SoftException %s caught"%e
> > A feasible solution was to invert the try...except statement and
> > creating a continuation.
>
> > catch AException, a:
> >print "SoftException A: %s"%a
> > catch BException , b:
> >print "SoftException B: %s"%b
> > ...
> > in:
> >BLOCK
>
> > Here each SoftException is raised initially when a catch clause is
> > entered and a continuation is created that returns to the catch block
> > of the raised SoftException if required. When a SoftException is
> > raised within BLOCK a lookup will be made and if a corresponding
> > SoftException was found that was raised by a catch-clause the current
> > control flow will be suspended and the continuation is called.
>
> I'd rather want to avoid any syntax changes, as I wished that Soft
> Exception can be added to the language silently[1] so that new
> programmers doesn't _need_ to know about it (although knowing it could
> change the way they write codes to be more structured and simple).

I just tried to save your proposal from being unimplementable. Maybe
you can comment on it?

I know of course that syntax is Pythons holy cow but I'm not Guidos
mouthpiece and have a different perspective on some aspects of the
system for obvious reasons [1]. I appreciate when people in the Python
community talk about what is useful for them and not what the
imaginary Pythonista superego thinks about them and how it will be
standardized in the end - if anyhow.

I'd like to know if SoftExceptions would make programs more reliable
in the end because people won't use them sparingly but for all kinds
of events that are somewhat "irregular" ( i.e. warnings ) not just for
obvious errors. It's an interesting idea to have an advanced warning
system that is more responsive than just this kind of logging which is
currently implemented. And I'd surely discriminate them from the
current exception handling at least in the design phase. Later
language changes could still be "dissolved".

[1] http://www.fiber-space.de/EasyExtend/doc/EE.html

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gc question

[vpalexander]

I keep seeing destructor calls in wx for ad hoc dialogs and wonder if
this is required, and if so, why would normal gc flow not be good?

  def GetDir(self,Caption,DefaultDir):
dlg = wx.DirDialog(None,Caption,style = 1,defaultPath =
DefaultDir,pos = (10,10))
res = dlg.ShowModal()
pck = dialog.GetPath()
dlg.Destroy()

if res == wx.ID_OK:
  return pck
else:
  return ''


I'd like to write it as:

  def GetDir(self,Caption,DefaultDir):
dlg = wx.DirDialog(None,Caption,style = 1,defaultPath =
DefaultDir,pos = (10,10))

if dlg.ShowModal() == wx.ID_OK:
  return dialog.GetPath()
else:
  return '' # probably implied; del 2 more lines?

...and gc takes care of things once scope is exited? Or is wx more
tricksome than that?
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Re: gc question

[Vince]

On Mar 9, 1:51 am, Marc 'BlackJack' Rintsch <[EMAIL PROTECTED]> wrote:
> On Sun, 09 Mar 2008 01:42:01 -0800, vpalexander wrote:
> > I keep seeing destructor calls in wx for ad hoc dialogs and wonder if
> > this is required, and if so, why would normal gc flow not be good?
>
> Because there is no guarantee when `__del__()` is called or if it is
> called *at all*.
>
> Ciao,
> Marc 'BlackJack' Rintsch

Well, that suits me. The most unnatural thing about Python was
adapting to the idea of just letting unreleased resources go jogging
off wherever. :)

"Where's the f.close?"
"You don't need it!"

Hmmm!
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Re: gc question

[Marc 'BlackJack' Rintsch]

On Sun, 09 Mar 2008 01:42:01 -0800, vpalexander wrote:

> I keep seeing destructor calls in wx for ad hoc dialogs and wonder if
> this is required, and if so, why would normal gc flow not be good?

Because there is no guarantee when `__del__()` is called or if it is
called *at all*.

Ciao,
Marc 'BlackJack' Rintsch
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Re: Arbitrary precision integer arithmetic: ceiling?

[Alasdair]

Thanks, all - you've been most helpful.  By the way, what does // do?  I
haven't yet run down its definition in the manual.

-A.
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Re: Help xxx.py Program Recognition problem

[Vince]

On Mar 8, 9:48 am, [EMAIL PROTECTED] wrote:
> Hi...
>
> I was using Python 2.4 and installed 2.5...I copied all my .py files
> from the Python24\ root directory to the Python25\ root
> directory...when I try to run them by double clicking I get:
> "X.py is not a valid Win32 application"...
>
> Also, the files do not appear to be associated with python...?
>
> I can run them from IDLE...but that is it...
>
> How do I fix this...?
>
> Thanks..
>
> Dave

It sounds like you just want the dbl-click Explorer association ...
that it should establish by default ... you can use Explorer -> Tools -
> Folder Options -> File Types to indicate that you want Idle to
launch .py files.

Also, probably a silly question, but did you verify the download was
the right Win OS version?
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Re: What c.l.py's opinions about Soft Exception?

[Mel]

Lie wrote:
[ ... ]
> Soft Exception
> What is "Soft Exception"?
> Soft Exception is an exception that if is unhandled, pass silently as
> if nothing happened. For example, if a variable turns into NoneType,
> it'll raise Soft Exception that it have become NoneException,
> programmers that wants to handle it can handle it with a try...except
> block while programmers that doesn't care about it (or know it won't
> be a problem to his code) can just leave the code as it is.
> 
> Soft Exception differs from Hard Exceptions (the regular Exception) in
> a way that Hard Exception must be handled at all cost or the program
> will be terminated while Soft Exception allow programmers not to
> handle it if they don't want to.
[ ... ]
> Ideology Base:
> - EAAP: Easier to apologize than to ask permission.

Sort of like a COME FROM statement.  Drastic effects on program 
execution: a `raise SoftException` in the middle of a loop would break 
the loop if a catcher existed, or leave the loop running if not.  It 
would really need the ability to resume after catching an exception. 
You can't really talk about 'apologize' around something that's so 
irreparable.

I'd try for this effect by creating a class of objects with 
well-defined callbacks.

Mel.
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Re: Green's Function

[ericofam]

On Mar 8, 9:46 pm, "Terry Reedy" <[EMAIL PROTECTED]> wrote:
> "olusina eric" <[EMAIL PROTECTED]> wrote in message
>
> news:[EMAIL PROTECTED]
> |  I am new to Python and trying to solve the Hamiltonian of a linear chair
> of atoms using green's function.
> |  Does anyone know any pre-existing library functions and literature that
> could be helpful?
>
> Did you try searching for "Python Green's function"?


I did try serching for Python "Green's function" and useful hit. Also
searched on scipy with no reasonable result too.
EOF
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Re: What c.l.py's opinions about Soft Exception?

[Bryan Olson]

Lie wrote:
[...]
> Soft Exception is an exception that if is unhandled, pass silently as
> if nothing happened.
[...]

> Implementation:
> Simple implementation might be done by catching all exceptions at the
> highest level, then filtering which exceptions would be stopped (Soft
> Exception) and which exceptions will be reraised and terminate the
> program (Hard Exception). This is simple and can be easily implemented
> but is inefficient as that means all soft exceptions must bubble
> through its way to the top to find out if it is Soft or Hard.

If I'm following what you want, that "simple implementation" does
not work.  If a function, possibly deep in a call stack, raises a
soft exception that no caller above catches, what executes next?

Correct me if I'm misunderstanding your idea: You want raising
an un-caught soft exception to be equivalent to a 'pass';
execution continues as if the 'raise' never happened.

Catching everything at a high level does nothing like that. The
exception causes execution to leave the function invoking the
raise statement, and abolishes the stack state from the point of
the raise to the point of the catch.

As Python exceptions currently work, "catching all exceptions
at the highest level" is either what Python already does, or
ill-defined nonsense. When an exception is uncaught, there is
no useful "highest level", other than the level at which the
program simply fails. Python *must* terminate execution upon
an unhanded exception, because the program defined no state
from which executions could correctly continue.

> A more through implementation would start from the raiser inspecting
> the execution stack and finding whether there are any try block above
> it, if no try block exist it pass silently and if one exist it will
> check whether it have a matching except clause. This also circumvents
> a problem that simple implementation have, as described below.

The described problems do not include the "where should execution
resume" problem, which I think is central to the issue. Correct me
if I've misunderstood: A "soft" exception is one that gets raised
only if some calling frame has arranged to catch it.

The if-exception-would-be-unhanded-then-pass logic strikes me as
interesting. It would be a huge change to Python, so I doubt it
will get traction here.  Still, I'd say it's worth more
consideration and discussion.


-- 
--Bryan
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The intel processor reach the very high place...

[sadreti]

The intel processor reach the very high place...

http://intelsprocessor.googlepages.com
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Re: Arbitrary precision integer arithmetic: ceiling?

[Steven D'Aprano]

On Sun, 09 Mar 2008 20:57:15 +1100, Alasdair wrote:

> Thanks, all - you've been most helpful.  By the way, what does // do?  I
> haven't yet run down its definition in the manual.

// is integer division.

>>> 10//5
2
>>> 11//5
2



In Python 2.5 and older, / means integer division, unless you do

from __future__ import division

in which case / is true division, that is:

>>> 10/5
2
>>> 11/5
2.5


In Python 3.x, / will always be true division, and you won't need the 
import.


-- 
Steven
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Re: Checking if a variable is a dictionary

[Guillermo]

>A protocol is just an interface that an object agrees to implement. In
>your case, you would state that every object stored in your special
>dict must implement the to_tagged_value method with certain agreeable
>semantics.

Hm... I've searched about the implementation of protocols and now (I
believe) I know how to implement the iterable protocol, for instance,
but have no clue about how to define my own... I'm surely not thinking
the right way, but I don't seem to be able to wrap my head around the
implementation details of "custom" protocols... Is it just a matter of
extending the different object classes (dict, list, tuple...)? Where
do you put the interface/protocol code? :-?

Regards,

Guillermo
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Re: parralel downloads

[John Deas]

On Mar 8, 5:47 pm, Gary Herron <[EMAIL PROTECTED]> wrote:
> poof65 wrote:
> > For your problem you have to use threads.
>
> Not at all true.  Thread provide one way to solve this, but another is
> the select function.  For this simple case, select() may (or may not) be
> easier to write.  Pseudo-code would look something like this:
>
>   openSockets = list of sockets one per download file:
>   while openSockets:
> readySockets = select(openSockets ...) # Identifies sockets with
> data to be read
> for each s in readSockets:
>   read from s and do whatever with the data
>   if s is at EOF: close and remove s from openSockets
>
> That's it.  Far easier than threads.
>
> Gary Herron
>
> > You can have more information here.
> >http://artfulcode.nfshost.com/files/multi-threading-in-python.html
>
> > On Sat, Mar 8, 2008 at 1:11 PM, John Deas <[EMAIL PROTECTED]> wrote:
>
> >> Hi,
>
> >>  I would like to write a python script that will download a list of
> >>  files (mainly mp3s) from Internet. For this, I thought to use urllib,
> >>  with
>
> >>  urlopen("myUrl").read() and then writing the resulting string to a
> >>  file
>
> >>  my problem is that I would like to download several files at the time.
> >>  As I have not much experience in programming, could you point me the
> >>  easier ways to do this in python ?
>
> >>  Thanks,
>
> >>  JD
> >>  --
> >>  http://mail.python.org/mailman/listinfo/python-list

Thank you both for your help. Threads are working for me. However, a
new problem for me is that the url I want to download are in an xml
file (I want to download podcasts), and is not the same as the file
downloaded:

http://www.sciam.com/podcast/podcast.mp3?e_id=86102326-0B1F-A3D4-74B2BBD61E9ECD2C&ref=p_rss

will be redirected to download:

http://podcast.sciam.com/daily/sa_d_podcast_080307.mp3

is there a way, knowing the first url to get the second at runtime in
my script ?
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Re: What c.l.py's opinions about Soft Exception?

[Lie]

On Mar 9, 6:57 pm, Bryan Olson <[EMAIL PROTECTED]> wrote:
> Lie wrote:
>
> [...]> Soft Exception is an exception that if is unhandled, pass silently as
> > if nothing happened.
>
> [...]
>
> > Implementation:
> > Simple implementation might be done by catching all exceptions at the
> > highest level, then filtering which exceptions would be stopped (Soft
> > Exception) and which exceptions will be reraised and terminate the
> > program (Hard Exception). This is simple and can be easily implemented
> > but is inefficient as that means all soft exceptions must bubble
> > through its way to the top to find out if it is Soft or Hard.
>
> If I'm following what you want, that "simple implementation" does
> not work.  If a function, possibly deep in a call stack, raises a
> soft exception that no caller above catches, what executes next?

The highest possible code that could catch exceptions would have
something like this:

try:
## Everything is happening inside me
except SoftException:
pass

> Correct me if I'm misunderstanding your idea: You want raising
> an un-caught soft exception to be equivalent to a 'pass';
> execution continues as if the 'raise' never happened.
>
> Catching everything at a high level does nothing like that. The
> exception causes execution to leave the function invoking the
> raise statement, and abolishes the stack state from the point of
> the raise to the point of the catch.

The high-level mentioned here is outside our own code, it'll be inside
Python's internal. When CPython (or any implementation of Python) sees
that a particular exception is raised to a certain point, it'll check
whether it is of type SoftException, and if it is, it'll return
program state to the place where the exception is raised before. I
don't know how Python's exception system works (as I tell you I know
next to nothing about Python's internal, although I'm interested to
know), so probably if there is any defect in the implementation
schemes I mentioned, it is simply caused by my ignorance.

> As Python exceptions currently work, "catching all exceptions
> at the highest level" is either what Python already does, or
> ill-defined nonsense. When an exception is uncaught, there is
> no useful "highest level", other than the level at which the
> program simply fails. Python *must* terminate execution upon
> an unhanded exception, because the program defined no state
> from which executions could correctly continue.

That's where the difference between Soft Exceptions and Hard
Exceptions lies. Soft Exception must be continued while Hard
exceptions must terminate programs. Possibly this is impossible at the
absolutely highest level, perhaps it should be done at the level that
can guarantee

> > A more through implementation would start from the raiser inspecting
> > the execution stack and finding whether there are any try block above
> > it, if no try block exist it pass silently and if one exist it will
> > check whether it have a matching except clause. This also circumvents
> > a problem that simple implementation have, as described below.
>
> The described problems do not include the "where should execution
> resume" problem, which I think is central to the issue.

I didn't mentioned it?
I think it's obvious when I say: Execution should resume as if nothing
happened, as if there is nothing raised, that means execution resumes
at the point after the raise statement. If something was caught,
execution isn't resumed and execution continues at the level of the
handler (possibly we could also add a "resume" to explicitly resume
the statement that was caught)

> Correct me
> if I've misunderstood: A "soft" exception is one that gets raised
> only if some calling frame has arranged to catch it.

That could be a way to implement it. And btw, that's a one-line-
explanation that hits the right note (although from a different view I
initially mentioned).

> The if-exception-would-be-unhanded-then-pass logic strikes me as
> interesting. It would be a huge change to Python, so I doubt it
> will get traction here.  Still, I'd say it's worth more
> consideration and discussion.
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Re: What c.l.py's opinions about Soft Exception?

[Lie]

On Mar 9, 4:31 pm, Kay Schluehr <[EMAIL PROTECTED]> wrote:
> On 9 Mrz., 09:30, Lie <[EMAIL PROTECTED]> wrote:
> > On Mar 9, 12:05 pm, Kay Schluehr <[EMAIL PROTECTED]> wrote:
>
> > > On 9 Mrz., 04:51, Lie <[EMAIL PROTECTED]> wrote:
>
> > > > A more through implementation would start from the raiser inspecting
> > > > the execution stack and finding whether there are any try block above
> > > > it, if no try block exist it pass silently and if one exist it will
> > > > check whether it have a matching except clause. This also circumvents
> > > > a problem that simple implementation have, as described below.
>
> > > This will not be easy in particular in the presence of inheritance and
> > > dynamism. There is no way to statically decide whether an exception
> > > BException has the type AException and will be caught by the except
> > > clause in
>
> > > try:
> > >     BLOCK
> > > except AException, e:
> > >     print "SoftException %s caught"%e
> > > A feasible solution was to invert the try...except statement and
> > > creating a continuation.
>
> > > catch AException, a:
> > >    print "SoftException A: %s"%a
> > > catch BException , b:
> > >    print "SoftException B: %s"%b
> > > ...
> > > in:
> > >    BLOCK
>
> > > Here each SoftException is raised initially when a catch clause is
> > > entered and a continuation is created that returns to the catch block
> > > of the raised SoftException if required. When a SoftException is
> > > raised within BLOCK a lookup will be made and if a corresponding
> > > SoftException was found that was raised by a catch-clause the current
> > > control flow will be suspended and the continuation is called.
>
> > I'd rather want to avoid any syntax changes, as I wished that Soft
> > Exception can be added to the language silently[1] so that new
> > programmers doesn't _need_ to know about it (although knowing it could
> > change the way they write codes to be more structured and simple).
>
> I just tried to save your proposal from being unimplementable. Maybe
> you can comment on it?

Perhaps I'm not the appropriate person to talk about whether unchanged
syntax is feasible for such implementation since I basically have no
idea about how Python's internals works. It's only that I think if
current syntax could be used, we could just use it (except if there is
a strong reason why it shouldn't be done).

> I know of course that syntax is Pythons holy cow but I'm not Guidos
> mouthpiece and have a different perspective on some aspects of the
> system for obvious reasons [1].

I agree, everybody have different perspective. But that differences is
what makes languages evolves as it'd be continuously searching for the
most optimal perspective.
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Re: What c.l.py's opinions about Soft Exception?

[Steven D'Aprano]

On Sun, 09 Mar 2008 00:30:51 -0800, Lie wrote:

> (3) Informing codes above it about what's currently happening inside,
> the thing is just a mundane report that might be useful to codes above
> 
> Which might be a useful place to use SoftExceptions

Okay, now we're getting somewhere.

So, I have a function foo() which raises a HardException on error, but it 
also raises a SoftException if it wants to notify me of something 
"mundane".

def foo(sequence):
if args == []:
raise SoftException("empty list")
return len(args)

Now, how do I use that?

try:
   x = foo(something)
except TypeError:
   print "you should pass a sequence"
   sys.exit()  # unrecoverable error
except SoftException:
   print "you passed an empty list"
print x

Am I close?

But there's a problem. Once the SoftException is caught, execution will 
continue from the line "print x" -- but the function foo() never got a 
chance to actually return a result!

In order to make that work, you would need a significant change to 
Python's internals. I don't know how difficult that would be, but I'm 
guess that it would be a lot of work for not much benefit.

But even if that happened, it would mean that the one mechanism has TWO 
different effects:

try:
x = foo(sequence)
except SoftException:
print x  # this is okay, because foo() did return
except TypeError:
print x  # this is NOT okay, because foo() never returned


That is a recipe for confusion.



[...]
> No, you're misunderstanding the purpose of Soft Exception, it's not for
> silencing errors and not so much for exceptional cases. It's for the
> more mundane tasks such as:
[...]
> Perhaps relabeling it as Warning, and renaming raise SoftException as
> give Warning might make it more acceptable? 

Do you realise that Python already has a warnings module?


> And I agree that the
> probability for misuse is quite high, but the benefits is also quite
> high, it's just that you can't see it since you're not used to using
> such exceptions. The benefit of SoftExceptions lies mostly on the
> regular programmings tasks, not the exceptional programming tasks
> 
> Practical Example:
> This example takes _case ideas_ from this simple gravity simulator
> http://www.pygame.org/project/617/ BUT _no line of code is taken from
> it_. I only give this link so you can easily know what the case is about
> without lengthy explanation.
> 
> A particle machine.
> The particle machine calculates gravity created by the particles in a
> field. Additionaly, it clumps together two particles that happens to be
> near enough (less than the sum of their radiuses).
> 
> The force two particle is expressing to each other is calculated with:
> def calculateforce(P1, P2):
> return (P1.mass - P2.mass) / distance(P1, P2)
> 
> and this is done to every particle in the field against the current
> particle.
> 
> And the distance is calculated by:
> def distance(P1, P2)
> return (P1.X - P2.X) ** 2 - (P1.Y - P2.Y) ** 2
> 
> The problem happens when the distance is small enough and we want to
> clump them together.
> 
> A possible solution to this problem might be to check whether distance
> is less than P1.radius + P2.radius in the calculateforce. But, this
> obfuscate the code since we have to separate distance calculation from
> the main formula (see !s), 

I don't agree that this obfuscates the code.


> and this also insist that clumping be done on
> force calculation level (see @s), shortly this piece of code is plain
> bad:
> def distance(P1, P2):
> return (P1.X - P2.X) ** 2 - (P1.Y - P2.Y) ** 2
> 
> def calculateforce(P1, P2):
> ## Separating this dist calculation into its own line is 
> ## necessary if we want to check the value of dist 
> ## Personally I think that's a bit obfuscated. 
> ## Well known formulas should be kept to one line if possible
> !   dist = distance(P1, P2)
> 
> if dist <= P1.radius + P2.radius:
> ## Calling clump() here is bad, because 
> ## there are occasions where we only want to 
> ## calculate force but doesn't want to
> ## clump it
> @   clump(P1, P2)
> else:
> !   return (P1.mass - P2.mass) / dist

I agree that calling clump() there is bad.


 
> ## Codes calling calculateforce()
> # Note: this code is located inside a loop
> 
> F = calculateforce(P1, P2)
> # Do something else, acceleration calculation, movement
> calculations, etc
> 
> 
> A better refactoring would be like this, but this requires calculating
> distance twice (see !s):

That's not better. Don't do it.


> def distance(P1, P2):
> return (P1.X - P2.X) ** 2 - (P1.Y - P2.Y) ** 2
> 
> def calculateforce(P1, P2):
> ## Here distance is calculated once
> !   return (P1.mass - P2.mass) / distance(P1, P2)
> 
> ## Codes calling calculateforce()
> # Note: this code is located inside a loop
> 
> ## Here 

Re: parralel downloads

[John Deas]

On Mar 9, 1:25 pm, John Deas <[EMAIL PROTECTED]> wrote:
> On Mar 8, 5:47 pm, Gary Herron <[EMAIL PROTECTED]> wrote:
>
>
>
> > poof65 wrote:
> > > For your problem you have to use threads.
>
> > Not at all true.  Thread provide one way to solve this, but another is
> > the select function.  For this simple case, select() may (or may not) be
> > easier to write.  Pseudo-code would look something like this:
>
> >   openSockets = list of sockets one per download file:
> >   while openSockets:
> > readySockets = select(openSockets ...) # Identifies sockets with
> > data to be read
> > for each s in readSockets:
> >   read from s and do whatever with the data
> >   if s is at EOF: close and remove s from openSockets
>
> > That's it.  Far easier than threads.
>
> > Gary Herron
>
> > > You can have more information here.
> > >http://artfulcode.nfshost.com/files/multi-threading-in-python.html
>
> > > On Sat, Mar 8, 2008 at 1:11 PM, John Deas <[EMAIL PROTECTED]> wrote:
>
> > >> Hi,
>
> > >>  I would like to write a python script that will download a list of
> > >>  files (mainly mp3s) from Internet. For this, I thought to use urllib,
> > >>  with
>
> > >>  urlopen("myUrl").read() and then writing the resulting string to a
> > >>  file
>
> > >>  my problem is that I would like to download several files at the time.
> > >>  As I have not much experience in programming, could you point me the
> > >>  easier ways to do this in python ?
>
> > >>  Thanks,
>
> > >>  JD
> > >>  --
> > >>  http://mail.python.org/mailman/listinfo/python-list
>
> Thank you both for your help. Threads are working for me. However, a
> new problem for me is that the url I want to download are in an xml
> file (I want to download podcasts), and is not the same as the file
> downloaded:
>
> http://www.sciam.com/podcast/podcast.mp3?e_id=86102326-0B1F-A3D4-74B2...
>
> will be redirected to download:
>
> http://podcast.sciam.com/daily/sa_d_podcast_080307.mp3
>
> is there a way, knowing the first url to get the second at runtime in
> my script ?

Found it: geturl() does the job
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Re: Checking if a variable is a dictionary

[Steven D'Aprano]

On Sun, 09 Mar 2008 05:20:41 -0700, Guillermo wrote:

>>A protocol is just an interface that an object agrees to implement. In
>>your case, you would state that every object stored in your special dict
>>must implement the to_tagged_value method with certain agreeable
>>semantics.
> 
> Hm... I've searched about the implementation of protocols and now (I
> believe) I know how to implement the iterable protocol, for instance,
> but have no clue about how to define my own... I'm surely not thinking
> the right way, but I don't seem to be able to wrap my head around the
> implementation details of "custom" protocols... Is it just a matter of
> extending the different object classes (dict, list, tuple...)? Where do
> you put the interface/protocol code? :-?


A protocol is a convention that you insist other objects must follow, not 
code. To implement that convention, naturally you need to write code, but 
the convention makes the protocol, not the code.

Some examples:

To be considered a writable file, your object must include a write() 
method and a close() method. It doesn't matter what those methods do 
exactly, so long as they behave reasonably. For instance, the close() 
method might do nothing, and the write() method might send an SMS.

To be a random-access writable file, it must also include a seek() method.

To be a sequence, your object must obey the sequence protocol, which says 
it has a __getitem__ method which takes integer arguments starting at 0 
and increasing, until it raises IndexError.

You don't have to write any code to create a protocol, you just have to 
tell people what it is. Here's my parrot protocol:


To be a parrot, your object must have a method speak() which takes an 
integer argument and returns the case-insensitive string "spam" repeated 
that many times.


I'm done. I have a protocol. But if I want to actually use it, then I 
need an object that obeys it, and if I can't wait for somebody else to 
write it, I need to write one myself. So here it is:

class Viking(object):
def __init__(self, case='upper'):
if case == 'upper':
self.case = str.upper
else:
self.case = str.lower
def speak(self, n):
return self.case("spam"*n)


And now Viking instances are also parrots, or rather, they obey the 
parrot protocol:

>>> v = Viking()
>>> v.speak(3)
'SPAMSPAMSPAM'


I hope this helps.


-- 
Steven
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Re: identifying and parsing string in text file

[[EMAIL PROTECTED]]

On 8 mar, 20:49, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
wrote:
> I have a large file that has many lines like this,
>
>  name="DoseReferenceStructureType">SITE
>
> I would like to identify the line by the tag (300a,0014) and then grab
> the name (DoseReferenceStructureType) and value (SITE).

It's obviously an XML file, so use a XML parser - there are SAX and
DOM parsers in the stdlib, as well as the ElementTree module.

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Re: What c.l.py's opinions about Soft Exception?

[Diez B. Roggisch]

Lie schrieb:
> I'm asking about people in c.l.py's opinion about a _probably_ very
> Pythonic way of doing something if such features is implemented. It is
> to be known that I'm not a Python expert and actually relatively new
> to Python programming, so probably I'm just not thinking pythonic
> enough yet or this feature might already exist somewhere in a
> different name.
> Anyway, I'm just asking for opinions, tell me problems I haven't
> foreseen, or whether such things would be hard to implement, or
> whether you think the idea is great or plain bad (and why).
> 
> Soft Exception
> What is "Soft Exception"?
> Soft Exception is an exception that if is unhandled, pass silently as
> if nothing happened. For example, if a variable turns into NoneType,
> it'll raise Soft Exception that it have become NoneException,
> programmers that wants to handle it can handle it with a try...except
> block while programmers that doesn't care about it (or know it won't
> be a problem to his code) can just leave the code as it is.
> 
> Soft Exception differs from Hard Exceptions (the regular Exception) in
> a way that Hard Exception must be handled at all cost or the program
> will be terminated while Soft Exception allow programmers not to
> handle it if they don't want to.



Is this soft-exception implemented anywhere, so that one can see what 
experiences and best practices have evolved around using it?

Diez
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Uninstalling Eggs

[PB]

I just installed the Shove module with the monumentally crap
setuptools. Whilst the install succeeded, imports now trigger errors,
so clearly it did not install correctly. Can I simply delete the .egg
file from my lib/python2.3/site-packages/ directory?

Cheers,
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Re: Checking if a variable is a dictionary

[Guillermo]

Mamma mia! My head just exploded. I've seen the light.

So you only need to ·want· to have a protocol? That's amazing... Far
beyond the claim that Python is easy. You define protocols in writing
basically! Even my grandma could have her own Python protocol.

Okay, so I think I know where's the catch now -- you must rely on the
fact that the protocol is implemented, there's no way to enforce it if
you're expecting a parrot-like object. You'd try to call the speak()
method and deal with the error if there's no such method?

Thanks a lot!

Guillermo
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Re: Checking if a variable is a dictionary

[Steven D'Aprano]

On Sun, 09 Mar 2008 06:58:15 -0700, Guillermo wrote:

> Okay, so I think I know where's the catch now -- you must rely on the
> fact that the protocol is implemented, there's no way to enforce it if
> you're expecting a parrot-like object. You'd try to call the speak()
> method and deal with the error if there's no such method?

That's right. That's called "duck typing" -- if all you want is something 
that quacks like a duck, then it doesn't matter if it actually is a duck 
or not.

Or if you prefer: if it quacks like a duck and swims like a duck, then 
it's close enough to a duck as to make no difference.


Sometimes though, you need to check for a parrot up front. So I'd so this:

try:
something.speak
except AttributeError:
# No speak() method, so it can't be a parrot.
do_something_else()
else:
# It seems to follow the parrot protocol.
yummy_goodness = something.speak(5)
assert "spam" in yummy_goodness.lower()


-- 
Steven
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Re: What c.l.py's opinions about Soft Exception?

[Kay Schluehr]

On 9 Mrz., 13:50, Lie <[EMAIL PROTECTED]> wrote:
> On Mar 9, 4:31 pm, Kay Schluehr <[EMAIL PROTECTED]> wrote:
>
>
>
> > On 9 Mrz., 09:30, Lie <[EMAIL PROTECTED]> wrote:
> > > On Mar 9, 12:05 pm, Kay Schluehr <[EMAIL PROTECTED]> wrote:
>
> > > > On 9 Mrz., 04:51, Lie <[EMAIL PROTECTED]> wrote:
>
> > > > > A more through implementation would start from the raiser inspecting
> > > > > the execution stack and finding whether there are any try block above
> > > > > it, if no try block exist it pass silently and if one exist it will
> > > > > check whether it have a matching except clause. This also circumvents
> > > > > a problem that simple implementation have, as described below.
>
> > > > This will not be easy in particular in the presence of inheritance and
> > > > dynamism. There is no way to statically decide whether an exception
> > > > BException has the type AException and will be caught by the except
> > > > clause in
>
> > > > try:
> > > > BLOCK
> > > > except AException, e:
> > > > print "SoftException %s caught"%e
> > > > A feasible solution was to invert the try...except statement and
> > > > creating a continuation.
>
> > > > catch AException, a:
> > > >print "SoftException A: %s"%a
> > > > catch BException , b:
> > > >print "SoftException B: %s"%b
> > > > ...
> > > > in:
> > > >BLOCK
>
> > > > Here each SoftException is raised initially when a catch clause is
> > > > entered and a continuation is created that returns to the catch block
> > > > of the raised SoftException if required. When a SoftException is
> > > > raised within BLOCK a lookup will be made and if a corresponding
> > > > SoftException was found that was raised by a catch-clause the current
> > > > control flow will be suspended and the continuation is called.
>
> > > I'd rather want to avoid any syntax changes, as I wished that Soft
> > > Exception can be added to the language silently[1] so that new
> > > programmers doesn't _need_ to know about it (although knowing it could
> > > change the way they write codes to be more structured and simple).
>
> > I just tried to save your proposal from being unimplementable. Maybe
> > you can comment on it?
>
> Perhaps I'm not the appropriate person to talk about whether unchanged
> syntax is feasible for such implementation since I basically have no
> idea about how Python's internals works. It's only that I think if
> current syntax could be used, we could just use it (except if there is
> a strong reason why it shouldn't be done).

You are an appropriate person to consider the workflow in a dynamic
language, no matter how the language is implemented internally.

Just start with function calls

   maybe_raise(ZeroDivisionError)

The only requirement is that maybe_raise has to know when it shall
raise ZeroDivisionError. This depends on whether the exception is
caught. How do the program knows this in advance? There are no static
analysis techniques available.

When maybe_raise is entered the system must know that the exception is
handled in the future. You can't inspect the call stack for this
purpose because the call stack represents past events and
continuations ( and you can't rely on names ).

So you need something like this

   do_softexception(ZeroDivisionError)
   try:
  TRY_BLOCK
   except ZeroDivisionError:
  EXCEPT_BLOCK

But this looks odd and the solution isn't DRY. So better one macro-
transforms a new statement into this form.


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Re: Converting a string to the most probable type

[Malcolm Greene]

Pierre,

> That's fine for people who write floats with a "." ; but others learn to 
> enter them with ","

I have also been looking for a similar Python conversion library. One of
my requirements is that such a library must be locale aware (so it can
make reasonable assumptions regarding locale properties like thousands
separators, decimal points, etc) - either via a locale attribute or by
examining the locale of the thread its running under.

Malcolm
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Re: for-else

[egbert]

On Sat, Mar 08, 2008 at 04:15:31PM -0500, Terry Reedy wrote:
> 
> I am sorry if you cannot appreciate such elegance 
> and can only spit on it as 'orwellian'.
> 
I admire the elegance of your examples and your explanation.
I will keep a copy of it in my Beazley,
for I am afraid I have to read it again.
As for orwellian, I must admit 
that I was quite happy when I thought of using that word, 
but that it was not my luckiest thought.

But I have to persist in my malice.

In the following snippet it is not at all clear
to the naive programmer (me) that the else refers to an 
iterator_is_exhausted condition,
whatever logical explanation you may offer.

.  for each_item in item_list:
.do_something()
.  else:
.do_else()

My temporary solution will be to accompany this else
with an appropriate comment: # exhausted

e
-- 
Egbert Bouwman - Keizersgracht 197 II - 1016 DS  Amsterdam - 020 6257991

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unable to install gdal

[luis]

Hi

On Windows xp sp2 and python 2.4

Yesterday I running old versions of gdal, and I try to upgrade

I download gdalwin32exe150.zip and gdal-python-13.win32-py2.4.exe
I unzip gdalwin32exe150.zip in C:\gdalwin32-1.5

I follow install's instructions from 
http://trac.osgeo.org/gdal/wiki/GdalOgrInPython,
all is ok, I set path and path_data variables with correct values, but
whe I run a script, an error raises

from osgeo import ogr
  File "C:\Python24\Lib\site-packages\osgeo\ogr.py", line 7, in ?
import _ogr
ImportError: DLL load failed: process not found



Also I try with instructions from
http://www.urbansim.org/opus/stable-releases/opus-2006-11-21/docs/gdalinstall.html
I move _gdal.pyd (and the others *.pyd) from my Python installation's
(C:\Python24\Lib\site-packages\osgeo) into my Python installation's
DLLs folder (C:\Python24\DLLs).
When I run the script the error message persists.

Some help is welcome.


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Changing the size of a Button

[K Viltersten]

How do i change the size of a Button
(using Tkinter), other than to set it
during construction?

I've found methods for getting the 
size but not applying them.

I've been laborating with .setvar(*)
but i've been unsuccessful.

--
Regards
Konrad Viltersten

sleep- a substitute for coffee for the poor
ambition - lack of sense to be lazy

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Returning values from function to Python shell/IPython

[Karlo Lozovina]

Hi all! 

I have a runTest() function inside my module, which sets up and initializes
lots of objects and performs some basic tests on them. Usually (from
IPython) I just write `run my_module.py`, and then `runTest()`. But
sometimes I would like to manually twiddle with objects runTest creates. Is
there any way I can "return" all those objects local to runTest(), and have
them available in IPython (or ordinary Python shell)?

Thanks...


P.S.
I know I can do it from a:

if __name__ == '__main__':
  # lots of object initialization...

and then have all those objects available in the interpreter.

-- 
Karlo Lozovina -- Mosor
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Re: Returning values from function to Python shell/IPython

[Jorge Vargas]

On Sun, Mar 9, 2008 at 9:56 AM, Karlo Lozovina <[EMAIL PROTECTED]> wrote:
> Hi all!
>
>  I have a runTest() function inside my module, which sets up and initializes
>  lots of objects and performs some basic tests on them. Usually (from
>  IPython) I just write `run my_module.py`, and then `runTest()`. But
>  sometimes I would like to manually twiddle with objects runTest creates. Is
>  there any way I can "return" all those objects local to runTest(), and have
>  them available in IPython (or ordinary Python shell)?

well after all it's a function so the only ways you can get things out
of it are:
- return a dict with all the objects
- use global (very messy)
- use a decorator to do either of the above.


on the other hand have you consider using a proper test package?
instead of inspecting the objects manually from the shell you could
make it all automatic. with assert statements. you could use the std.
python testing modules http://docs.python.org/lib/development.html or
something less verbosed like nose
http://code.google.com/p/python-nose/
>
>  Thanks...
>
>
>  P.S.
>  I know I can do it from a:
>
>  if __name__ == '__main__':
>   # lots of object initialization...
>
>  and then have all those objects available in the interpreter.
>
>  --
>  Karlo Lozovina -- Mosor
>  --
>  http://mail.python.org/mailman/listinfo/python-list
>
-- 
http://mail.python.org/mailman/listinfo/python-list

pure python hyphenator

[Wilbert Berendsen]

Hi all, I'm just new to this list and I'm a musician and hobby programmer. I 
am busy with LilyKDE, a python plugin package for KDE's editor Kate, that 
makes using the LilyPond music typesetter from within Kate easier.

While already busy writing a python module for breaking lyrics text (using 
hyphenation dicts from e.g. OpenOffice.org) I found Dr.Leo's PyHyphen. But 
just for fun I also continued my own plain python module, which now has it's 
SVN repository at: http://python-hyphenator.googlecode.com/ and it's PyPI 
page at: http://pypi.python.org/pypi/hyphenator . It needs more testing but 
seems to work nice.

LilyKDE is located at http://lilykde.googlecode.com/

all the best.
Guido and community: thanks for such a nice programming language,
Wilbert Berendsen

-- 
http://www.wilbertberendsen.nl/
"You must be the change you wish to see in the world."
-- Mahatma Gandi
-- 
http://mail.python.org/mailman/listinfo/python-list

Re: help on file storage for split multi part download

[Gabriel Genellina]

En Sat, 08 Mar 2008 08:27:12 -0200, <[EMAIL PROTECTED]> escribió:
> On Mar 7, 2:14 pm, "Gabriel Genellina" <[EMAIL PROTECTED]> wrote:
>> En Fri, 07 Mar 2008 04:16:42 -0200, <[EMAIL PROTECTED]> escribi�:
>>
>> > BUT the thing thats going in my mind is thread safety. i plan to start
>> > each part of the filedownloadin a different thread. and then when
>> > each thread had downloaded more than 100kb (or eof or boundary
>> > reached) write the buffer to the disk. can this be achieved using
>> > mutex ? i have never shared objects between threads.
>>
>> Use a different (single) thread to write the file; the others put write
>> requests on a Queue.queue object, and the writer just gets the requests
>> and processes them.
>>
>> > is there a way to write this without using threads at all ???
>>
>> Using asyncore, and perhaps the Twisted framework.
>
> asyncore is basically a server thing right?

asyncore is usually used to build servers, because in a server you want to  
handle many requests with few resources, but you can use it to write a  
client too.
Here is an example: http://effbot.org/zone/asyncore-ftp-client.htm

How many files and how many simultaneous connections do you plan to  
handle? Using multiple threads to download and a single thread to write,  
connected thru a queue, looks like the "simplest thing that probably  
works" to me unless you have other constraints.

-- 
Gabriel Genellina

-- 
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Re: Returning values from function to Python shell/IPython

[Karlo Lozovina]

Jorge Vargas wrote:

> well after all it's a function so the only ways you can get things out
> of it are:
> - return a dict with all the objects
> - use global (very messy)
> - use a decorator to do either of the above.

Messy, all of those... :(.

> on the other hand have you consider using a proper test package?
> instead of inspecting the objects manually from the shell you could
> make it all automatic. with assert statements. you could use the std.
> python testing modules http://docs.python.org/lib/development.html or
> something less verbosed like nose

Usually, I'm using standard Python testing modules, but sometimes that is
just an overkill. Sometimes I like to do 'exploratory programming',
especially in the early phases of development - create a bunch of objects I
want to play with and do that from IPython. Only way I found out to
somewhat automate this procedure is to have a function that creates all of
the test objects, and then raises an exception at the end. IPython starts
ipdb, so I can work with the objects the function created (without copying
them back to the shell). But this somehow looks too hack-ish for me, so I
was wondering if there was an alternative...

Anyway, thanks for your answer ;).

-- 
Karlo Lozovina -- Mosor
-- 
http://mail.python.org/mailman/listinfo/python-list

Need Help Building PythonQt on Windows

[Jeff Schiller]

Hello,

I'm creating an application using Qt (4.4 Beta atm).  I have pretty
close to zero experience with Python (consisting of installing the
Python interpreter, downloading a python programming and executing it
on the command-line).

I would like to invoke a Python script from my C++ Qt program and
capture its output as a C++ structure.  It seems that PythonQt might
be suitable for my needs.

Being a Qt program, I want this thing to be cross-platform.  I'm
having trouble getting things set up in Windows.  Has anyone had any
experience with this?

I've built Qt from source using the mingw32 compiler.  I installed
Python 2.5 binary.  I am trying to build PythonQt from source.  As per
http://pythonqt.sourceforge.net/#Building it says I need a "developer
installation" of Python containing the header files and  the library
files.  When I look at my system after installing the Python 2.5
binary, I can see I have header files (C:\Python25\include), a 199k
python25.lib (C:\Python25\libs) and a 2MB python25.dll
(C:\Windows\System32\).  Have I got what I need?

I have tried to set up my symbols (PYTHON_PATH, PYTHON_LIB,
PYTHONQT_ROOT).  I generate the Makefile (using qmake) and it starts
to build but then it fails:

g++ -enable-stdcall-fixup -Wl,-enable-auto-import
-Wl,-enable-runtime-pseudo-reloc -mthreads -Wl -shared
-Wl,--out-implib,lib\libPythonQt.a -o lib\PythonQt.dll
object_script.PythonQt.Debug  -L"c:\Qt\4.4.0-beta1\lib"
"c:\Python25\libs"/python25.lib -lQtGuid4 -lQtCored4
./debug\PythonQt.o: In function `ZN8PythonQtC2Ei':
C:/PythonQt-1.0/src/PythonQt.cpp:118: undefined reference to
`_imp__Py_NoSiteFlag'
./debug\PythonQt.o: In function `ZN8PythonQtC1Ei':
C:/PythonQt-1.0/src/PythonQt.cpp:118: undefined reference to
`_imp__Py_NoSiteFlag'
./debug\PythonQt.o: In function `ZN15PythonQtPrivate11wrapQObjectEP7QObject':
C:/PythonQt-1.0/src/PythonQt.cpp:256: undefined reference to
`_imp___Py_NoneStruct'
C:/PythonQt-1.0/src/PythonQt.cpp:257: undefined reference to
`_imp___Py_NoneStruct'
./debug\PythonQt.o: In function `ZN15PythonQtPrivate7wrapPtrEPvRK10QByteArray':
C:/PythonQt-1.0/src/PythonQt.cpp:281: undefined reference to
`_imp___Py_NoneStruct'
C:/PythonQt-1.0/src/PythonQt.cpp:282: undefined reference to
`_imp___Py_NoneStruct'
./debug\PythonQt.o: In function
`ZN8PythonQt13introspectionEP7_objectRK7QStringNS_10ObjectTypeE':
C:/PythonQt-1.0/src/PythonQt.cpp:620: undefined reference to
`_imp__PyClass_Type'
C:/PythonQt-1.0/src/PythonQt.cpp:625: undefined reference to
`_imp__PyClass_Type'
C:/PythonQt-1.0/src/PythonQt.cpp:625: undefined reference to
`_imp__PyCFunction_Type'
...

Since I'm new to compiling Qt with mingw and completely new to python,
I was hoping for tips on why I'm getting these errors.  If anyone has
a better suggestion for a forum/mailing list then please let me know.

Thanks,
Jeff
-- 
http://mail.python.org/mailman/listinfo/python-list

Re: Returning values from function to Python shell/IPython

[Jorge Vargas]

On Sun, Mar 9, 2008 at 11:07 AM, Karlo Lozovina <[EMAIL PROTECTED]> wrote:
> Jorge Vargas wrote:
>
>  > well after all it's a function so the only ways you can get things out
>  > of it are:
>  > - return a dict with all the objects
>  > - use global (very messy)
>  > - use a decorator to do either of the above.
>
>  Messy, all of those... :(.
>
>
>  > on the other hand have you consider using a proper test package?
>  > instead of inspecting the objects manually from the shell you could
>  > make it all automatic. with assert statements. you could use the std.
>  > python testing modules http://docs.python.org/lib/development.html or
>  > something less verbosed like nose
>
>  Usually, I'm using standard Python testing modules, but sometimes that is
>  just an overkill. Sometimes I like to do 'exploratory programming',
>  especially in the early phases of development - create a bunch of objects I
>  want to play with and do that from IPython. Only way I found out to
>  somewhat automate this procedure is to have a function that creates all of
>  the test objects, and then raises an exception at the end. IPython starts
>  ipdb, so I can work with the objects the function created (without copying
>  them back to the shell). But this somehow looks too hack-ish for me, so I
>  was wondering if there was an alternative...
>
ohhh if that is the case then what you are doing seems to be the
optimal. Just have module lvl code ran the testing in fact I don't
even put those into the if __name__, the reason is that this is just
temp testing that will later become real unit testing, and will never
hit a production app. it gives you the most flexibility.
>  Anyway, thanks for your answer ;).
>
welcome
>
>
>  --
>  Karlo Lozovina -- Mosor
>  --
>  http://mail.python.org/mailman/listinfo/python-list
>
-- 
http://mail.python.org/mailman/listinfo/python-list

Re: Need Help Building PythonQt on Windows

[Diez B. Roggisch]

Jeff Schiller schrieb:
> Hello,
> 
> I'm creating an application using Qt (4.4 Beta atm).  I have pretty
> close to zero experience with Python (consisting of installing the
> Python interpreter, downloading a python programming and executing it
> on the command-line).
> 
> I would like to invoke a Python script from my C++ Qt program and
> capture its output as a C++ structure.  It seems that PythonQt might
> be suitable for my needs.
> 
> Being a Qt program, I want this thing to be cross-platform.  I'm
> having trouble getting things set up in Windows.  Has anyone had any
> experience with this?
> 
> I've built Qt from source using the mingw32 compiler.  I installed
> Python 2.5 binary.  I am trying to build PythonQt from source.  As per
> http://pythonqt.sourceforge.net/#Building it says I need a "developer
> installation" of Python containing the header files and  the library
> files.  When I look at my system after installing the Python 2.5
> binary, I can see I have header files (C:\Python25\include), a 199k
> python25.lib (C:\Python25\libs) and a 2MB python25.dll
> (C:\Windows\System32\).  Have I got what I need?
> 
> I have tried to set up my symbols (PYTHON_PATH, PYTHON_LIB,
> PYTHONQT_ROOT).  I generate the Makefile (using qmake) and it starts
> to build but then it fails:
> 
> g++ -enable-stdcall-fixup -Wl,-enable-auto-import
> -Wl,-enable-runtime-pseudo-reloc -mthreads -Wl -shared
> -Wl,--out-implib,lib\libPythonQt.a -o lib\PythonQt.dll
> object_script.PythonQt.Debug  -L"c:\Qt\4.4.0-beta1\lib"
> "c:\Python25\libs"/python25.lib -lQtGuid4 -lQtCored4
> ./debug\PythonQt.o: In function `ZN8PythonQtC2Ei':
> C:/PythonQt-1.0/src/PythonQt.cpp:118: undefined reference to
> `_imp__Py_NoSiteFlag'
> ./debug\PythonQt.o: In function `ZN8PythonQtC1Ei':
> C:/PythonQt-1.0/src/PythonQt.cpp:118: undefined reference to
> `_imp__Py_NoSiteFlag'
> ./debug\PythonQt.o: In function `ZN15PythonQtPrivate11wrapQObjectEP7QObject':
> C:/PythonQt-1.0/src/PythonQt.cpp:256: undefined reference to
> `_imp___Py_NoneStruct'
> C:/PythonQt-1.0/src/PythonQt.cpp:257: undefined reference to
> `_imp___Py_NoneStruct'
> ./debug\PythonQt.o: In function 
> `ZN15PythonQtPrivate7wrapPtrEPvRK10QByteArray':
> C:/PythonQt-1.0/src/PythonQt.cpp:281: undefined reference to
> `_imp___Py_NoneStruct'
> C:/PythonQt-1.0/src/PythonQt.cpp:282: undefined reference to
> `_imp___Py_NoneStruct'
> ./debug\PythonQt.o: In function
> `ZN8PythonQt13introspectionEP7_objectRK7QStringNS_10ObjectTypeE':
> C:/PythonQt-1.0/src/PythonQt.cpp:620: undefined reference to
> `_imp__PyClass_Type'
> C:/PythonQt-1.0/src/PythonQt.cpp:625: undefined reference to
> `_imp__PyClass_Type'
> C:/PythonQt-1.0/src/PythonQt.cpp:625: undefined reference to
> `_imp__PyCFunction_Type'
> ...
> 
> Since I'm new to compiling Qt with mingw and completely new to python,
> I was hoping for tips on why I'm getting these errors.  If anyone has
> a better suggestion for a forum/mailing list then please let me know.


A few of suggestions:

  - take this to the PyQt mailing list 
(http://www.riverbankcomputing.com/mailman/listinfo/pyqt)

  - you only *need* pyqt if what you want to do in python has really to 
deal with Qt-objects - maybe "simple" embedding is enough for your needs

  - I don't see why you need to compile PyQt yourself at all - are you 
sure you can't use the stock PyQt for windows? What makes you believe 
you really need this to be self-compiled?

Diez
-- 
http://mail.python.org/mailman/listinfo/python-list

Re: Can't get items out of a set?

[Raymond Hettinger]

> > The intern() builtin uses this approach:
>
> >    interned = {}
> >    def intern(s):
> >         if s in interned:
> >             return interned[s]
> >         interned[s] = s
> >         return s
>
> If you've seen it before, and have the old one, return the old one.
> Do I have this straight?

Right.

-- 
http://mail.python.org/mailman/listinfo/python-list

Re: Need Help Building PythonQt on Windows

[Jeff Schiller]

I said "PythonQt" not PyQt.  That's an important distinction, I think :)

See http://pythonqt.sourceforge.net/

Regards,
Jeff

On 3/9/08, Diez B. Roggisch <[EMAIL PROTECTED]> wrote:
> Jeff Schiller schrieb:
>
> > Hello,
>  >
>  > I'm creating an application using Qt (4.4 Beta atm).  I have pretty
>  > close to zero experience with Python (consisting of installing the
>  > Python interpreter, downloading a python programming and executing it
>  > on the command-line).
>  >
>  > I would like to invoke a Python script from my C++ Qt program and
>  > capture its output as a C++ structure.  It seems that PythonQt might
>  > be suitable for my needs.
>  >
>  > Being a Qt program, I want this thing to be cross-platform.  I'm
>  > having trouble getting things set up in Windows.  Has anyone had any
>  > experience with this?
>  >
>  > I've built Qt from source using the mingw32 compiler.  I installed
>  > Python 2.5 binary.  I am trying to build PythonQt from source.  As per
>  > http://pythonqt.sourceforge.net/#Building it says I need a "developer
>  > installation" of Python containing the header files and  the library
>  > files.  When I look at my system after installing the Python 2.5
>  > binary, I can see I have header files (C:\Python25\include), a 199k
>  > python25.lib (C:\Python25\libs) and a 2MB python25.dll
>  > (C:\Windows\System32\).  Have I got what I need?
>  >
>  > I have tried to set up my symbols (PYTHON_PATH, PYTHON_LIB,
>  > PYTHONQT_ROOT).  I generate the Makefile (using qmake) and it starts
>  > to build but then it fails:
>  >
>  > g++ -enable-stdcall-fixup -Wl,-enable-auto-import
>  > -Wl,-enable-runtime-pseudo-reloc -mthreads -Wl -shared
>  > -Wl,--out-implib,lib\libPythonQt.a -o lib\PythonQt.dll
>  > object_script.PythonQt.Debug  -L"c:\Qt\4.4.0-beta1\lib"
>  > "c:\Python25\libs"/python25.lib -lQtGuid4 -lQtCored4
>  > ./debug\PythonQt.o: In function `ZN8PythonQtC2Ei':
>  > C:/PythonQt-1.0/src/PythonQt.cpp:118: undefined reference to
>  > `_imp__Py_NoSiteFlag'
>  > ./debug\PythonQt.o: In function `ZN8PythonQtC1Ei':
>  > C:/PythonQt-1.0/src/PythonQt.cpp:118: undefined reference to
>  > `_imp__Py_NoSiteFlag'
>  > ./debug\PythonQt.o: In function 
> `ZN15PythonQtPrivate11wrapQObjectEP7QObject':
>  > C:/PythonQt-1.0/src/PythonQt.cpp:256: undefined reference to
>  > `_imp___Py_NoneStruct'
>  > C:/PythonQt-1.0/src/PythonQt.cpp:257: undefined reference to
>  > `_imp___Py_NoneStruct'
>  > ./debug\PythonQt.o: In function 
> `ZN15PythonQtPrivate7wrapPtrEPvRK10QByteArray':
>  > C:/PythonQt-1.0/src/PythonQt.cpp:281: undefined reference to
>  > `_imp___Py_NoneStruct'
>  > C:/PythonQt-1.0/src/PythonQt.cpp:282: undefined reference to
>  > `_imp___Py_NoneStruct'
>  > ./debug\PythonQt.o: In function
>  > `ZN8PythonQt13introspectionEP7_objectRK7QStringNS_10ObjectTypeE':
>  > C:/PythonQt-1.0/src/PythonQt.cpp:620: undefined reference to
>  > `_imp__PyClass_Type'
>  > C:/PythonQt-1.0/src/PythonQt.cpp:625: undefined reference to
>  > `_imp__PyClass_Type'
>  > C:/PythonQt-1.0/src/PythonQt.cpp:625: undefined reference to
>  > `_imp__PyCFunction_Type'
>  > ...
>  >
>  > Since I'm new to compiling Qt with mingw and completely new to python,
>  > I was hoping for tips on why I'm getting these errors.  If anyone has
>  > a better suggestion for a forum/mailing list then please let me know.
>
>
>
> A few of suggestions:
>
>   - take this to the PyQt mailing list
>  (http://www.riverbankcomputing.com/mailman/listinfo/pyqt)
>
>   - you only *need* pyqt if what you want to do in python has really to
>  deal with Qt-objects - maybe "simple" embedding is enough for your needs
>
>   - I don't see why you need to compile PyQt yourself at all - are you
>  sure you can't use the stock PyQt for windows? What makes you believe
>  you really need this to be self-compiled?
>
>  Diez
>
> --
>  http://mail.python.org/mailman/listinfo/python-list
>
-- 
http://mail.python.org/mailman/listinfo/python-list

Re: Need Help Building PythonQt on Windows

[Michael Wieher]

2008/3/9, Jeff Schiller <[EMAIL PROTECTED]>:
>
> Hello,




I'm creating an application using Qt (4.4 Beta atm).  I have pretty
> close to zero experience with Python (consisting of installing the
> Python interpreter, downloading a python programming and executing it
> on the command-line).
>
> I would like to invoke a Python script from my C++ Qt program and
> capture its output as a C++ structure.  It seems that PythonQt might
> be suitable for my needs.
>
> Being a Qt program, I want this thing to be cross-platform.  I'm
> having trouble getting things set up in Windows.  Has anyone had any
> experience with this?
>
> I've built Qt from source using the mingw32 compiler.  I installed
> Python 2.5 binary.  I am trying to build PythonQt from source.  As per
> http://pythonqt.sourceforge.net/#Building it says I need a "developer
> installation" of Python containing the header files and  the library
> files.  When I look at my system after installing the Python 2.5
> binary, I can see I have header files (C:\Python25\include), a 199k
> python25.lib (C:\Python25\libs) and a 2MB python25.dll
> (C:\Windows\System32\).  Have I got what I need?
>
> I have tried to set up my symbols (PYTHON_PATH, PYTHON_LIB,
> PYTHONQT_ROOT).  I generate the Makefile (using qmake) and it starts
> to build but then it fails:
>
> g++ -enable-stdcall-fixup -Wl,-enable-auto-import
> -Wl,-enable-runtime-pseudo-reloc -mthreads -Wl -shared
> -Wl,--out-implib,lib\libPythonQt.a -o lib\PythonQt.dll
> object_script.PythonQt.Debug  -L"c:\Qt\4.4.0-beta1\lib"
> "c:\Python25\libs"/python25.lib -lQtGuid4 -lQtCored4
> ./debug\PythonQt.o: In function `ZN8PythonQtC2Ei':
> C:/PythonQt-1.0/src/PythonQt.cpp:118: undefined reference to
> `_imp__Py_NoSiteFlag'
> ./debug\PythonQt.o: In function `ZN8PythonQtC1Ei':
> C:/PythonQt-1.0/src/PythonQt.cpp:118: undefined reference to
> `_imp__Py_NoSiteFlag'
> ./debug\PythonQt.o: In function
> `ZN15PythonQtPrivate11wrapQObjectEP7QObject':
> C:/PythonQt-1.0/src/PythonQt.cpp:256: undefined reference to
> `_imp___Py_NoneStruct'
> C:/PythonQt-1.0/src/PythonQt.cpp:257: undefined reference to
> `_imp___Py_NoneStruct'
> ./debug\PythonQt.o: In function
> `ZN15PythonQtPrivate7wrapPtrEPvRK10QByteArray':
> C:/PythonQt-1.0/src/PythonQt.cpp:281: undefined reference to
> `_imp___Py_NoneStruct'
> C:/PythonQt-1.0/src/PythonQt.cpp:282: undefined reference to
> `_imp___Py_NoneStruct'
> ./debug\PythonQt.o: In function
> `ZN8PythonQt13introspectionEP7_objectRK7QStringNS_10ObjectTypeE':
> C:/PythonQt-1.0/src/PythonQt.cpp:620: undefined reference to
> `_imp__PyClass_Type'
> C:/PythonQt-1.0/src/PythonQt.cpp:625: undefined reference to
> `_imp__PyClass_Type'
> C:/PythonQt-1.0/src/PythonQt.cpp:625: undefined reference to
> `_imp__PyCFunction_Type'
> ...
>
> Since I'm new to compiling Qt with mingw and completely new to python,
> I was hoping for tips on why I'm getting these errors.  If anyone has
> a better suggestion for a forum/mailing list then please let me know.
>
> Thanks,
> Jeff
>
> --
> http://mail.python.org/mailman/listinfo/python-list



Another thing to be aware of, although this might not be something you need
to worry about, is that there are debug-versions of the python libraries
that are not installed by the MSI installer on windows.  Sadly, the only way
to get these libraries is to compile Python from source on your Windows
machine, being sure to also create the debug libraries at this time.  I
don't know if you need them or not, because the error message you got was
not entirely descriptive.

~mike
-- 
http://mail.python.org/mailman/listinfo/python-list

Re: What c.l.py's opinions about Soft Exception?

[Lie]

On Mar 9, 7:54 pm, Steven D'Aprano <[EMAIL PROTECTED]
cybersource.com.au> wrote:
> On Sun, 09 Mar 2008 00:30:51 -0800, Lie wrote:
> > (3) Informing codes above it about what's currently happening inside,
> > the thing is just a mundane report that might be useful to codes above
>
> > Which might be a useful place to use SoftExceptions
>
> Okay, now we're getting somewhere.
>
> So, I have a function foo() which raises a HardException on error, but it
> also raises a SoftException if it wants to notify me of something
> "mundane".
>
> def foo(sequence):
>     if args == []:
>         raise SoftException("empty list")
>     return len(args)
>
> Now, how do I use that?
>
> try:
>    x = foo(something)
> except TypeError:
>    print "you should pass a sequence"
>    sys.exit()  # unrecoverable error
> except SoftException:
>    print "you passed an empty list"
> print x
>
> Am I close?
>
> But there's a problem. Once the SoftException is caught, execution will
> continue from the line "print x" -- but the function foo() never got a
> chance to actually return a result!

In that particular case above, you don't need to handle the Soft
Exception. As stated in it's original purpose, you don't need to
handle a Soft Exception, it exists there if you need to handle the
exceptional case, but ignorable on other cases. _IF_ printing the "you
passed an empty list" is an important operation, you'd make it like
this:
try:
   x = foo(something)
except TypeError:
   print "you should pass a sequence"
   sys.exit()  # unrecoverable error
except SoftException:
print "you passed an empty list"
x = 0
print x

or alternatively:

try:
   x = foo(something)
except TypeError:
   print "you should pass a sequence"
   sys.exit()  # unrecoverable error
except SoftException:
print "you passed an empty list"
else:
print x

The case you states above only mentions that you haven't fully grasped
the workflow in exception-based system.

> In order to make that work, you would need a significant change to
> Python's internals. I don't know how difficult that would be, but I'm
> guess that it would be a lot of work for not much benefit.

I too don't know how difficult that'd be, especially because the only
thing I know about Python's internal is it implements its garbage
collector by ref counting (which is barely useful here).

> But even if that happened, it would mean that the one mechanism has TWO
> different effects:
>
> try:
>     x = foo(sequence)
> except SoftException:
>     print x  # this is okay, because foo() did return
> except TypeError:
>     print x  # this is NOT okay, because foo() never returned
>
> That is a recipe for confusion.

Both are not okay since foo() never return on both cases (soft
statement doesn't return to finish the try clause except if explicitly
resumed).

(snip)
> > Perhaps relabeling it as Warning, and renaming raise SoftException as
> > give Warning might make it more acceptable?
>
> Do you realise that Python already has a warnings module?

Ah... I completely forget about it, but anyway the Warning module is
unrelated to this. Perhaps we could just think of another name, but
names doesn't seems to be important in Python modules anyway, can you
guess what pickle/zip/mutex/quopri/curses is if you're new to Python
without looking at the documentations? There are some modules in
Python that have weird names, we ought to reduce it, but we can't
reduce it... we ought to live with it.

(snip)
> > A possible solution to this problem might be to check whether distance
> > is less than P1.radius + P2.radius in the calculateforce. But, this
> > obfuscate the code since we have to separate distance calculation from
> > the main formula (see !s),
>
> I don't agree that this obfuscates the code.

For a formula as complex as this:
http://www.mapleprimes.com/blog/axel-vogt/computing-the-complex-gamma-function-using-spouges-formula
it might be useful to fragment the formula to smaller pieces

but in a simple to moderately complex that still fits in one line,
fragmenting the code confuses the eye.

> And here's a way to do it that doesn't calculate anything twice, and
> doesn't require any exceptions:
>
> def calculateforce(P1, P2, dist):
>     return (P1.mass - P2.mass)/dist
>
> And then for all pairs of particles:
>
> dist = distance(P1, P2)
> if dist <= P1.radius + P2.radius:
>     clump(P1, P2)
>     break
> F = calculateforce(P1, P2, dist)

That... is the worst solution that could ever be suggested. The
Particle objects already contain their own position, supplying dist
overrides their real distance of the particles and also it may make
bug holes by supplying bogus distance:
def calculateforce(P1, P2, dist):
return (P1.mass - P2.mass) / dist

calculateforce(P1, P2, 'bogus data')

or simply by passing dist that isn't equal (P1.X - P2.X) ** 2 + (P1.Y
- P2.Y) ** 2.

If you want to do it that way, it'd be much better 

Re: What c.l.py's opinions about Soft Exception?

[Lie]

On Mar 9, 9:29 pm, Kay Schluehr <[EMAIL PROTECTED]> wrote:
(snip)
> You are an appropriate person to consider the workflow in a dynamic
> language, no matter how the language is implemented internally.

I agree, but the only thing I'm not confident to talk about is how
it'll be implemented, since I think an idea should suggest how it can
be implemented in practice to show that it's not just a nonsense paper
idea that's not possible in reality.

> Just start with function calls
>
>    maybe_raise(ZeroDivisionError)
>
> The only requirement is that maybe_raise has to know when it shall
> raise ZeroDivisionError. This depends on whether the exception is
> caught. How do the program knows this in advance? There are no static
> analysis techniques available.

Perhaps similar technique the compiler uses to determine whether a
function is a normal function or a generator function? Positive
forward lookup for any soft exceptions, which would then activate
matching soft exceptions inside the code?

> When maybe_raise is entered the system must know that the exception is
> handled in the future. You can't inspect the call stack for this
> purpose because the call stack represents past events and
> continuations ( and you can't rely on names ).
>
> So you need something like this
>
>    do_softexception(ZeroDivisionError)
>    try:
>       TRY_BLOCK
>    except ZeroDivisionError:
>       EXCEPT_BLOCK
>
> But this looks odd and the solution isn't DRY. So better one macro-
> transforms a new statement into this form.

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Problems installing Python Imaging Library

[Nick Day]

Hi,

I'm trying to install PIL from source on my CentOS 4.5 server. The
build summary reports that I have everything installed...


PIL 1.1.6 BUILD SUMMARY

version   1.1.6
platform  linux2 2.3.4 (#1, Dec 11 2007, 05:28:55)
  [GCC 3.4.6 20060404 (Red Hat 3.4.6-9)]

--- TKINTER support ok
--- JPEG support ok
--- ZLIB (PNG/ZIP) support ok
--- FREETYPE2 support ok

... but if I try and build it I receive the following error:

/usr/bin/ld: /usr/local/lib/libjpeg.a(jcparam.o): relocation
R_X86_64_32 against `a local symbol' can not be used when making a
shared object; recompile with -fPIC

How do I fix this?  I am currently running "python setup.py build" and
don't understand how I would change the compiling options to add the "-
fPIC" flag.  I'm quite a newbie when it comes to Linux/Python so any
help you could give me would be great.

Thanks,
Nick
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Re: Changing the size of a Button

[Miki]

Hello Konrad,

> How do i change the size of a Button
> (using Tkinter), other than to set it
> during construction?
In Tkinter, usually the geometry managers (such as pack) are the ones
who size the widgets.
If you run something like:
import Tkinter as tk

root = tk.Tk()
def change_size():
b["text"] = "More text"

b = tk.Button(root, text="Text", command=change_size)
b.pack()

root.mainloop()

You'll see that the button changes size to accommodate the new text.

HTH,
--
Miki <[EMAIL PROTECTED]>
http://pythonwise.blogspot.com
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Re: Parse specific text in email body to CSV file

[Miki]

Hello,
>
 I have been searching all over for a solution to this. I am new to
> Python, so I'm a little lost. Any pointers would be a great help. I
> have a couple hundred emails that contain data I would like to
> incorporate into a database or CSV file. I want to search the email
> for specific text.
>
> The emails basically look like this:
>
> random text _important text:_15648 random text random text random text
> random text
> random text random text random text _important text:_15493 random text
> random text
> random text random text _important text:_11674 random text random text
> random text
> ===Date: Wednesday March 5, 2008
> name1: 15                name5: 14
>
> name2: 18                name6: 105
>
> name3: 64                name7: 2
>
> name4: 24                name8: 13
>
> I want information like "name1: 15" to be placed into the CSV with the
> name "name1" and the value "15". The same goes for the date and
> "_important text:_15493".
>
> I would like to use this CSV or database to plot a graph with the
> data.
import re

for match in re.finditer("_([\w ]+):_(\d+)", text):
print match.groups()[0], match.groups()[1]

for match in re.finditer("Date: ([^=]+)=", text):
print match.groups()[0]

for match in re.finditer("(\w+): (\d+)", text):
print match.groups()[0], match.groups()[1]


Now you have two problems :)

HTH,
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http://pythonwise.blogspot.com

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SV: Changing the size of a Button

[K Viltersten]

>> How do i change the size of a Button
>> (using Tkinter), other than to set it
>> during construction?
> In Tkinter, usually the geometry managers 
> (such as pack) are the ones who size the 
> widgets. If you run something like:
>import Tkinter as tk
> 
>root = tk.Tk()
>def change_size():
>b["text"] = "More text"
> 
>b = tk.Button(root, text="Text", command=change_size)
>b.pack()
> 
>root.mainloop()

Thanks for the answer.

Unfortunately, that won't help me at all, 
since i, apparently, asked the wrong 
question. Let me refrain myself.

What i wish to do is to affect the size 
of the button but not due to change of 
text but due to resize of the frame it
resides in.

This far i've managed to get a callback 
to a function as the resize occurs and to
print the sizes. However, i'd like to 
assign these values to the button so it 
always stays the same width as the frame.

--
Regards
Konrad Viltersten

sleep- a substitute for coffee for the poor
ambition - lack of sense to be lazy

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Re: gc question

[I V]

On Sun, 09 Mar 2008 01:57:38 -0800, Vince wrote:
> Well, that suits me. The most unnatural thing about Python was adapting
> to the idea of just letting unreleased resources go jogging off
> wherever. :)

Yes, that's a bad habit that garbage collection can encourage. GC is good 
for managing memory, but not good for managing other resources, so if an 
object holds some other resource, it's important to make sure the 
resource is released in a timely fashion rather than relying on the 
finalizer (the __del__ function).

CPython uses reference counting, so it usually destroys objects fairly 
soon after the stop being used. But JPython and IronPython don't do 
reference counting, so forgetting to clean up resources can be a 
significant problem.

> "Where's the f.close?"
> "You don't need it!"

Although, you still don't need f.close, with the new with statement:

with open('myfile') as f:
string = f.readline()
# f.close() gets called automatically here, without waiting for 
# garbage collection.

If you want to use this in 2.5, you have to write:

from __future__ import with_statement

The big advantage here is that f.close will get called if the block exits 
normally, or if there is an exception. For more, see 
http://effbot.org/pyref/with.htm .
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[ANN] pysqlite and APSW projects moved

[Gerhard Häring]

-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1

Dear pysqlite users!

I've moved both the pysqlite and APSW project to new homes.

pysqlite


web:http://oss.itsystementwicklung.de/trac/pysqlite aka http://pysqlite.org/
scm:pysqlite now uses a Mercurial repository
http://oss.itsystementwicklung.de/hg/pysqlite/

APSW


web:http://oss.itsystementwicklung.de/trac/apsw/
scm:Subversion: http://initd.org/svn/pysqlite/apsw/trunk/

Both pysqlite and APSW have a common mailing list at

http://itsystementwicklung.de/cgi-bin/mailman/listinfo/list-pysqlite

Existing subscribers that have not set the "nomail" flag have been moved to the
new list already.

- -- Gerhard

PS: Because of spam problems on the old Trac, I've patched AccountManager so
that you will now have to verify your human-ness with a captcha when you
register an account. The old Trac accounts were not moved on purpose to avoid
spam.

-BEGIN PGP SIGNATURE-
Version: GnuPG v1.4.6 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFH1C7tdIO4ozGCH14RAjAhAKCmxm+rKkjxMalCkH2Wjs88raxuCACgiV4B
XJq+YweOK0Zh1IWHLkrl3LI=
=b6zE
-END PGP SIGNATURE-
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Re: [pysqlite] [ANN] pysqlite and APSW projects moved

[Gerhard Häring]

-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1

Gerhard Häring wrote:
> [...] APSW
> 
> 
> web:http://oss.itsystementwicklung.de/trac/apsw/
> scm:Subversion: http://initd.org/svn/pysqlite/apsw/trunk/

That should have been http://oss.itsystementwicklung.de/svn/apsw/apsw/

- -- Gerhard
-BEGIN PGP SIGNATURE-
Version: GnuPG v1.4.6 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFH1DL7dIO4ozGCH14RAq4gAJ9tZuB9qcPERBkGzKEVBEx8nybfXgCeK8cX
V7sH3uAskDDNBuxYG34vExI=
=IXOx
-END PGP SIGNATURE-
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Re: SV: Changing the size of a Button

[Marc 'BlackJack' Rintsch]

On Sun, 09 Mar 2008 19:45:58 +0100, K Viltersten wrote:

> What i wish to do is to affect the size 
> of the button but not due to change of 
> text but due to resize of the frame it
> resides in.
> 
> This far i've managed to get a callback 
> to a function as the resize occurs and to
> print the sizes. However, i'd like to 
> assign these values to the button so it 
> always stays the same width as the frame.

Don't do it yourself, pack with the `fill` argument set to `Tkinter.X`.

Ciao,
Marc 'BlackJack' Rintsch
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Re: SV: Changing the size of a Button

[Peter Otten]

K Viltersten wrote:

> What i wish to do is to affect the size
> of the button but not due to change of
> text but due to resize of the frame it
> resides in.

This is done by the layout manager, too:
 
import Tkinter as tk

root = tk.Tk()
button = tk.Button(root, text="42")
button.pack(fill=tk.BOTH, expand=True)
root.mainloop()

Alternatively, with a grid layout:

button.grid(row=0, column=0, sticky="nsew")
root.rowconfigure(0, weight=1)
root.columnconfigure(0, weight=1)

Peter
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Re: Need Help Building PythonQt on Windows

[Diez B. Roggisch]

Jeff Schiller schrieb:
> I said "PythonQt" not PyQt.  That's an important distinction, I think :)
> 
> See http://pythonqt.sourceforge.net/

It sure is. Sorry, didn't realize the difference.

Diez
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Re: the way of "import"

[Gabriel Genellina]

En Sat, 08 Mar 2008 00:30:13 -0200, smalltalk <[EMAIL PROTECTED]>  
escribi�:

> I have three files names t1.py,t2.py,t3.py in e:\test\dir1,of course
> dir2 is exsit
> the content of t1.py as follow:
> t1.py
> import os
> print 'this is t1.py'
> os.chdir('..\\dir2')
> the content of t2.py as follow:
> print "this is t2.py"
> the content of t3.py as follow:
> import t1
> import t2
>
>
> if i run t3.py in cmd of windows as follow:
> python t3.py
>
> no errors show
>
> if i run t3.py in idle:
 import t3
> this is t1.py
> Traceback (most recent call las
>   File "", line 1, in 
>   File "t3.py", line 2, in 
> ImportError: No module named t2
>
> can you give me a help?

Which Python version? Which Windows version? With IDLE from Python 2.5.1  
on XP I don't get the error (and that's the right thing)

-- 
Gabriel Genellina

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Re: del class with recursive list

[duvo]

Thanks! I just need to remember to del the variables after "for in".

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Re: What c.l.py's opinions about Soft Exception?

[castironpi]

D'Aprano suggested callbacks.  How does this work for you?

class SomeNumeric(object):
def __div__(a, b):
if b == 0: raise ZeroDivisionError  ## Hard Exception...
if a == 0: msgboard- ZeroNumerator()
f = a / b
i = a // b
if f == float(i):
msgboard- IntegerDivision()
return a // b #? return i?
else:
msgboard- FloatDivision()
return a / b #? return f?


If it works, I can write some implementations of msgboard and discuss
its scope.

It sounded at one point like you were augmenting control flow, but you
cleared that up by saying, raise SoftException is not a true raise.
Correct?

There is a limit to how many behaviors you can fit in a single
statement in any language.  What behaviors is determined by other
choices in the language design.  Those choices have many consequences,
some linguistic, some social, and some personal.  If a dictator always
makes impersonal decisions, which linguistic + social ones should he
make?  If the answer is, "No, we will not strike note J and K because
we elected to strike notes L and M instead", then it's disappointing,
but it might ease that to know what L and M are.

Lastly, that notation I wrote was kind of sly.  I might favor
msgboard( ZeroNumerator() ) or even msgboard.add( ZeroNumerator() ).

How far are you willing to come from the OP's proposal to get it to
work?  If they add something half-way there, but you don't get exactly
what you want, is that fair?
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__iter__ yield

[duccio]

Hello!
Someone knows if it's possible to make this __iter__ function with just  
one 'yield' intead of two?
Is there some simpler way to make this  __iter__ iter through all nodes?
Thanks!

class Node:
 def __init__(self, data=None):
 self.childs=[]
 self.data=data
 def appendNode(self, n):
 node=Node(n)
 self.childs.append(node)
 return node
 def __str__(self):
 return '<'+str(self.data)+'>'
 def __iter__(self):
 yield self #1
 for n in self.childs:
 for nn in n.__iter__():
 yield nn #2

n=Node()
n.appendNode(1).appendNode(2).appendNode(3).appendNode(4)
n.appendNode(11).appendNode(22).appendNode(33).appendNode(44)
for node in n:
 print node
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Re: Checking if a variable is a dictionary

[castironpi]

On Mar 9, 9:23 am, Steven D'Aprano <[EMAIL PROTECTED]
cybersource.com.au> wrote:
> On Sun, 09 Mar 2008 06:58:15 -0700, Guillermo wrote:
> > Okay, so I think I know where's the catch now -- you must rely on the
> > fact that the protocol is implemented, there's no way to enforce it if
> > you're expecting a parrot-like object. You'd try to call the speak()
> > method and deal with the error if there's no such method?
>
> That's right. That's called "duck typing" -- if all you want is something
> that quacks like a duck, then it doesn't matter if it actually is a duck
> or not.
>
> Or if you prefer: if it quacks like a duck and swims like a duck, then
> it's close enough to a duck as to make no difference.

The syntax checker over here raised a warning on this one.  "So close
to a duck as."  (I'm using the so...as construct in my Propositional
Calculus program.)

> try:
>     something.speak
> except AttributeError:
>     # No speak() method, so it can't be a parrot.
>     do_something_else()

It might be a dead parrot.  HAR!

> else:
>     # It seems to follow the parrot protocol.
>     yummy_goodness = something.speak(5)
>     assert "spam" in yummy_goodness.lower()

P.S.  Is 'resemblant' a word?  So resemblant of a duck as.
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Re: parralel downloads

[castironpi]

> > > >>  my problem is that I would like to download several files at the time.
> > > >>  As I have not much experience in programming, could you point me the
> > > >>  easier ways to do this in python ?
>
> > Thank you both for your help. Threads are working for me. However, a
> > new problem for me is that the url I want to download are in an xml
> > file (I want to download podcasts), and is not the same as the file
> > downloaded:
>
> >http://www.sciam.com/podcast/podcast.mp3?e_id=86102326-0B1F-A3D4-74B2...
>
> > will be redirected to download:
>
> >http://podcast.sciam.com/daily/sa_d_podcast_080307.mp3
>
> > is there a way, knowing the first url to get the second at runtime in
> > my script ?
>
> Found it: geturl() does the job

That's for normalizing schemes.  I believe you subclass FancyURLopener
and override the read method.
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Re: parralel downloads

[Gabriel Genellina]

En Sat, 08 Mar 2008 14:47:45 -0200, Gary Herron  
<[EMAIL PROTECTED]> escribi�:

> poof65 wrote:
>> For your problem you have to use threads.
>>
> Not at all true.  Thread provide one way to solve this, but another is
> the select function.  For this simple case, select() may (or may not) be
> easier to write.  Pseudo-code would look something like this:
>
>   openSockets = list of sockets one per download file:
>   while openSockets:
> readySockets = select(openSockets ...) # Identifies sockets with
> data to be read
> for each s in readSockets:
>   read from s and do whatever with the data
>   if s is at EOF: close and remove s from openSockets
>
> That's it.  Far easier than threads.

Easier? If you omit all the relevant details, yes, looks easy. For  
example, you read some data from one socket, part of the file you're  
downloading. Where do you write it? You require additional structures to  
keep track of things.
Pseudocode for the threaded version, complete with socket creation:

def downloadfile(url, fn):
   s = create socket for url
   f = open filename for writing
   shutil.copyfileobj(s.makefile(), f)

for each url, filename to retrieve:
   t = threading.Thread(target=downloadfile, args=(url,filename))
   add t to threadlist
   t.start()

for each t in threadlist:
   t.join()

The downloadfile function looks simpler to me - it's what anyone would  
write in a single threaded program, with local variables and keeping full  
state.
The above pseudocode can be converted directly into Python code - no more  
structures nor code are required.

Of course, don't try to download a million files at the same time -  
neither a million sockets nor a million threads would work.

-- 
Gabriel Genellina

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Re: Regarding coding style

[castironpi]

On Mar 8, 7:51 pm, Steven D'Aprano <[EMAIL PROTECTED]
cybersource.com.au> wrote:
> On Sat, 08 Mar 2008 13:40:56 -0800, dave_mikesell wrote:
> > On Mar 8, 2:27 pm, [EMAIL PROTECTED] wrote:
>
> >> Good comments are better than bad names. Good names are better than bad
> >> comments.
>
> > If you're taking the time to write good comments, why not just fix the
> > bad names?  The compiler/interpreter can never, ever catch bad comments.
>
> Yes, but the Python compiler can only catch bad names if you do this at
> the top of every module:
>
> import semantic_analysis
> import magic.crystal_ball.read_programmers_mind

dir( magic )!
dir( magic.crystal_ball )?
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Re: Regarding coding style

[castironpi]

On Mar 9, 4:25 am, Lie <[EMAIL PROTECTED]> wrote:
> On Mar 9, 3:27 am, [EMAIL PROTECTED] wrote:
>
> > To Lie:
>
> > > Personally I preferred a code that has chosen good names but have
> > > little or no comments compared to codes that makes bad names and have
>
> > Personally I don't.  Show me a good one.  Until you do, it's not that
> > I won't like it, it's that I can't.  You know, in linguistics, there's
>
> But I much prefer it that the code has good names AND concise
> comments, not too short and not too long that it becomes obscure.

What do you mean?  If 'obscure' is the right word, then it's
subjective (from metrics import obscurity?), which means that 10% of
the people disagree with you, or 90% do.  The end-all be-all, there is
no such thing.  I don't think it's obscure; I do.  Is it?
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execute

[Gif]

i'm trying to execute a file without replacing the current process,
but after searching the help file, documentations and the web, i can't
a way of doing that.

os.exec*() will close the current program.

ps: by executing i mean like typing "mspaint" in run dialog.. it's not
a python file
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1.5.2 and functools or similar

[Troels Thomsen]

Hello,

I am writing a simple delayed-call mechanism , that is causing a bit of 
headache. Works like this:

myPrint(s)
  print "..." + s

myTimer.add(myPrint , "hello" , 15)

This means that the myprint function is called in 15 seconds with the 
parameter "hello".
The housekeeping of these timers is called by the main loop of the "os"

This works well but i would like to be able to use it with any number of 
parameters

Functools is not a part of the 1.5.2+ python that I am running on (embedded 
device),
so i tried to pass the parameters as a tuple like this

myTimer.add(myAdder , (3,6) , 15)

and the housekeeping function would then call the function like this

def updateTimers()
  for timerItm in timerTable:
  ...

  
timerItm.func(*timerItm.parameters)

Works well on python 2.5 but not on 1.5.2 (?)


Current solution is to have default parameters None for the add function

def add( func , timeout , param1 = None , param2 = None)

And the update function then checks if parameters is specified

def updateTimers()
  for timerItm in timerTable:
  ...

  
  # ugly part :
  if timerItm.param1 is not None and timerItm.param2 is not None:
timerItm.func(timerItm.param1, timerItm.param2) # two parameters
  elif ..
timerItm.func(timerItm.param1) # one parameter
  else
timerItm.func() # no parameters

This has the implication that I can not call a function with the parameter 
None if I wanted to.
(not a huge problem)

Right now it works quite well with up to two parameters, it covers 99% of 
usage. If I need to call a function with more parameters, i can always write 
a wrapper function for it. Wondering if anyone had some sugestions ?


By the way, is it bad style to check for object identity instead of value 
"None".
What aboutt integers ? if value is 0: ..
I guess it is implementation specific / could change in future versions ?


Thx,
Troels









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Logically/Selectively Sub Class?

[xkenneth]

Might be a silly question, but is it possible to selectively subclass,
IE subclass is a supporting module is present and not otherwise.

Regards,
Kenneth Miller
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Re: execute

[Gif]

i know os.popen() but i want to execute a file with args
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Re: execute

[Gif]

ok i found a workaround.
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Re: Logically/Selectively Sub Class?

[Diez B. Roggisch]

xkenneth schrieb:
> Might be a silly question, but is it possible to selectively subclass,
> IE subclass is a supporting module is present and not otherwise.

Yes, something like this should work

class Foo(some, base, classes)
pass

if condition:
Temp = Foo
class Foo(Temp, otherclass): pass


Alternatively, you can use the type-function to create classes explicit 
with a list of base-classes.

However it smells after bad design... what's your actual usecase?

Diez
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Re: execute

[Dan Upton]

On Sun, Mar 9, 2008 at 5:22 PM, Gif <[EMAIL PROTECTED]> wrote:
> i'm trying to execute a file without replacing the current process,
>  but after searching the help file, documentations and the web, i can't
>  a way of doing that.
>
>  os.exec*() will close the current program.
>
>  ps: by executing i mean like typing "mspaint" in run dialog.. it's not
>  a python file

On *nix, you can use os.fork().  According to
http://effbot.org/librarybook/os.htm , you can use os.spawn to
accomplish a similar effect on Windows, although I haven't used it.
Also, you might check the subprocess module --
http://docs.python.org/lib/module-subprocess.html .

-dan
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Re: 1.5.2 and functools or similar

[castironpi]

On Mar 9, 4:26 pm, "Troels Thomsen"  wrote:
> Hello,
>
> I am writing a simple delayed-call mechanism , that is causing a bit of
> headache. Works like this:
>
> myPrint(s)
>   print "..." + s
>
> myTimer.add(myPrint , "hello" , 15)
>
> This means that the myprint function is called in 15 seconds with the
> parameter "hello".
> The housekeeping of these timers is called by the main loop of the "os"
>
> This works well but i would like to be able to use it with any number of
> parameters
>
> Functools is not a part of the 1.5.2+ python that I am running on (embedded
> device),
> so i tried to pass the parameters as a tuple like this
>
> myTimer.add(myAdder , (3,6) , 15)
>
> and the housekeeping function would then call the function like this
>
> def updateTimers()
>   for timerItm in timerTable:
>   ...
>     
>       
>         timerItm.func(*timerItm.parameters)
>
> Works well on python 2.5 but not on 1.5.2 (?)
>
> Current solution is to have default parameters None for the add function
>
> def add( func , timeout , param1 = None , param2 = None)
>
> And the update function then checks if parameters is specified
>
> def updateTimers()
>   for timerItm in timerTable:
>   ...
>     
>       
>       # ugly part :
>       if timerItm.param1 is not None and timerItm.param2 is not None:
>         timerItm.func(timerItm.param1, timerItm.param2) # two parameters
>       elif ..
>         timerItm.func(timerItm.param1) # one parameter
>       else
>         timerItm.func() # no parameters
>
> This has the implication that I can not call a function with the parameter
> None if I wanted to.
> (not a huge problem)
>
> Right now it works quite well with up to two parameters, it covers 99% of
> usage. If I need to call a function with more parameters, i can always write
> a wrapper function for it. Wondering if anyone had some sugestions ?
>
> By the way, is it bad style to check for object identity instead of value
> "None".
> What aboutt integers ? if value is 0: ..
> I guess it is implementation specific / could change in future versions ?
>
> Thx,
> Troels

def g( arg1, arg2 ):
   print( arg1, arg2 )
   return arg1

def h( arg1 ):
   print( arg1 )
   return arg1

def caller( fun, *args, **kwargs ):
   return fun( *args, **kwargs )

print( caller( g, 'abc', 'def' ) )
print( caller( h, 'abc' ) )

'''
abc def
abc
abc
abc
'''
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Re: Logically/Selectively Sub Class?

[xkenneth]

On Mar 9, 4:38 pm, "Diez B. Roggisch" <[EMAIL PROTECTED]> wrote:
> xkenneth schrieb:
>
> > Might be a silly question, but is it possible to selectively subclass,
> > IE subclass is a supporting module is present and not otherwise.
>
> Yes, something like this should work
>
> class Foo(some, base, classes)
>     pass
>
> if condition:
>     Temp = Foo
>     class Foo(Temp, otherclass): pass
>
> Alternatively, you can use the type-function to create classes explicit
> with a list of base-classes.
>
> However it smells after bad design... what's your actual usecase?
>
> Diez

Yeah, it's really a non-issue, just more a curiosity. I'm using ZODB
for a lot of my stuff now, and I need my objects to be persistent,
however there might be a case where my classes could be used in a non-
persistent manner. I'll just have ZODB as a requirement for my
package.

Regards,
Kenneth Miller
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Re: Logically/Selectively Sub Class?

[castironpi]

On Mar 9, 4:28 pm, xkenneth <[EMAIL PROTECTED]> wrote:
> Might be a silly question, but is it possible to selectively subclass,
> IE subclass is a supporting module is present and not otherwise.
>
> Regards,
> Kenneth Miller

if mod is present:
   class Waypoint( Mine, Yours ): pass
else:
   class Waypoint( Mine ): pass

class NewClass( Waypoint ).

In 3.0, you can do

if mod is present:
   bases= Mine, Yours
else:
   bases= Mine,

class NewClass( *bases ).
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Re: What c.l.py's opinions about Soft Exception?

[Diez B. Roggisch]

> Perhaps similar technique the compiler uses to determine whether a
> function is a normal function or a generator function? Positive
> forward lookup for any soft exceptions, which would then activate
> matching soft exceptions inside the code?

The difference between generators and functions is made on the 
yield-keyword.

However, the exception-mechanism isn't governed by the compiler, but at 
runtime. You can do things like this:


eclass = HardException if full_moon() else: SoftException

raise eclass()

Which means that you don't stand a chance determining 
soft-exception-usage at compiletime.

What would work is most probably to register soft-exception-handlers 
when encountering them at runtime, thus making raising-code aware of 
them and execute it only if there are one (or several) present.

However, IMHO it's not a worthy extension to the language - for the same 
reasons Steven gave. It seems only useful for tightly coupled code, not 
as a general mechanism. And callbacks or maybe even thread-local state 
are sufficient to deal with that I'd say.


Diez
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Re: Logically/Selectively Sub Class?

[Diez B. Roggisch]

xkenneth schrieb:
> On Mar 9, 4:38 pm, "Diez B. Roggisch" <[EMAIL PROTECTED]> wrote:
>> xkenneth schrieb:
>>
>>> Might be a silly question, but is it possible to selectively subclass,
>>> IE subclass is a supporting module is present and not otherwise.
>> Yes, something like this should work
>>
>> class Foo(some, base, classes)
>> pass
>>
>> if condition:
>> Temp = Foo
>> class Foo(Temp, otherclass): pass
>>
>> Alternatively, you can use the type-function to create classes explicit
>> with a list of base-classes.
>>
>> However it smells after bad design... what's your actual usecase?
>>
>> Diez
> 
> Yeah, it's really a non-issue, just more a curiosity. I'm using ZODB
> for a lot of my stuff now, and I need my objects to be persistent,
> however there might be a case where my classes could be used in a non-
> persistent manner. I'll just have ZODB as a requirement for my
> package.

Ah. Then this also might work

try:
from ZODB import Persistent
except ImportError:
class Persistent: pass

Diez
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Re: __iter__ yield

[Diez B. Roggisch]

duccio schrieb:
> 
> Hello!
> Someone knows if it's possible to make this __iter__ function with just 
> one 'yield' intead of two?
> Is there some simpler way to make this  __iter__ iter through all nodes?
> Thanks!
> 
> class Node:
> def __init__(self, data=None):
> self.childs=[]
> self.data=data
> def appendNode(self, n):
> node=Node(n)
> self.childs.append(node)
> return node
> def __str__(self):
> return '<'+str(self.data)+'>'
> def __iter__(self):
> yield self #1
> for n in self.childs:
> for nn in n.__iter__():
> yield nn #2

Nope. There have been numerous discussions about this, introducing 
something like a yield_all-keyword or such thing that would replace the 
above boilerplate - but so far they all have been rejected. Search the 
archives for the reasons, I don't remember them :)

Diez
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Re: Regarding coding style

[castironpi]

> > >> Good comments are better than bad names. Good names are better than bad
> > >> comments.
>
> > > If you're taking the time to write good comments, why not just fix the
> > > bad names?  The compiler/interpreter can never, ever catch bad comments.
>
> > Yes, but the Python compiler can only catch bad names if you do this at
> > the top of every module:
>
> > import semantic_analysis
> > import magic.crystal_ball.read_programmers_mind
>
> dir( magic )!
> dir( magic.crystal_ball )?

Someone should try annotating code with a dictionary lookup on
identifiers.  Anyone bored on Fridays?  No one should try printing out
the definitions in real-time as the code is executing.
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Re: Need Help Building PythonQt on Windows

[Martin v. Löwis]

> Since I'm new to compiling Qt with mingw and completely new to python,
> I was hoping for tips on why I'm getting these errors.  If anyone has
> a better suggestion for a forum/mailing list then please let me know.

These symbols are all from pythonxy.dll. You need to add the 
corresponding import library (libpythonxy.a/pythonxy.lib) into
the linker line, using a -l option.

Regards,
Martin
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Re: 1.5.2 and functools or similar

[Paul Rubin]

"Troels Thomsen"  writes:
> timerItm.func(*timerItm.parameters)
> 
> Works well on python 2.5 but not on 1.5.2 (?)

I think in 1.5.2 the *args notation wasn't present and you had to say:

   apply(timerItm.func, timerItm.parameters)
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Re: __iter__ yield

[Paul Hankin]

On Mar 9, 8:58 pm, duccio <[EMAIL PROTECTED]> wrote:
> Someone knows if it's possible to make this __iter__ function with just  
> one 'yield' intead of two?
> ...
>      def __iter__(self):
>          yield self #1
>          for n in self.childs:
>              for nn in n.__iter__():
>                  yield nn #2

Only one yield and shorter (but not really any simpler):

from itertools import chain

class Node:
...
def __iter__(self):
for x in chain([self], *self.childs):
yield x

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Distributed App - C++ with Python for Portability?

[Roopan]

Hello!

I am looking at developing an enterprise-grade distributed data
sharing application - key requirements are productivity and platform
portability.

Will it be sensible to use C++ for performance-critical sections and
Python for all the glue logic.

Pls comment from your *experiences* how Python scales to large
projects( > 200KLOC).
I assume the C++/Python binding is fairly painless.

Regards
Elam.
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Re: execute

[castironpi]

> >  os.exec*() will close the current program.
>
> On *nix, you can use os.fork().  According 
> tohttp://effbot.org/librarybook/os.htm, you can use

Do you mean, and block for the process to terminate?  Or do you mean,
do something else in the meantime, perhaps for a certain amount (of
meantime)?

[Enter event loops.  Exeunt.]

P.S.  What do you do if you think of a comeback for something from a
week ago on the newsgroup?

P.P.S.  Why are you thinking of comebacks on a newsgroup besides
alt.flame?

P.P.P.S.  Anyone read alt.tasteless?
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Re: Beautiful Code in Python?

[castironpi]

On Mar 2, 1:18 pm, [EMAIL PROTECTED] wrote:
> On Mar 2, 12:01 pm, John DeRosa <[EMAIL PROTECTED]> wrote:
>
> > On Mon, 3 Mar 2008 01:23:32 +0900, js <[EMAIL PROTECTED]> wrote:
> > >Hi,
>
> > >Have you ever seen Beautiful Python code?
> > >Zope? Django? Python standard lib? or else?
>
> > >Please tell me what code you think it's stunning.
>
> > Just about any Python code I look at.
>
> Decorators, with, and namedtuple.

Oh yeah, and variable arguments and keyword
dictionaries.
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Re: Intra-Package References

[Gabriel Genellina]

En Sat, 08 Mar 2008 17:36:12 -0200, xkenneth <[EMAIL PROTECTED]> escribió:

> Does your python module have to exist in the path in order for intra-
> package references to work?

No, but Python must be aware that the importing module is inside a  
package. So the script being executed (main) should live outside the  
package.

-- 
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Re: 1.5.2 and functools or similar

[Terry Reedy]

"Troels Thomsen" <"nej tak..."@bag.python.org> wrote in message 
news:[EMAIL PROTECTED]
| def updateTimers()
|  for timerItm in timerTable:
|  ...
|
|  
|timerItm.func(*timerItm.parameters)
|
| Works well on python 2.5 but not on 1.5.2 (?)

apply(timerItm.func, timerItm.parameters) # see
http://docs.python.org/lib/non-essential-built-in-funcs.html
apply disappears in 3.0

tjr



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Re: Returning values from function to Python shell/IPython

[castironpi]

> >  > well after all it's a function so the only ways you can get things out
> >  > of it are:
> >  > - return a dict with all the objects
> >  > - use global (very messy)
> >  > - use a decorator to do either of the above.
>
> >  Messy, all of those... :(.
>
> >  > on the other hand have you consider using a proper test package?
> >  > instead of inspecting the objects manually from the shell you could
> >  > make it all automatic. with assert statements. you could use the std.
> >  > python testing moduleshttp://docs.python.org/lib/development.htmlor
> >  > something less verbosed like nose
>
> >  Usually, I'm using standard Python testing modules, but sometimes that is
> >  just an overkill. Sometimes I like to do 'exploratory programming',
> >  especially in the early phases of development - create a bunch of objects I
> >  want to play with and do that from IPython. Only way I found out to
> >  somewhat automate this procedure is to have a function that creates all of
> >  the test objects, and then raises an exception at the end. IPython starts
> >  ipdb, so I can work with the objects the function created (without copying
> >  them back to the shell). But this somehow looks too hack-ish for me, so I
> >  was wondering if there was an alternative...
>
> ohhh if that is the case then what you are doing seems to be the
> optimal. Just have module lvl code ran the testing in fact I don't
> even put those into the if __name__, the reason is that this is just
> temp testing that will later become real unit testing, and will never
> hit a production app. it gives you the most flexibility.

While you're at it, can you call up prior source, and edit it?  BASIC
had line numbers:

10 def f( a ):
20   return a+ 1

>>> 15 print( a )

10 def f( a ):
15 print( a )
20   return a+ 1

>>> 15   print( a )

10 def f( a ):
15   print( a )
20   return a+ 1

'''Interactives could some day have this too:'''

>>> edit f
Object f opened in editor
>>> close
Object f written back.  Elapsed time 5 minutes.
>>>
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Re: What c.l.py's opinions about Soft Exception?

[castironpi]

On Mar 9, 4:51 pm, "Diez B. Roggisch" <[EMAIL PROTECTED]> wrote:
> > Perhaps similar technique the compiler uses to determine whether a
> > function is a normal function or a generator function? Positive
> > forward lookup for any soft exceptions, which would then activate
> > matching soft exceptions inside the code?
>
> What would work is most probably to register soft-exception-handlers
> when encountering them at runtime, thus making raising-code aware of
> them and execute it only if there are one (or several) present.
>
> [HO snip]

Mr. Roggisch, I just said that.  You can unplonk me now.
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any chance regular expressions are cached?

[mh]

I've got a bit of code in a function like this:

s=re.sub(r'\n','\n'+spaces,s)
s=re.sub(r'^',spaces,s)
s=re.sub(r' *\n','\n',s)
s=re.sub(r' *$','',s)
s=re.sub(r'\n*$','',s)

Is there any chance that these will be cached somewhere, and save
me the trouble of having to declare some global re's if I don't
want to have them recompiled on each function invocation?

Many TIA!
Mark

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Re: parralel downloads

[castironpi]

> > That's it.  Far easier than threads.

I'll order a 'easyness' metric from the warehouse.  Of course,
resources are parameters to the metric, such as facility given lots of
time, facility given lots of libraries, facility given hot shots, &c.

> Easier? If you omit all the relevant details, yes, looks easy. For  
>
> def downloadfile(url, fn):
>    s = create socket for url
>    f = open filename for writing
>    shutil.copyfileobj(s.makefile(), f)
>
> for each url, filename to retrieve:
[ threadlist.addandstart( threading.Thread(target=downloadfile,
args=(url,filename)) ) ]
>
[ threadlist.joineach() ]

> Of course, don't try to download a million files at the same time -  
> neither a million sockets nor a million threads would work.

Dammit!  Then what's my million-core machine for?  If architectures
"have reached the point of diminishing returns" ( off py.ideas ), then
what's the PoDR for numbers of threads per core?

Answer: One.  Just write data structures and don't swap context.  But
when do you want it by?  What is the PoDR for amount of effort per
clock cycle saved?  Get a Frank and a Brit and ask them what language
is easiest to speak.

(Answer: Math.  Har *plonk*.)
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Re: any chance regular expressions are cached?

[Tim Chase]

> s=re.sub(r'\n','\n'+spaces,s)
> s=re.sub(r'^',spaces,s)
> s=re.sub(r' *\n','\n',s)
> s=re.sub(r' *$','',s)
> s=re.sub(r'\n*$','',s)
> 
> Is there any chance that these will be cached somewhere, and save
> me the trouble of having to declare some global re's if I don't
> want to have them recompiled on each function invocation?


 >>> import this
...
Explicit is better than implicit
...


Sounds like what you want is to use the compile() call to compile 
once, and then use the resulting objects:

   re1 = re.compile(r'\n')
   re2 = re.compile(r'^')
   ...
   s = re1.sub('\n' + spaces, s)
   s = re2.sub(spaces, s)
   ...


The compile() should be done once (outside loops, possibly at a 
module level, as, in a way, they're constants) and then you can 
use the resulting object without the overhead of compiling.

-tkc



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Re: Timed execution in eval

[castironpi]

> >  > and I want to be able to stop [functions] if they run too long.
>
> > That's tricky [due to a synthetic limitation].

It would suck if you couldn't hold the GIL for as long as you need
to.  But how much is it used?

Wrote the docs:
> when two threads simultaneously increment the reference count of the same 
> object

Well, the example sucked.  Just synchronize ref count manipulation.
Every OS has locking primitives, and a library exists to deny requests
to block that lock dead.  How integral is the GIL to Python?

> The Python interpreter is not fully thread safe

-Make- it so.
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RE: any chance regular expressions are cached?

[Ryan Ginstrom]

> On Behalf Of Tim Chase
> Sounds like what you want is to use the compile() call to 
> compile once, and then use the resulting objects:
> 
>re1 = re.compile(r'\n')
>re2 = re.compile(r'^')
>...
>s = re1.sub('\n' + spaces, s)
>s = re2.sub(spaces, s)

Yes. And I would go a step further and suggest that regular expressions are
best avoided in favor of simpler things when possible. That will make the
code easier to debug, and probably faster.

A couple of examples:
>>> text = """spam spam spam
spam spam


 spam

spam"""
>>> # normalize newlines
>>> print "\n".join([line for line in text.splitlines() if line])
spam spam spam
spam spam
 spam
spam
>>> # normalize whitespace
>>> print " ".join(text.split())
spam spam spam spam spam spam spam
>>> # strip leading/trailing space
>>> text = "  spam  "
>>> print text.lstrip()
spam  
>>> print text.rstrip()
  spam
>>> print text.strip()
spam

Regards,
Ryan Ginstrom

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Re: Timed execution in eval

[castironpi]

> Write the docs:
>
> > when two threads simultaneously increment the reference count of the same 
> > object
>
> Well, the example sucked.  Just synchronize ref count manipulation.
> Every OS has locking primitives, and a library exists to deny requests
> to block that lock dead.  How integral is the GIL to Python?
>
> > The Python interpreter is not fully thread safe
>
> Make it so.

Per-thread reference counts do the trick.
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python-2.5.2 src rpm

[Donald Raikes]

Hello,

I am trying to install python 2.5.2 onto enterprise linux, and would like to 
start with a source rpm package so that I can build the package locally and 
make sure I have all necessary dependencies.

I have been unable to locate a source rpm package for python 2.5.2 or any 
version of 2.5 for that matter.

Any pointers would be appreciated.



  

Donald Raikes | Accessibility Specialist
Phone: +1 602 824 6213 | Fax: +1 602 824 6213 | Mobile: +1 520 271 7608 
Oracle JDeveloper QA

  
"Please
 consider your environmental responsibility before printing this e-mail"

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Re: Uninstalling Eggs

[Mike Driscoll]

On Mar 9, 8:30 am, PB <[EMAIL PROTECTED]> wrote:
> I just installed the Shove module with the monumentally crap
> setuptools. Whilst the install succeeded, imports now trigger errors,
> so clearly it did not install correctly. Can I simply delete the .egg
> file from my lib/python2.3/site-packages/ directory?
>
> Cheers,

Deleting the shove-egg folder is definitely the recommended and
easiest way I know of to "uninstall" an egg. I've used it successfully
before.

Mike
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Python 2.5 segmentation faulting importing random

[Bagpussnz]

Hi,
Whenever I try to import random in a python module, I get a
segmentation fault.

I've traced it using,
import pdb
pdb.set_trace()
import random

When it gets to..

> /usr/lib/python2.5/random.py(57)()
-> LOG4 = _log(4.0)

It seg faults.

I'm running on OpenSuse 10.2.
Linux devhost 2.6.18.8-0.7-bigsmp #1 SMP Tue Oct 2 17:21:08 UTC 2007
i686 i686 i386 GNU/Linux

The python header says..
Python 2.5 (r25:51908, May 25 2007, 16:14:04)
[GCC 4.1.2 20061115 (prerelease) (SUSE Linux)] on linux2

Any ideas?
Regards,
Ian.
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Re: any chance regular expressions are cached?

[Terry Reedy]

<[EMAIL PROTECTED]> wrote in message 
news:[EMAIL PROTECTED]
| I've got a bit of code in a function like this:
|
|s=re.sub(r'\n','\n'+spaces,s)
|s=re.sub(r'^',spaces,s)
|s=re.sub(r' *\n','\n',s)
|s=re.sub(r' *$','',s)
|s=re.sub(r'\n*$','',s)
|
| Is there any chance that these will be cached somewhere, and save
| me the trouble of having to declare some global re's if I don't
| want to have them recompiled on each function invocation?

The last time I looked, several versions ago, re did cache.
Don't know if still true.  Not part of spec, I don't think.

tjr



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Re: Solve a Debate

[castironpi]

> days_in_month 12:
> 31
> 30
> 28
> 31
> ...
> 30
> 31
> assign $days days_in_month[$month]
>
> This program consists of 2 operations (table jump and assignment)
> and 12 values. This makes a memory consumption of 12+2 = 14

Along the same lines, you could populate the table somewhat sparsely,
and goto a modulo key.

You could even put functions in it:

setreturn $endoftable
hash month
goto
-0
-1
-2
jan.-> 3: setvjmp janfun
-4
-5
apr.-> 6: setvjmp aprfun
$endoftable

Sweet!  Are you stack-ops?
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Import - interpreter works but .py import does not

[John Boy]

First post and very much a newbie to Python. Have 2.5 on Linux (GG). I
think I have set up PYTHONPATH correctly in that I can import a module
apply_bp and it complains about line 20 in apply_bp which is:

import sys, aipy, numpy, os

At the interpreter prompt, however, I can import sys, numpy etc. and
can do dir() and see the entry points so I think my overall
installation is OK.

Why does line not work ? Also I would have thought that when I pre-
imported sys et al that they would be in the symbol table so that the
import line would be a noop.

  Thanks,

 Slainte,

John
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