Re: Advice to a Junior in High School?

[collegebabe2004]

wow! Aren't we getting ahead of ourselves?  Well, I'm glad you are
beefing up your college knowledge but let's just sit back for a minute
and breathe..there, feel better? Now, listen.  When I was a
freshman and sophomore in high school I was so sure I wanted to be an
artist and attend one of the most highly recognized and expensive art
schools in the country. I wanted to go to college back east away from
my parents.  Now I'm a psychology major in community college and I want
to attend UCLA!  First of all, NEVER SETTLE FOR LESS when it comes to
your major.  Do what it is true to your heart and never let people say
you can't! You can double major if you want to be on the safe side.
Compsci isn't an easy thing to do as you know and it's a highly
regarded profffession! By the time you graduate college, the world
could be a completely different place. But let's just worry about here
and now.  If you think too much about the future IT WILL DRIVE YOU
CRAZY!  Trust me, you are doing everything right so far.  I applaud
your effort but relax and everything will fall into place eventually!
I would suggest taking Japanese because you will have to work with them
eventually if you do decide to choose compsci as your proffesion.
Margaux

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Re: lambda

[Antoon Pardon]

Op 2005-01-17, Just schreef <[EMAIL PROTECTED]>:
> In article <[EMAIL PROTECTED]>,
>  Antoon Pardon <[EMAIL PROTECTED]> wrote:
>
>> >> I don't see a big difference between these principles
>> >> and the hash key principle,
>> >
>> > Than you haven't looked hard enough.
>> 
>> All of these can get unexpected behaviour because of the
>> assignment-doesn't-copy semantics. The same semantics
>> that can cause problems if you work with mutable dictionary
>> keys.
>
> Again, the difference is:
>
>   1. assigning mutable objects *can* cause unexpected behavior
>  (however, it's a useful feature, everyone using Python
>  for longer than a day or two knows this, and then it's
>  *expected* behavior.
>
>   2. mutating dict keys *does* *always* cause problems.
>  (unless you use an identity hash/cmp)

3 mutating an item in a sorted list *does* *always* cause problems

4 mutating an item in a heap queue *does* *always* cause problems

> It's nonsense to forbid 1) since it's a useful feature. It's useful to 
> forbid ("discourage") 2) since mutating dict keys is seldom useful (and 
> when it is, Python lets you support it in your own objects).

Yes mutating dict keys is seldom usefull. But again you are conflating
mutable dict keys with mutating dict keys. No mutables as dict keys
means you can't mutate the object even if it is not a key. But whether
assigning mutable objects is usefull or not doesn't depend on whether
the object will also be usefull as a key or not. You treat this as
if an obejct is always a key or never and then decide mutable objects
as dict keys is not usefull because mutating keys is not usefull.

More specific the Decimal class is mutable and usable as dict key.

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Re: wxPython and PyGame - do they play well together?

[Terry Reedy]

"Erik Bethke" <[EMAIL PROTECTED]> wrote in message 
news:[EMAIL PROTECTED]
> I am having a great time with python and pygame, and last night I took
> a long look at the wxPython demo.  I think that rocks as well.
>
> So now, my question is do wxPython and PyGame work together?

I have no personal experience, but based on posts to the Pygame mailing 
list, also accessible via Google or as newsgroup thru Gmane (where I read 
it), the answer is yes.  The subject of Pygame with guis has been discussed 
in the past couple of months.  I recommend that you read the archives for 
the recent past and then join the list or subscribe via gmane or google. 
It is a low volume, low noise, list.

Terry J. Reedy



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Re: Fuzzy matching of postal addresses

[Aaron Bingham]

Andrew McLean wrote:
I have a problem that is suspect isn't unusual and I'm looking to see if 
there is any code available to help. I've Googled without success.

Basically, I have two databases containing lists of postal addresses and 
need to look for matching addresses in the two databases. More 
precisely, for each address in database A I want to find a single 
matching address in database B.
I had a similar problem to solve a while ago.  I can't give you my code, 
but I used this paper as the basis for my solution (BibTeX entry from 
http://citeseer.ist.psu.edu/monge00adaptive.html):

@misc{ monge-adaptive,
  author = "Alvaro E. Monge",
  title = "An Adaptive and Efficient Algorithm for Detecting 
Approximately Duplicate
Database Records",
  url = "citeseer.ist.psu.edu/monge00adaptive.html" }

There is a lot of literature--try a google search for "approximate 
string match"--but very little publically available code in this area, 
from what I could gather.  Removing punctuation, etc., as others have 
suggested in this thread, is _not_sufficient_.  Presumably you want to 
be able to match typos or phonetic errors as well.  This paper's 
algorithm deals with those problems quite nicely,

--

Aaron Bingham
Application Developer
Cenix BioScience GmbH

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Re: [ANN] iCalendar package 0.9

[Roger Binns]

"Max M" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED]
> http://www.mxm.dk/products/public/ical/
>
> Any feedback would be welcome.

How well do you cope with the crud that real programs generate?  Does it work
with the different dialects uses out there?  Can it at least identify them?

The reason why I ask is this would be useful for BitPim.  When I wrote the
code for doing vCards, I soon found that there wasn't actually a single
program out there on Windows, Linux or Mac that actually generated 100%
standards conformant vCards.  They generally complied with the spirit,
but screwed up character encoding, misspelled fields names, didn't do
the right thing when commas and semi-colons were present in values etc.
I assume the thing happens with ical.

Roger 


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Re: lambda

[Antoon Pardon]

Op 2005-01-17, Steve Holden schreef <[EMAIL PROTECTED]>:
> Antoon Pardon wrote:
>
> Mostly, though, I was trying to say that I found your nitpicking 
> insistence on terminological exactitude, even when giving advice to 
> those new to the language, both inappropriate and tedious in the extreme.

I think it is appropiate because not all new to the language are new to
programming and even newbees have a right to know how it really is.  Otherwise
after some time you get experienced users who don't know the fact. In
this case for example there are a number of people who flat out assert that
muatble dict keys in pyhthon is impossible.

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Re: lambda

[Steven Bethard]

Antoon Pardon wrote:
In this case for example there are a number of people who flat out
assert that muatble dict keys in pyhthon is impossible.
If you run into any of these folks, please point them to:
http://www.python.org/moin/DictionaryKeys
It's a pretty good summary of one of the more recent threads on this 
topic by Peter Maas and myself.  If you feel like your point is not 
covered[1], feel free to add some additional material.  (That is, after 
all, the point of a wiki.)

Steve
[1] I assume that you feel this way because you have repeated 
essentially the same point about 5 times in this thread.  The wiki is a 
chance to make your statement once, and then simply post a pointer once 
per appropriate thread.  It might save you some time...
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inbuilt function buffer()

[km]

Hi all,
I which context is the inbuilt function buffer() used ? 
regards,
KM
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Re: Advice to a Junior in High School?

[Stephen Waterbury]

collegebabe2004 wrote:
wow! Aren't we getting ahead of ourselves?  ...
Well I'm like "yuhhh!"  Like, you know, Japanese ...
oh I am *so* shur!
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Re: Integration with java

[Dan Bishop]

Istvan Albert wrote:
> Joachim Boomberschloss wrote:
>
> >  the code is already written in Python, using the
> >  standard libraries and several extension modules
>
> One thing to keep in mind is that Jython does not
> integrate CPython, instead it "understands" python code
> directly. So if you have a C extension that works with python
> it won't work with Jython.

Also, Jython is several versions behind CPython, so any Python code
that uses generators or new-style division won't work either.

> My feeling is that if you had a lot of Java code written and
> wanted to build on that with python Jython would be a better
> fit than vice versa.

I agree.

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Re: [Python-Dev] Getting rid of unbound methods: patch available

[Nick Coghlan]

Guido van Rossum wrote:
What do people think? (My main motivation for this, as stated before,
is that it adds complexity without much benefit.)
Something important that came up in my response to Marc-Andre:
What about C method implementations which are relying on this typecheck and 
assuming that 'self' is (nearly) guaranteed to be of the correct type?

The string object implementation is where I noticed this assumption being made, 
but I suspect it would be fairly widespread.

Obviously, use of im_func can break such code already, but that's a far cry from 
having C.f skip the type check.

Cheers,
Nick.
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Re: extension module, thread safety?

[Nick Coghlan]

Pierre Barbier de Reuille wrote:
With the current CPython, it's very hard to mix Python and C in a 
multithreading application (with C-threads, not Python-threads). In fact 
I never really succeeded in that task because of that GIL ! I have a 
multi-thread application but every bit of Python code must be run into a 
Python thread. To be more precise, I wanted to be able to call Python 
code in response to some GUI events, and I didn't want to instanciate a 
new interpreter for I wanted to be able to access the environment of my 
main Python interpreter.
I don't understand. This is what PyGILState_Ensure and PyGILState_Release are 
for - so C code can leave the GIL unlocked by default, and only grab it when 
they want to call into the C/Python API.

Regards,
Nick.
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Re: extension module, thread safety?

[Pierre Barbier de Reuille]

Nick Coghlan a écrit :
Pierre Barbier de Reuille wrote:
With the current CPython, it's very hard to mix Python and C in a 
multithreading application (with C-threads, not Python-threads). In 
fact I never really succeeded in that task because of that GIL ! I 
have a multi-thread application but every bit of Python code must be 
run into a Python thread. To be more precise, I wanted to be able to 
call Python code in response to some GUI events, and I didn't want to 
instanciate a new interpreter for I wanted to be able to access the 
environment of my main Python interpreter.

I don't understand. This is what PyGILState_Ensure and 
PyGILState_Release are for - so C code can leave the GIL unlocked by 
default, and only grab it when they want to call into the C/Python API.

Regards,
Nick.
Ok, I wondered why I didn't know these functions, but they are new to 
Python 2.4 ( and I didn't take the time to look closely at Python 2.4 as 
some modules I'm working with are still not available for Python 2.4). 
But if it really allows to call Python code outside a Python thread ... 
then I'll surely use that as soon as I can use Python 2.4 :) Thanks for 
the hint :)

Pierre
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Re: wxPython and PyGame - do they play well together?

[Erik Bethke]

Thank you,

My apologies to all for insufficient googling

-Erik

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Re: generator expressions: performance anomaly?

[Nick Coghlan]

Raymond Hettinger wrote:
[Delaney, Timothy C]
Nick's other suggestion - that genexps propagate __len__ - might
still be interesting. Of course, it would only be applicable for
unconditional genexps(i.e. no if clause).
Length transparency for iterators is not as general as one would expect.  I 
once
spent a good deal of effort exploring where it made sense, and I was surprised
to find that it only rarely works out.  Length transparency is an unexpectedly
thorny subject with many dead-ends which precludes a fully general solution such
as that proposed by Nick.
For a recap of my research, see the docstring for Lib/test/test_iterlen.py .
"""The situation slightly more involved whenever an object allows length 
mutation during iteration. """

Ouch. Nice understatement.
It's rather unfortunate that we can't make use of the length information even 
when the source *doesn't* mutate, though. I'll have to think some more to see if 
I can come up with any concrete ideas for you to shoot down :)

Cheers,
Nick.
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Re: Socket and Tkinter Problem

[Tonino]

hi,

was wondering if you ever got a reply ?
Did you mannage to sort this out ?

I am wanting todo the same thing - just have a window that connects to
a port and displays the data it receives from that port in the window?
Thanks
Tonino

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Re: extension module, thread safety?

[Nick Coghlan]

Pierre Barbier de Reuille wrote:
Ok, I wondered why I didn't know these functions, but they are new to 
Python 2.4 ( and I didn't take the time to look closely at Python 2.4 as 
some modules I'm working with are still not available for Python 2.4). 
But if it really allows to call Python code outside a Python thread ... 
then I'll surely use that as soon as I can use Python 2.4 :) Thanks for 
the hint :)
The Python 2.4 docs claim the functions were added in Python 2.3, even though 
they aren't documented in the 2.3.4 docs.

The 2.3 release PEP (PEP 283) confirms that PEP 311 (which added these 
functions) went in.

Cheers,
Nick.
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Re: [ANN] iCalendar package 0.9

[Max M]

Roger Binns wrote:
"Max M" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED]
http://www.mxm.dk/products/public/ical/
Any feedback would be welcome.

How well do you cope with the crud that real programs generate?  Does it work
with the different dialects uses out there?  Can it at least identify them?

It depends on how badly the data is screwed up. But generally it should 
be able to work on incorrect implementations.

It doesn't care of the spelling of property and parameter names. Though 
type conversions will need to be done slightly more manual.

If something like 'dtstart' is misspelled it will not return a datetime
>>> cal.decoded('datestart')
But if you know that it is misspelled you can get it, and convert it 
manually like:

>>> from PropertyValues import vDDDType
>>> vDDDType.from_ical(cal['datestart'])
--
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http://www.mxm.dk/
IT's Mad Science
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Re: ftplib strange behaviour

[siggy2]

Kartic wrote:
> I have used ftplib but never for such a huge file (assuming your
> problem is related to the size of the file).
we're doing that since python 2.2 from different site to different
hosts where our script was installed...
needless to say all the (few) problems we had came from the servers...

> Have you tried downloading the file using another ftp client? Does
that
> download succeed? The reason I ask is because I have attempted
> downloads from servers that terminate the connection after a certain
> connection time, in the middle of a download!
After two weeks the sysadms of the ftp server
discovered a misconficuration in some router... Anyway
we had already change the script: we  managed to trap any exception and

we added a "retry" loop.

>
> That is the best I can help you out with the information.
Thank you for your help anyway.

bye,
   PiErre

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Re: Problem parsing namespaces with xml.dom.minidom

[Mike McGavin]

Hi Fredrik.
Fredrik Lundh wrote:
I'm not terribly experienced with XML in general, so it's possible that I'm just incorrectly 
interpreting how things are supposed to work to begin with.  If this is the case, please accept my 
apologies, but I'd like any suggestions for how I should be doing it.  I'd really just like to be 
able to parse an XML document into a DOM, and then be able to pull out elements relative to their 
namespaces.

is the DOM API an absolute requirement?
It wouldn't need to conform to the official specifications of the DOM 
API, but I guess I'm after some comparable functionality.

In particular, I need to be able to parse a namespace-using XML document 
into some kind of node tree, and then being able to query the tree to 
select elements based on their namespace and local tag names, and so on. 
 I don't mind if the methods provided don't conform exactly to DOM 
specifications.

I guess I could write my own code to build a namespace-recognising DOM 
from an XML file, but it seems as if that's already been done and I'd be 
very surprised if it hadn't.  I just can't figure out why minidom 
doesn't seem to be working properly for me when namespaces are involved.

Thanks.
Mike.
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Re: Problem parsing namespaces with xml.dom.minidom

[Fredrik Lundh]

Mike McGavin wrote:

>> is the DOM API an absolute requirement?
>
> It wouldn't need to conform to the official specifications of the DOM API, 
> but I guess I'm after 
> some comparable functionality.
>
> In particular, I need to be able to parse a namespace-using XML document into 
> some kind of node 
> tree, and then being able to query the tree to select elements based on their 
> namespace and local 
> tag names, and so on. I don't mind if the methods provided don't conform 
> exactly to DOM 
> specifications.

sounds like this might be exactly what you need:

http://effbot.org/zone/element-index.htm

(it's also the fastest and most memory-efficient Python-only parser you
can get, but I suppose that's not a problem ;-)

 



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Re: generator expressions: performance anomaly?

[Antoon Pardon]

Op 2005-01-18, Nick Coghlan schreef <[EMAIL PROTECTED]>:
> Raymond Hettinger wrote:
>> [Delaney, Timothy C]
>> 
>>>Nick's other suggestion - that genexps propagate __len__ - might
>>>still be interesting. Of course, it would only be applicable for
>>>unconditional genexps(i.e. no if clause).
>> 
>> Length transparency for iterators is not as general as one would expect.  I 
>> once
>> spent a good deal of effort exploring where it made sense, and I was 
>> surprised
>> to find that it only rarely works out.  Length transparency is an 
>> unexpectedly
>> thorny subject with many dead-ends which precludes a fully general solution 
>> such
>> as that proposed by Nick.
>> 
>> For a recap of my research, see the docstring for Lib/test/test_iterlen.py .
>
> """The situation slightly more involved whenever an object allows length 
> mutation during iteration. """
>
> Ouch. Nice understatement.
>
> It's rather unfortunate that we can't make use of the length information even 
> when the source *doesn't* mutate, though. I'll have to think some more to see 
> if 
> I can come up with any concrete ideas for you to shoot down :)

Something else I was thinking about. I think it would be nice if the
python compilor could figure out whether a genexp in a list or tuple
expression always generates the same list or tuple and then instead
of generating code would generate the list or tuple in place.

-- 
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Re: Problem parsing namespaces with xml.dom.minidom

[Paul Prescod]

You've reversed some function parameters. Here's a program that works 
fine (note that you don't need to set up a SAX parser):

from xml.dom import minidom
text = '''

   alias
   Thu Jan 30 15:06:06 NZDT 2003
   
 Nothing
   

'''
# Parse the string into a minidom
mydom = minidom.parseString(text)
# Look for some elements
# This one shouldn't return any (I think).
object_el1 = mydom.getElementsByTagName("xte:object")
# This one definitely should, at least for what I want.
object_el2 = mydom.getElementsByTagNameNS(
'http://www.mcs.vuw.ac.nz/renata/xte',"object",
)
print '1: ' + str(object_el1)
print '2: ' + str(object_el2)
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Re: Fuzzy matching of postal addresses

[Simon Brunning]

You might find these at least periperally useful:



They refer to address formatting rather than de-duping - but
normalising soulds like a useful first step to me.

-- 
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Simon B,
[EMAIL PROTECTED],
http://www.brunningonline.net/simon/blog/
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Re: lambda

[Simon Brunning]

On 18 Jan 2005 07:51:00 GMT, Antoon Pardon <[EMAIL PROTECTED]> wrote:
> 3 mutating an item in a sorted list *does* *always* cause problems

No, it doesn't. It might cause the list no longer to be sorted, but
that might or might no be a problem.

> More specific the Decimal class is mutable and usable as dict key.

Decimal objects are immutable, so far as I know.

>>> from decimal import Decimal
>>> spam = Decimal('1.2')
>>> eggs = spam
>>> eggs is spam
True
>>> eggs += 1
>>> eggs is spam
False

-- 
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Simon B,
[EMAIL PROTECTED],
http://www.brunningonline.net/simon/blog/
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Re: lambda

[Antoon Pardon]

Op 2005-01-18, Simon Brunning schreef <[EMAIL PROTECTED]>:
> On 18 Jan 2005 07:51:00 GMT, Antoon Pardon <[EMAIL PROTECTED]> wrote:
>> 3 mutating an item in a sorted list *does* *always* cause problems
>
> No, it doesn't. It might cause the list no longer to be sorted, but
> that might or might no be a problem.

Than in the same vain I can say that mutating a key in a dictionary
doesn't always cause problems either. Sure it may probably make a
key unaccessible directly, but that might or might not be a problem.

>> More specific the Decimal class is mutable and usable as dict key.
>
> Decimal objects are immutable, so far as I know.
>
 from decimal import Decimal
 spam = Decimal('1.2')
 eggs = spam
 eggs is spam
> True
 eggs += 1
 eggs is spam
> False
>

>>> from decimal import Decimal
>>> spam = Decimal('1.2')
>>> egg = spam
>>> spam._int = (1, 3)
>>> spam
Decimal("1.3")
>>> spam is egg
True

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Re: generator expressions: performance anomaly?

[Steve Holden]

Antoon Pardon wrote:
Op 2005-01-18, Nick Coghlan schreef <[EMAIL PROTECTED]>:
Raymond Hettinger wrote:
[Delaney, Timothy C]

Nick's other suggestion - that genexps propagate __len__ - might
still be interesting. Of course, it would only be applicable for
unconditional genexps(i.e. no if clause).
Length transparency for iterators is not as general as one would expect.  I 
once
spent a good deal of effort exploring where it made sense, and I was surprised
to find that it only rarely works out.  Length transparency is an unexpectedly
thorny subject with many dead-ends which precludes a fully general solution such
as that proposed by Nick.
For a recap of my research, see the docstring for Lib/test/test_iterlen.py .
"""The situation slightly more involved whenever an object allows length 
mutation during iteration. """

Ouch. Nice understatement.
It's rather unfortunate that we can't make use of the length information even 
when the source *doesn't* mutate, though. I'll have to think some more to see if 
I can come up with any concrete ideas for you to shoot down :)

Something else I was thinking about. I think it would be nice if the
python compilor could figure out whether a genexp in a list or tuple
expression always generates the same list or tuple and then instead
of generating code would generate the list or tuple in place.
Since it doesn't yet optimize 2+5 to a constant-folded 7 you should 
realize that you are suggesting a large increase in the compiler's 
analytical powers.

I agree it would be nice under certain circumstances, but don't forget 
that unlike list comprehensions (for which it would be even nicer) the 
whole point of generator expressions is often to defer the generation of 
the individual items until they are required and thereby relieve stress 
on memory.

As an edge case to demonstrate the point, what about a constant but 
infinite sequence?

regards
 Steve
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Re: Central New Jersey PIG Meeting -- Python Interest Group In Princeton PIG/IP

[[EMAIL PROTECTED]]

Yes Jay. PIG/IP meetings are publicly open with no RSVP necessary.
Most of the folks coming are LUG/IP members, as I am and the location
is the same as LUG/IP meetings. We haven't formalized the group's
affiliation yet. 

-- Jon

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Re: Integration with java

[Steve Holden]

Dan Bishop wrote:
Istvan Albert wrote:
Joachim Boomberschloss wrote:

the code is already written in Python, using the
standard libraries and several extension modules
One thing to keep in mind is that Jython does not
integrate CPython, instead it "understands" python code
directly. So if you have a C extension that works with python
it won't work with Jython.

Also, Jython is several versions behind CPython, so any Python code
that uses generators or new-style division won't work either.

My feeling is that if you had a lot of Java code written and
wanted to build on that with python Jython would be a better
fit than vice versa.

I agree.
Also let's not forget that the PSF has funded a project that's intended 
to help Jython get up to the curve - see 
http://www.python.org/psf/grants/Jython_PSF_Grant_Proposal.pdf. If that 
project succeeds, and if 2.5 development *does* focus mostly on the 
library, there's a sporting chance that Jython can be fully up to date 
for the 2.5 release.

regards
 Steve
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Re: lambda

[Nick Coghlan]

Antoon Pardon wrote:
More specific the Decimal class is mutable and usable as dict key.
It's *meant* to be immutable though. The fact that we used __slots__ instead of 
__setattr__ to implement the immutability, so you *can* overwrite the slot 
variables if you really want to is merely an artifact of the current Python 
implementation.

The limited mutability bug will disappear in Python 2.5, so it's not a good 
example of a 'mutable' dict key (especially given that the only way to mutate it 
is to modify private variables directly).

And, as I've stated previously, if the issue of sane mutable keys in 
dictionaries and sets really bugs you so much - implement identity_dict and 
identity_set in C and lobby for their inclusion in the collections module.

On the more general point of "don't use mutable objects with non-identity based 
comparisons as dictionary keys", try teaching students for a while (or listen to 
those who have):

When stating useful general principles, it is never, ever worth it to get into 
the quibbly little details about exceptions to the principle. If students ask, 
admit that they exist, but point out that the exceptions are rare, and not worth 
worrying about at that point in their learning.

Only when one is aware of the reasons for a principle, can one be aware of good 
reasons not to follow it :)

Cheers,
Nick.
--
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---
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Re: generator expressions: performance anomaly?

[Diez B. Roggisch]

> Something else I was thinking about. I think it would be nice if the
> python compilor could figure out whether a genexp in a list or tuple
> expression always generates the same list or tuple and then instead
> of generating code would generate the list or tuple in place.

This won't ever happen in python - at least not in python otherwise similar
to the one we know...

The thing you're after is known as "common subexpression elemination" and
can only be done in purely functional languages. While that certainly is an
interesting property of a language, it e.g. forbids functions like
time.time() - a too huge paradigm shift for python.

-- 
Regards,

Diez B. Roggisch
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Re: generator expressions: performance anomaly?

[Antoon Pardon]

Op 2005-01-18, Steve Holden schreef <[EMAIL PROTECTED]>:
> Antoon Pardon wrote:
>
>> Op 2005-01-18, Nick Coghlan schreef <[EMAIL PROTECTED]>:
>> 
>>>Raymond Hettinger wrote:
>>>
[Delaney, Timothy C]


>Nick's other suggestion - that genexps propagate __len__ - might
>still be interesting. Of course, it would only be applicable for
>unconditional genexps(i.e. no if clause).

Length transparency for iterators is not as general as one would expect.  I 
once
spent a good deal of effort exploring where it made sense, and I was 
surprised
to find that it only rarely works out.  Length transparency is an 
unexpectedly
thorny subject with many dead-ends which precludes a fully general solution 
such
as that proposed by Nick.

For a recap of my research, see the docstring for Lib/test/test_iterlen.py .
>>>
>>>"""The situation slightly more involved whenever an object allows length 
>>>mutation during iteration. """
>>>
>>>Ouch. Nice understatement.
>>>
>>>It's rather unfortunate that we can't make use of the length information 
>>>even 
>>>when the source *doesn't* mutate, though. I'll have to think some more to 
>>>see if 
>>>I can come up with any concrete ideas for you to shoot down :)
>> 
>> 
>> Something else I was thinking about. I think it would be nice if the
>> python compilor could figure out whether a genexp in a list or tuple
>> expression always generates the same list or tuple and then instead
>> of generating code would generate the list or tuple in place.
>> 
> Since it doesn't yet optimize 2+5 to a constant-folded 7 you should 
> realize that you are suggesting a large increase in the compiler's 
> analytical powers.

Well I can dream, cant I?

> I agree it would be nice under certain circumstances, but don't forget 
> that unlike list comprehensions (for which it would be even nicer) the 
> whole point of generator expressions is often to defer the generation of 
> the individual items until they are required and thereby relieve stress 
> on memory.
>
> As an edge case to demonstrate the point, what about a constant but 
> infinite sequence?

Maybe I was not clear enough. I meant to limit it to cases such as

   lst = list(genexp)
   tpl = tuple(genexp)


Since in such cases the object is build in memory any way, I don't
think it would be a problem of having them prebuilt in memory, or am
I missing something?

-- 
Antoon Pardon
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Re: List problems in C code ported to Python

[Bengt Richter]

On Mon, 17 Jan 2005 15:28:56 GMT, Lucas Raab <[EMAIL PROTECTED]> wrote:

>Lucas Raab wrote:
>> I'm done porting the C code, but now when running the script I 
>> continually run into problems with lists. I tried appending and 
>> extending the lists, but with no avail. Any help is much appreciated 
>> Please see both the Python and C code at 
>> http://home.earthlink.net/~lvraab. The two files are ENIGMA.C and engima.py
>> 
>> TIA
>
>OK, here's the Python code and the corresponding C code:
>
>def init_mach():
>   import string
>   #setup rotor data
>   i=1
>   j=0
>   for j in j<26, j+1:
I urge you to explore interactively. And do it line by line
(and even expression by expression when you get mystifying results) until you
are more familiar with the language.

E.g., what do you think the values of j will be here?
 >>> j=0
 >>> for j in j<26, j+1: print j,
 ...
 True 1

Surprised?

 >>> j<26, j+1
 (True, 2)

Hm, surprised at the 2 here?

 >>> j=0
 >>> j<26, j+1
 (True, 1)

IOW, your 'for' line was equivalent to iterating through a length-2 tuple
   for j in (True, 1):  # since if j is 0, j<26 is True, and j+1 is 1
What you probably wanted was j starting with 0 and ending with 25, which you 
get by

 >>> for j in xrange(26): print j,
 ...
 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

(The comma at the end of the print statement is to get a space before
 the next output instead of a newline).
   
>   data[4],[j] = (ref_rotor[j] - 'A'+26) % 26
Had you tried an interactive experiment, you would have had some real questions 
to ask ;-)

 >>> j=0
 >>> for j in xrange(26):
 ... data[4],[j] = (ref_rotor[j] - 'A'+26) % 26
 ...
 Traceback (most recent call last):
   File "", line 2, in ?
 NameError: name 'ref_rotor' is not defined

Ok, fix that with something
 >>> ref_rotor = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'  # something legal
 >>> j=0
 >>> for j in xrange(26):
 ... data[4],[j] = (ref_rotor[j] - 'A'+26) % 26
 ...
 Traceback (most recent call last):
   File "", line 2, in ?
 TypeError: unsupported operand type(s) for -: 'str' and 'str'

You might have had to ask at this point what that meant, but you could get 
closer by
trying the expressions and their terms:

 >>> (ref_rotor[j] - 'A'+26) % 26
 Traceback (most recent call last):
   File "", line 1, in ?
 TypeError: unsupported operand type(s) for -: 'str' and 'str'

Pare it down

 >>> (ref_rotor[j] - 'A'+26)
 Traceback (most recent call last):
   File "", line 1, in ?
 TypeError: unsupported operand type(s) for -: 'str' and 'str'

Check pieces
 >>> j
 0
 >>> ref_rotor[j]
 'A'

Substitute to make painfully clear

 >>> ('A' - 'A'+26)
 Traceback (most recent call last):
   File "", line 1, in ?
 TypeError: unsupported operand type(s) for -: 'str' and 'str'
 >>> ('A' - 'A')
 Traceback (most recent call last):
   File "", line 1, in ?
 TypeError: unsupported operand type(s) for -: 'str' and 'str'

What is 'A' ?
 >>> type('A')
 

Hm, characters are strings, not char types that are directly type compatible
with int. It takes a conversion. To get from single-char string to its integer 
code
and back:

 >>> ord('A')
 65
 >>> chr(65)
 'A'

Another experiment:

 >>> ord('AB')
 Traceback (most recent call last):
   File "", line 1, in ?
 TypeError: ord() expected a character, but string of length 2 found


Now you are in a position to use ord, and get a little further:

 >>> j=0
 >>> for j in xrange(26):
 ... data[4],[j] = (ord(ref_rotor[j]) - ord('A')+26) % 26
 ...
 Traceback (most recent call last):
   File "", line 2, in ?
 TypeError: unpack non-sequence

Was the right hand side a problem?
 >>> j
 0
 >>> (ord(ref_rotor[j]) - ord('A')+26) % 26
 0

Apparently not, so what it was trying to do was

 >>> data[4],[j] = 0
 Traceback (most recent call last):
   File "", line 1, in ?
 TypeError: unpack non-sequence

What was it trying to unpack? And why?
Well, you might have known if you had been through the tutorial, but at least
you would have had a specific question about a specific error at this point.

Note:
 >>> a, b = 0
 Traceback (most recent call last):
   File "", line 1, in ?
 TypeError: unpack non-sequence

I.e., when you have commas (or even one) on the left hand side of an assignment,
that is asking python to unpack a sequence on the right hand side and assign to
corresponding items on the left. So e.g.,

 >>> a, b = 0, 1
will unpack the tuple formed by 0, 1
 >>> a
 0
 >>> b
 1
You can unpack any sequence of the same length, and strings happen to be 
sequences:

 >>> a,b = 'XY'
 >>> a
 'X'
 >>> b
 'Y'

Ok, enough of that. The comma was obviously a problem so, try it without:


 >>> data[4][j] = 0
 Traceback (most recent call last):
   File "", line 1, in ?
 NameError: name 'data' is not defined

I could go on, but IMO if you expect help, you should do your part, and at least
post code that you have tried and which compiles or runs up to the point where
it shows an error that you need help with.

And 

Re: generator expressions: performance anomaly?

[Ola Natvig]

Antoon Pardon wrote:
Op 2005-01-18, Steve Holden schreef <[EMAIL PROTECTED]>:
Antoon Pardon wrote:

Op 2005-01-18, Nick Coghlan schreef <[EMAIL PROTECTED]>:

Raymond Hettinger wrote:

[Delaney, Timothy C]

Nick's other suggestion - that genexps propagate __len__ - might
still be interesting. Of course, it would only be applicable for
unconditional genexps(i.e. no if clause).
Length transparency for iterators is not as general as one would expect.  I 
once
spent a good deal of effort exploring where it made sense, and I was surprised
to find that it only rarely works out.  Length transparency is an unexpectedly
thorny subject with many dead-ends which precludes a fully general solution such
as that proposed by Nick.
For a recap of my research, see the docstring for Lib/test/test_iterlen.py .
"""The situation slightly more involved whenever an object allows length 
mutation during iteration. """

Ouch. Nice understatement.
It's rather unfortunate that we can't make use of the length information even 
when the source *doesn't* mutate, though. I'll have to think some more to see if 
I can come up with any concrete ideas for you to shoot down :)

Something else I was thinking about. I think it would be nice if the
python compilor could figure out whether a genexp in a list or tuple
expression always generates the same list or tuple and then instead
of generating code would generate the list or tuple in place.
Since it doesn't yet optimize 2+5 to a constant-folded 7 you should 
realize that you are suggesting a large increase in the compiler's 
analytical powers.

Well I can dream, cant I?

I agree it would be nice under certain circumstances, but don't forget 
that unlike list comprehensions (for which it would be even nicer) the 
whole point of generator expressions is often to defer the generation of 
the individual items until they are required and thereby relieve stress 
on memory.

As an edge case to demonstrate the point, what about a constant but 
infinite sequence?

Maybe I was not clear enough. I meant to limit it to cases such as
   lst = list(genexp)
   tpl = tuple(genexp)
Since in such cases the object is build in memory any way, I don't
think it would be a problem of having them prebuilt in memory, or am
I missing something?
Perhaps it had been better if that kind of functionality were 
implemented with a different syntax, I don't know enough about how the 
python interpreter works but perhaps it should be possible to execute 
some expressions with genexp syntax when compiling to bytecode. That 
should be a quite trivial extension.

examples using '<' list-comp/genexp syntax '>':
lst = 
or perhaps
lst = list()
Would result in the same bytecode as this expression
lst = [0, 1, 2, 3, ..., 98, 99]
It could be called static list comprehensions. But if it is a usefull 
extension is another dicussion.

ola
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Re: how to find site-packages path (Michael Hoffman) - use distutils

[Philippe C. Martin]

>> Why would you want to copy any *.pyc instead of compiling them on
site?



I know that sounds terrible to the open source community, but I do not
intend to release the source code for my product - pls go to
philippecmartin.com/applications.html for my _small_ contributions :-))

Regards,

Philippe



-- 
***
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SnakeCard LLC
www.snakecard.com
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Re: generator expressions: performance anomaly?

[Diez B. Roggisch]

>lst = list(genexp)
>tpl = tuple(genexp)
> 
> 
> Since in such cases the object is build in memory any way, I don't
> think it would be a problem of having them prebuilt in memory, or am
> I missing something?

Yes. Consider this:

lst = list(time.time() for i in xrange(10))
tpl = tuple(time.time() for i in xrange(10))


-- 
Regards,

Diez B. Roggisch
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Re: news feed problem -- anyone else?

[Bengt Richter]

On 17 Jan 2005 16:48:24 EST, Tim Daneliuk <[EMAIL PROTECTED]> wrote:

>Bengt Richter wrote:
>
>> I can see postings on google, but my news service
>> is having a problem since sometime during the weekend.
>> Can get old stuff from other n.g., but no new.
>> Wondering whether I'll see this via google.
>> 
>> Regards,
>> Bengt Richter
>
>Bengt -
>
>I've had very good luck using the following *free* newsfeed:
>
> http://individual.net/
>
>
>HTH,
Thanks,
I can see this via normal news now. But that looks good.

Regards,
Bengt Richter
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Re: generator expressions: performance anomaly?

[Ola Natvig]

Diez B. Roggisch wrote:
  lst = list(genexp)
  tpl = tuple(genexp)
Since in such cases the object is build in memory any way, I don't
think it would be a problem of having them prebuilt in memory, or am
I missing something?

Yes. Consider this:
lst = list(time.time() for i in xrange(10))
tpl = tuple(time.time() for i in xrange(10))


Would it be a bad solution to make that a list or tuple of ten 
time.time() calls, you could also restrict what theese prebuilding 
sequenses could contain, or perhaps try to prebuild them, and then fail 
if it's impossible.

--
--
 Ola Natvig <[EMAIL PROTECTED]>
 infoSense AS / development
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[wxpython] exclude files in a wx.FileDialog?

[John Field]

Hello, 

Is it possible to exclude certain files in a wx.FileDialog, so that the user 
won't see them and can't select them with the mouse in de File open window?

I was thinking of somehow extending the class FileDialog(Dialog) 
in the wx module _windows.py to a subclass, but I'm not sure how to do that 
(if feasible). 


cheers
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Re: extension module, thread safety?

[Pierre Barbier de Reuille]

Nick Coghlan a écrit :
The Python 2.4 docs claim the functions were added in Python 2.3, even 
though they aren't documented in the 2.3.4 docs.

The 2.3 release PEP (PEP 283) confirms that PEP 311 (which added these 
functions) went in.
Indeed, I just tested it and now it works fine :) Thanks a lot :)
Cheers,
Nick.
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Re: generator expressions: performance anomaly?

[Diez B. Roggisch]

> Would it be a bad solution to make that a list or tuple of ten
> time.time() calls, you could also restrict what theese prebuilding
> sequenses could contain, or perhaps try to prebuild them, and then fail
> if it's impossible.

I don't fully understand what you mean. Restricting them would mean to add
static declarations that say "I return the same whenever you call me" -
which is even more than the already fragile "const"  declaration of c++
allows. 

And for your second suggestion - how exactly do you check for failing?
Generating 2 elements and checking if they are equal to the first two of
the old list? What about overloaded __cmp__/__eq__, or just the last
element differing?

This problem is too complex to solve automatically - domain knowledge is
needed. As the code Antoon presented also suggests the simple solution:


lst = list(time.time() for i in xrange(10))
tpl = tuple(lst)


I don't see why this is a desirable feature at all. Keep in mind that
putting statements or even stackframes between those two statements above
utterly complicates things. And we even didn't dig into the dynamic
features of python that for example make it possible to alter time.time
like this

time.time = random.random()

so that it behaves totally different - while the syntactically equivalence
still holds. No chance of catching that. 
-- 
Regards,

Diez B. Roggisch
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Re: lambda

[Antoon Pardon]

Op 2005-01-18, Nick Coghlan schreef <[EMAIL PROTECTED]>:
> Antoon Pardon wrote:
>> More specific the Decimal class is mutable and usable as dict key.
>
> It's *meant* to be immutable though. The fact that we used __slots__ instead 
> of 
> __setattr__ to implement the immutability, so you *can* overwrite the slot 
> variables if you really want to is merely an artifact of the current Python 
> implementation.
>
> The limited mutability bug will disappear in Python 2.5, so it's not a good 
> example of a 'mutable' dict key (especially given that the only way to mutate 
> it 
> is to modify private variables directly).
>
> And, as I've stated previously, if the issue of sane mutable keys in 
> dictionaries and sets really bugs you so much - implement identity_dict and 
> identity_set in C and lobby for their inclusion in the collections module.

I'm not bugged by its absence in Python. I'm bugged by the attitude
about them. But anyway I'm thinking about implementing a safe dictionary
that will copy whenever it would otherwise allow the risk of mutating a
key.

> On the more general point of "don't use mutable objects with non-identity 
> based 
> comparisons as dictionary keys", try teaching students for a while (or listen 
> to 
> those who have):

What kind of students?

I have implemented a hash table when I was a student and its
implementation allowed the use of 'mutable' objects as a key
without a problem. It simply always made copies when appropiate
and didn't allow external access to the keys. So although the
key objects were 'mutable' there was no way a user could accidently
mutate a key.

So don't use a mutable as a dictionary key isn't so much a dictionary
limitation in general but a specific limitation of the python implementation.

And yes I understand, the current implenatation is the result of the
fact that the same dictionaries are used internally for variables in
scopes and attributes in objects and the fact that no copies are
involved gives a boost to performance. But it could be argued that
providing these same dictionaries with those semantics to the users
was a premature optimisation.

> When stating useful general principles, it is never, ever worth it to get 
> into 
> the quibbly little details about exceptions to the principle. If students 
> ask, 
> admit that they exist, but point out that the exceptions are rare, and not 
> worth 
> worrying about at that point in their learning.

But don't use mutable keys is not a general principle. It is a principle
introduced by the limitations of the python implementations.

I don't like it when a good rule of thumb because of implementation
limitations is sold as a general principle.

-- 
Antoon Pardon
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Re: [perl-python] 20050118 keyed list

[Jay Tilton]

"Xah Lee" <[EMAIL PROTECTED]> wrote:

: # the syntax of keyed list in Perl is too complex
: # to be covered in a short message.

You've got to be joking.  You couldn't even muster enough skill to provide
Perl equivalents for the four simple Python statements you showed?

: # see "perldoc perldata" for an unix-styled course.

It's good to see your opinion on the _fantastic incompetent writting_[1] of
Perl's documentation has changed enough that you can recommend it to
novices.

[1]Message-ID: <[EMAIL PROTECTED]>

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Re: strange note in fcntl docs

[John Lenton]

On Mon, Jan 17, 2005 at 09:54:46PM -0600, Skip Montanaro wrote:
> 
> John> And, even if they were, the note is *still* wrong and misleading:
> John> fcntl is available on Windows, and os.open's flags won't be.
> 
> Does this read better?
> 
> [snip]

yes, and it takes me back to considering why file objects don't have
methods suck as lock, stat and mmap where those calls are available
through other mechanisms...

-- 
John Lenton ([EMAIL PROTECTED]) -- Random fortune:
Yo mando a mi gato y mi gato manda a su rabo. 


signature.asc
Description: Digital signature
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Re: Employablity of python programmers

[Premshree Pillai]

Hi,

I program in Python -- but not at work. There are very few
opportunities for Python work in India. As of now, at least. (If
somebody else has better information, please correct me.)

A lot of people _do_ use Python, but not many organizations use it.

Okay, as an aside, as a computer _science_ graduate, a programming
language alone should not decide what career you choose. Nor should
you choose a career based on the liking of a particular language
alone.

And I kinda don't understand this idea of "choosing what's best". How
do you define "what is best"? I guess you should do what you like --
and not something that is "in demand".

My 2 paisas. :)

On 17 Jan 2005 07:09:09 -0800, Mir Nazim <[EMAIL PROTECTED]> wrote:
> Hi,
> 
> Here I am once again to give a bit trouble.
> 
> I am at the verge of completing my graduation in computer sciences. I
> will be graduating within 6-8 months. Now I am faced with the problems
> of my career. I am in a fix what skill set I must choose to be safe as
> far as job openings are concerned. I understand that skill set should
> be that one like most but job is also important. I will try to achieve
> a balance in both with the help of you advice.
> 
> I am currently developing in PHP as a freelance web developer. But I
> want to move to python(for all it all cool reasons discussed a zillion
> times on c.l.py) and wanted to know the job oportunites available to a
> python programmer(I know these have been also discussed a zillion time
> here but still..). I am living in India and would like to know about
> employability of python programmers in India (I know that a few Indians
> frequent c.l.py. Hello Sridhar, where are you).
> 
> I would also like to know that if the knowledge of any other language
> will boost employability of a python programmer. As far as I see it,
> the following combination are desirable.
> 
> 1) C/C++ and Python.
> 2) Java and Python.
> 3) Pure Python.
> 
> Out of the three Java along with python seems to be straight forward
> choice as far as employability is concerned. But I would like to know
> the benifits which one is a better career choice to take out of these
> three choices(other suggestions are welcome). For me choice three would
> be better, not because I have only one language to learn. If I choose
> choice three I could spend more time in learning different approaches
> to develop the application and better master the library and frameworks
> avaialble for python.
> 
> So what are the recomendations from your side. Please help.
> Thanks
> ---
> Mir Nazim.
> 
> --
> http://mail.python.org/mailman/listinfo/python-list
> 


-- 
Premshree Pillai
http://www.livejournal.com/~premshree
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Re: [wxpython] exclude files in a wx.FileDialog?

[Franz Steinhaeusler]

On 18 Jan 2005 13:23:24 GMT, John Field <[EMAIL PROTECTED]> wrote:

>Hello, 
>
>Is it possible to exclude certain files in a wx.FileDialog, so that the user 
>won't see them and can't select them with the mouse in de File open window?
>
>I was thinking of somehow extending the class FileDialog(Dialog) 
>in the wx module _windows.py to a subclass, but I'm not sure how to do that 
>(if feasible). 
>
>
>cheers

wx.FileDialog is only a wrapper for the api FileDialog (at least this 
applies for windows) and therefore it is not possible to derive from it.

Really exclude, I think, is not possible.

You can put a mask 
wx.FileDialog(...wildcard = "BMP files (*.bmp)|*.bmp|GIF files
(*.gif)|*.gif")

Otherwise you have to create your own FileDialog.
-- 
Franz Steinhaeusler
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Re: generator expressions: performance anomaly?

[Stephen Thorne]

On Tue, 18 Jan 2005 07:12:18 -0500, Steve Holden <[EMAIL PROTECTED]> wrote:
> Since it doesn't yet optimize 2+5 to a constant-folded 7 you should
> realize that you are suggesting a large increase in the compiler's
> analytical powers.

As in interesting aside to this, you might be interested to know that
PHP has constant folding, allowing you to do things like
$foo = 7+9; and have it generate bytecode that is "let 'foo' equal 16"
or somesuch.

PHP achieves this by having a subset of expression parsing available
only for situations where a folded constant is allowed.

i.e.
class Foo {
  var $bar = 1+4; /* this constant is folded */
}

static_scalar: /* compile-time evaluated scalars */
common_scalar |   T_STRING |   '+' static_scalar |
  '-' static_scalar |   T_ARRAY '(' static_array_pair_list ')'
;
common_scalar:
/* all numbers, strings-not-containing-variable-interpolation and a
few hacks like __FILE__ and __LINE__ */
;

As you can see from the grammar, there are any number of ways this can break.

i.e.
Parse Error, * isn't allowed:
class Foo { var $bar = 60*60*24; }

Parse Error, neither is anything except + and -:
class Foo { var $bar = 256 & 18; }

Parse Error, and definately not variables:
$baz = 12;
class Foo { var $bar = $baz*2; }

I compute 60*60*24 every time around the loop:
foreach ($myarray as $value) { $x = 60*60*24*$value; }

Thankful, Former PHP Programmer,
Stephen Thorne.
-- 
http://mail.python.org/mailman/listinfo/python-list

Re: generator expressions: performance anomaly?

[Ola Natvig]

Diez B. Roggisch wrote:
Would it be a bad solution to make that a list or tuple of ten
time.time() calls, you could also restrict what theese prebuilding
sequenses could contain, or perhaps try to prebuild them, and then fail
if it's impossible.

I don't fully understand what you mean. Restricting them would mean to add
static declarations that say "I return the same whenever you call me" -
which is even more than the already fragile "const"  declaration of c++
allows. 

And for your second suggestion - how exactly do you check for failing?
Generating 2 elements and checking if they are equal to the first two of
the old list? What about overloaded __cmp__/__eq__, or just the last
element differing?
This problem is too complex to solve automatically - domain knowledge is
needed. As the code Antoon presented also suggests the simple solution:
lst = list(time.time() for i in xrange(10))
tpl = tuple(lst)
I don't see why this is a desirable feature at all. Keep in mind that
putting statements or even stackframes between those two statements above
utterly complicates things. And we even didn't dig into the dynamic
features of python that for example make it possible to alter time.time
like this
time.time = random.random()
so that it behaves totally different - while the syntactically equivalence
still holds. No chance of catching that. 
My thoughts where to let the 'leftmost' section of the expression to be 
intact so that any of the dynamic things done to this part, i.e. 
replacing time.time with random.random are taken into consideration. 
What can be done is to extract the expression into a loopless structure

lst = list(time.time() for i in xrange(10))
would be compiled to the bytecode version of:
lst = [time.time(), time.time(), time.time(), time.time() ...]
Then time.time can do whatever it wants to. It's the (x)range function 
that we need to enshure returns the same values in every execution. This 
*IS* a useless feature, but I think it's possible to make it work.

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

Re: generator expressions: performance anomaly?

[Diez B. Roggisch]

> My thoughts where to let the 'leftmost' section of the expression to be
> intact so that any of the dynamic things done to this part, i.e.
> replacing time.time with random.random are taken into consideration.
> What can be done is to extract the expression into a loopless structure
> 
> lst = list(time.time() for i in xrange(10))
> would be compiled to the bytecode version of:
> lst = [time.time(), time.time(), time.time(), time.time() ...]
> 
> Then time.time can do whatever it wants to. It's the (x)range function
> that we need to enshure returns the same values in every execution. This
> *IS* a useless feature, but I think it's possible to make it work.

What makes the leftmost expression different from the iterable returning
expression inside the for? The same arguments apply there.

-- 
Regards,

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

Re: generator expressions: performance anomaly?

[Antoon Pardon]

Op 2005-01-18, Diez B. Roggisch schreef <[EMAIL PROTECTED]>:
>> Something else I was thinking about. I think it would be nice if the
>> python compilor could figure out whether a genexp in a list or tuple
>> expression always generates the same list or tuple and then instead
>> of generating code would generate the list or tuple in place.
>
> This won't ever happen in python - at least not in python otherwise similar
> to the one we know...
>
> The thing you're after is known as "common subexpression elemination" and
> can only be done in purely functional languages. While that certainly is an
> interesting property of a language, it e.g. forbids functions like
> time.time() - a too huge paradigm shift for python.
>

I don't see how generating byte code for a = 9; when seeing the
expression a = 3 + 6, would be a problem for non-functional
languages.

I agree that things like [time.time() for i in xrange(10)] shouldn't
be pregenerated and that the problem is more complicated as I thought.

But during compilation the compilor could do an anlysis of the code
do determine whether there are side effects or not. If the compilor
then would store a code in the byte code for functions that are
guaranteed side-effect free and only pregenerated objects generated
by expressions with no side-effect, some common subexpression
elimination could be done even in a non-functional language.

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

MemoryError with parser.suite and wrong encoding declaration

[Sylvain Thenault]

Hi there !
I've noticed the following problem with python >= 2.3 (actually 2.3.4 and
2.4):

[EMAIL PROTECTED]:test$ python
Python 2.3.4 (#2, Sep 24 2004, 08:39:09)
[GCC 3.3.4 (Debian 1:3.3.4-12)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import parser
>>> parser.suite('# -*- coding: IBO-8859-1 -*-')
Traceback (most recent call last):
  File "", line 1, in ?
MemoryError
>>> parser.suite('# -*- coding: ISO-8859-1 -*-')


Shouldn't parser.suite just ignore the wrong encoding declaration, or at
least raise a more appropriate exception. IMHO the first solution
would be better, since that's the behaviour of the (C) python interpreter.

-- 
Sylvain Thénault   LOGILAB, Paris (France).

http://www.logilab.com   http://www.logilab.fr  http://www.logilab.org


-- 
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Re: generator expressions: performance anomaly?

[Ola Natvig]

What makes the leftmost expression different from the iterable returning
expression inside the for? The same arguments apply there.
It's not different, but it's a requirement that the iterable returns the 
same data every time. I know that anyone can type range = fancyRange and 
make this return a random number of random items.

But if that happens the expression cannot be transformed into a static 
list / tuple. Thats obvious.
--
http://mail.python.org/mailman/listinfo/python-list

Re: lambda

[John Lenton]

On Mon, Jan 17, 2005 at 03:20:01PM +, Antoon Pardon wrote:
> Op 2005-01-17, John Lenton schreef <[EMAIL PROTECTED]>:
> >
> > knowledgeable and experienced users know when to ignore the rules.
> 
> Then why seems there to be so few acknowledgement that these rules
> may indeed be broken by users. My experience is that anyone who suggests
> so runs the risk of being branded a (python) heretic.

First you learn the basics, then you think you're knowledgeable and
experienced, then you learn the rules, then you become one with the
rules, and then you may break them.

Most people suggesting these things haven't gotten past step #3. Using
Craig's parallel to C's goto, every and all newbie using gotos should
be lambasted: even if the use might be correct for the problem they
are trying to solve, the reasons for its correctness are far too
complex for them to grasp. But really, in practically any system, the
rules are generalizations, and they exist because the particulars are
too delicate to trust the unexperienced. The small print is
unprintable.

He dicho.

-- 
John Lenton ([EMAIL PROTECTED]) -- Random fortune:
Yo siempre seré el futuro Nobel. Debe ser una tradición escandinava.
-- Jorge Luis Borges. (1899-1986) Escritor argentino. 


signature.asc
Description: Digital signature
-- 
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Re: lambda

[Steve Holden]

Antoon Pardon wrote:
Op 2005-01-18, Nick Coghlan schreef <[EMAIL PROTECTED]>:
[...]
But don't use mutable keys is not a general principle. It is a principle
introduced by the limitations of the python implementations.
Sorry, but it *is* a general principle, adduced from the potential 
pitfalls available to inexperienced programmers when breaking the principle.

I don't like it when a good rule of thumb because of implementation
limitations is sold as a general principle.
So, since you are so good at nit-picking, perhaps you will explain the 
difference between "rule of thumb" and "general principle".

preferably-in-less-than-three-thousand-words-ly y'rs  - steve
--
Steve Holden   http://www.holdenweb.com/
Python Web Programming  http://pydish.holdenweb.com/
Holden Web LLC  +1 703 861 4237  +1 800 494 3119
--
http://mail.python.org/mailman/listinfo/python-list

Re: generator expressions: performance anomaly?

[Steve Holden]

Stephen Thorne wrote:
On Tue, 18 Jan 2005 07:12:18 -0500, Steve Holden <[EMAIL PROTECTED]> wrote:
Since it doesn't yet optimize 2+5 to a constant-folded 7 you should
realize that you are suggesting a large increase in the compiler's
analytical powers.

As in interesting aside to this, you might be interested to know that
PHP has constant folding, allowing you to do things like
$foo = 7+9; and have it generate bytecode that is "let 'foo' equal 16"
or somesuch.
PHP achieves this by having a subset of expression parsing available
only for situations where a folded constant is allowed.
i.e.
class Foo {
  var $bar = 1+4; /* this constant is folded */
}
static_scalar: /* compile-time evaluated scalars */
common_scalar |   T_STRING |   '+' static_scalar |
  '-' static_scalar |   T_ARRAY '(' static_array_pair_list ')'
;
common_scalar:
/* all numbers, strings-not-containing-variable-interpolation and a
few hacks like __FILE__ and __LINE__ */
;
As you can see from the grammar, there are any number of ways this can break.
i.e.
Parse Error, * isn't allowed:
class Foo { var $bar = 60*60*24; }
Parse Error, neither is anything except + and -:
class Foo { var $bar = 256 & 18; }
Parse Error, and definately not variables:
$baz = 12;
class Foo { var $bar = $baz*2; }
I compute 60*60*24 every time around the loop:
foreach ($myarray as $value) { $x = 60*60*24*$value; }
Thankful, Former PHP Programmer,
Stephen Thorne.
Yes, well, this just goes to confirm my belief that PHP isn't a 
programming language. I am always amazed at what's been achieved with it 
(though I sometimes wonder at what cost).

You probably already know that sensible compiled language systems have 
used constant folding since time immemorial, but Python has always 
eschewed it. That's what comes of being a pragmatist's language: if such 
optimizations really are required the programmer is expected to perform 
them.

and-ninety-nine-point-nine-nine-percent-of-the-time-they-aren't-ly y'rs 
 - steve
--
Steve Holden   http://www.holdenweb.com/
Python Web Programming  http://pydish.holdenweb.com/
Holden Web LLC  +1 703 861 4237  +1 800 494 3119

--
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Re: generator expressions: performance anomaly?

[Diez B. Roggisch]

> I don't see how generating byte code for a = 9; when seeing the
> expression a = 3 + 6, would be a problem for non-functional
> languages.

Most probably. But I don't see much code of that type that it would be worth
optimizing for, either. The cost for re-evaluation such an expression
doesn't really account for any performance problems you hit - in python, of
course.
See this:

[EMAIL PROTECTED]:/usr/lib/python2.3$ python timeit.py -c "[4*5 for i in
xrange(1)]"
100 loops, best of 3: 5.5e+03 usec per loop
[EMAIL PROTECTED]:/usr/lib/python2.3$ python timeit.py -c "[20 for i in
xrange(1)]"
100 loops, best of 3: 4.3e+03 usec per loop


Now of course the longer the expressions get, the more time it costs - but
how many long arithmetical expression of constant evaluation value do you
have?

> 
> I agree that things like [time.time() for i in xrange(10)] shouldn't
> be pregenerated and that the problem is more complicated as I thought.
> 
> But during compilation the compilor could do an anlysis of the code
> do determine whether there are side effects or not. If the compilor
> then would store a code in the byte code for functions that are
> guaranteed side-effect free and only pregenerated objects generated
> by expressions with no side-effect, some common subexpression
> elimination could be done even in a non-functional language.

This analysis would only be possible for the most primitive of examples, 
the reason beeing that due to the dynamic features syntactically equivalent
expressions can have totally different semantics. So its not really worth
the effort.

-- 
Regards,

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

Re: generator expressions: performance anomaly?

[Steve Holden]

Antoon Pardon wrote:
Op 2005-01-18, Diez B. Roggisch schreef <[EMAIL PROTECTED]>:
Something else I was thinking about. I think it would be nice if the
python compilor could figure out whether a genexp in a list or tuple
expression always generates the same list or tuple and then instead
of generating code would generate the list or tuple in place.
This won't ever happen in python - at least not in python otherwise similar
to the one we know...
The thing you're after is known as "common subexpression elemination" and
can only be done in purely functional languages. While that certainly is an
interesting property of a language, it e.g. forbids functions like
time.time() - a too huge paradigm shift for python.

I don't see how generating byte code for a = 9; when seeing the
expression a = 3 + 6, would be a problem for non-functional
languages.
I agree that things like [time.time() for i in xrange(10)] shouldn't
be pregenerated and that the problem is more complicated as I thought.
But during compilation the compilor could do an anlysis of the code
do determine whether there are side effects or not. If the compilor
then would store a code in the byte code for functions that are
guaranteed side-effect free and only pregenerated objects generated
by expressions with no side-effect, some common subexpression
elimination could be done even in a non-functional language.
Indeed, and it has been, which is a matter of well-recorded history. 
Constant folding has been used since the early Fortran compilers.

But you've already stated that the problem is more complicated than you 
thought. I presume you are already prepared to bail on any function that 
calls into external modules or extensions, since clearly nothing can be 
known about their behaviors vis a vis side effects.

Python is *designed* as a dynamic language. I wish you would embrace 
this aspect rather than continually trying to shoehorn it into a static 
straitjacket. Efficiency is good. Flexibility is better.

regards
 Steve
--
Steve Holden   http://www.holdenweb.com/
Python Web Programming  http://pydish.holdenweb.com/
Holden Web LLC  +1 703 861 4237  +1 800 494 3119
--
http://mail.python.org/mailman/listinfo/python-list

Re: [perl-python] 20050118 keyed list

[Jürgen Exner]

Xah Lee wrote:
> © # in perl, keyed-list is done like this:

Just FYI: those thingies are called hashes. The legacy name would be 
associative array.

> © %a = ('john',3, 'mary', 4, 'jane', 5, 'vicky',7);
> © use Data::Dumper qw(Dumper);
> © print Dumper \%a;

Wow, my compliments. The very first time that using Data::Dumper actually 
may do something useful (formats the data more nicely). Still, why you are 
passing a reference is beyond me.

> © # the syntax of keyed list in Perl is too complex
> © # to be covered in a short message.

Excuse me? If (using the same examples as for your Python section)
print "Mary is $a{mary}";
delete $a{vicky}; print %a;
print keys(%a);
exists $a{mary};
is too complex for your to cover, then I strongly suggest you stop posting 
your "explanations".

> © # see "perldoc perldata" for an unix-styled course.

Excuse me? Do you mind explaining where exactly perldata is "Unix-styled"?

jue 


-- 
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Re: lambda

[Antoon Pardon]

Op 2005-01-18, Steve Holden schreef <[EMAIL PROTECTED]>:
> Antoon Pardon wrote:
>
>> Op 2005-01-18, Nick Coghlan schreef <[EMAIL PROTECTED]>:
> [...]
>> But don't use mutable keys is not a general principle. It is a principle
>> introduced by the limitations of the python implementations.
>> 
> Sorry, but it *is* a general principle, adduced from the potential 
> pitfalls available to inexperienced programmers when breaking the principle.

But if these inexperienced programmers would have used dictionaries
that were implemented more safely, those pitfalls would have been
avoided. So are the pitfalls caused by breaking the principle
or by using an unsafe dictionary implementation?

>> I don't like it when a good rule of thumb because of implementation
>> limitations is sold as a general principle.
>> 
> So, since you are so good at nit-picking, perhaps you will explain the 
> difference between "rule of thumb" and "general principle".

A rule of thumb is context sensitive. If circumstances change,
so do the rules of thumb. Principles have a broader field
of application.

IMO there is nothing principally wrong with using a mutable object
as a dictionary key. But avoiding doing so is a good rule of
thumb if you have a python-like implementation of a dictionary.

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

bind error!!!!!

[Perrin Aybara]

hi..
my code was working pretty well until yesterday.suddenly it started
giving me bind error: address already in use.
but i have logged out and again logged in, but still the problem is not solved
can somebody give me solution for this

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

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Re: generator expressions: performance anomaly?

[Antoon Pardon]

Op 2005-01-18, Steve Holden schreef <[EMAIL PROTECTED]>:

> Python is *designed* as a dynamic language. I wish you would embrace 
> this aspect rather than continually trying to shoehorn it into a static 
> straitjacket. Efficiency is good. Flexibility is better.

Flexibility is better? IMO flexibilty implies more than one way to do
things. But that is a big no no here in c.l.py.

I also see a lot of remarks that go: "Don't do this!" when some of
the more dynamic aspects are talked about, because there are 
security risks involved. One of the results was that I ended up
writing a parser for some kind of game instead of just dumping the
structure in textual form and doing an eval of the file when reading
it in. But if I need a parser I could just as well used a static
language.

I'm beginning to guess the dynamic aspect of python is overrated.

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

RE: bind error!!!!!

[Batista, Facundo]

Title: RE: bind error!





[Perrin Aybara]


#- my code was working pretty well until yesterday.suddenly it started
#- giving me bind error: address already in use.
#- but i have logged out and again logged in, but still the 
#- problem is not solved
#- can somebody give me solution for this


Do you really think that somebody could help you with the information that you're giving?


You should read this: http://www.catb.org/~esr/faqs/smart-questions.html


Regards,


.    Facundo


Bitácora De Vuelo: http://www.taniquetil.com.ar/plog
PyAr - Python Argentina: http://pyar.decode.com.ar/



  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Re: MemoryError with parser.suite and wrong encoding declaration

[Thomas Heller]

Sylvain Thenault <[EMAIL PROTECTED]> writes:

> Hi there !
> I've noticed the following problem with python >= 2.3 (actually 2.3.4 and
> 2.4):
>
> [EMAIL PROTECTED]:test$ python
> Python 2.3.4 (#2, Sep 24 2004, 08:39:09)
> [GCC 3.3.4 (Debian 1:3.3.4-12)] on linux2
> Type "help", "copyright", "credits" or "license" for more information.
 import parser
 parser.suite('# -*- coding: IBO-8859-1 -*-')
> Traceback (most recent call last):
>   File "", line 1, in ?
> MemoryError
 parser.suite('# -*- coding: ISO-8859-1 -*-')
> 
>
> Shouldn't parser.suite just ignore the wrong encoding declaration, or at
> least raise a more appropriate exception. IMHO the first solution
> would be better, since that's the behaviour of the (C) python interpreter.

Ignore the wrong declaration?  All Python's that I have (on windows,
at least) raise a SyntaxError:

  File "x.py", line 1
SyntaxError: 'unknown encoding: IBO-8859-1'

See also:

http://www.python.org/sf/979739

Thomas
-- 
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Re: generator expressions: performance anomaly?

[Steve Holden]

Antoon Pardon wrote:
Op 2005-01-18, Steve Holden schreef <[EMAIL PROTECTED]>:

Python is *designed* as a dynamic language. I wish you would embrace 
this aspect rather than continually trying to shoehorn it into a static 
straitjacket. Efficiency is good. Flexibility is better.

Flexibility is better? IMO flexibilty implies more than one way to do
things. But that is a big no no here in c.l.py.
Become one with the language.
I also see a lot of remarks that go: "Don't do this!" when some of
the more dynamic aspects are talked about, because there are 
security risks involved. One of the results was that I ended up
writing a parser for some kind of game instead of just dumping the
structure in textual form and doing an eval of the file when reading
it in. But if I need a parser I could just as well used a static
language.

Wow, you mean you actually *took* some advice? :-) Perhaps this whole 
thing has arisen because you feel you were badly advised. It looks as 
though your programming skill level might have been underestimated. Your 
ability to wring an argument to a merciless death could never be.

I'm beginning to guess the dynamic aspect of python is overrated.
You shouldn't have to guess, and it isn't.
Certain of its dynamic aspects do demand a certain care rather than 
casual usage, however, which leads to rules of thumb like "don't use 
mutables as dictionary keys". Yes, of course you can, but to a newbie 
your behavior (it seems to me) is a bit like this:

Me (to newbie): "... And, of course, you want to be careful not to shoot 
yourself in the foot."

You: ":Well, actually, if you use a .22 and aim very carefully between 
the big toe and its neighbor there's a 96% chance that you will only 
suffer serious burns".

So, please understand, I'm not trying to say that (most of) your 
utterances are untrue, or question your knowledge of the Python 
environment. I'm just trying to bring the day closer when you will be 
able to watch me write something that's only 99% true and happily walk 
away without writing a thousand-word essay on the remaining 1% case.

This anal behavior is unlikely to win friends and influence people.
Anyway, I've just about had my say on this topic now. I'm left with the 
uncomfortable feeling that having led you patiently (or at least as 
patiently as I can) down to the water, I will now have to watch you die 
of thirst rather than take a well-deserved drink.

Life's too short. I'm going to stop disagreeing with you now, even if 
this means stopping communicating with you. I'm sure you won't miss my 
crotchety ramblings anyway.

regards
 Steve
--
Steve Holden   http://www.holdenweb.com/
Python Web Programming  http://pydish.holdenweb.com/
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Re: bind error!!!!!

[Steve Holden]

Perrin Aybara wrote:
hi..
my code was working pretty well until yesterday.suddenly it started
giving me bind error: address already in use.
but i have logged out and again logged in, but still the problem is not solved
can somebody give me solution for this
thankx
perrin
Next time, please ask a slightly smarter question:
www.catb.org/~esr/faqs/smart-questions.html
I presume you are talking about a socket-based server program?
There's a timeout period during which your server port will be left 
unusable (according to the TCP standards). You can avoid this by setting 
the socket.SO_REUSEADDR option when you open your server socket.

regards
 Steve
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script to automate GUI application (newbie)

[bogdan romocea]

Dear Python experts,

I have a GUI application (Windows; apparently written in Java) which I
want to use through a script (without a mouse or keyboard). First, one
of several buttons needs to be clicked (no keyboard shortcuts
available, but I can measure the coordinates in pixels from the top
left corner of the window to the center of the button to be clicked).
Then, a window with a few drop-down lists pops up - I have to make some
choices and click OK (it's possible to navigate from one drop-down to
the next with Tab, and hit Enter for OK). 

I want to run the script above from code (if this then click "... and
OK") and perhaps by means of several desktop shortcuts (one shortcut
for each set of GUI inputs). 

Is such a script possible? If yes, how do I get there? I searched
comp.lang.python but didn't find something directly applicable (or so
it seemed to me - I'm a beginner). Directions (and sample code, if
possible) will be warmly appreciated.

Thank you,
b.






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Re: Integration with java (Jpype vs. JPE)

[Istvan Albert]

Steve Menard wrote:
To asnwer your question more fully, the jpype-specific cide is only for 
looking up the Classes and startting/stopping the environment. For 
everything else, Java objects and classes are used as regular Python 
objects.
Thanks for the response. Currently I don't need to use java but
in the past when I explored such a possibility I looked at jpype
and I was unable to understand from the documentation what it
actually does.
There is a lot of text there, but it is all concerning catching
errors or other subtleties. For a new visitor the most important
question is about how it works, what does it do, and how can it be
applied for the given problem.
> everything else, Java objects and classes are used as regular Python
> objects.
This is too generic. My question was a little more specific,
how would I pass a python list as an argument of a java class/method or
transform a java list into a python one? You don't have to
answer it here, I'm just pointing out the kind of
questions that I was unable to get an answer for on the jpype
website.
best,
Istvan.
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Re: bind error!!!!!

[Fredrik Lundh]

Perrin Aybara wrote:

> my code was working pretty well until yesterday.suddenly it started
> giving me bind error: address already in use.

google has the details:

http://hea-www.harvard.edu/~fine/Tech/addrinuse.html

> but i have logged out and again logged in, but still the problem is not solved
> can somebody give me solution for this

and you're sure that nobody else on this computer is running a process
that's using the same port?  on most platforms, you can use "netstat" to
list all active connections and ports.

 



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RE: script to automate GUI application (newbie)

[Tim Golden]

[bogdan romocea]
| I have a GUI application (Windows; apparently written in Java) which I
| want to use through a script (without a mouse or keyboard). First, one
| of several buttons needs to be clicked (no keyboard shortcuts
| available, but I can measure the coordinates in pixels from the top
| left corner of the window to the center of the button to be clicked).
| Then, a window with a few drop-down lists pops up - I have to 
| make some
| choices and click OK (it's possible to navigate from one drop-down to
| the next with Tab, and hit Enter for OK). 
| 
| I want to run the script above from code (if this then click "... and
| OK") and perhaps by means of several desktop shortcuts (one shortcut
| for each set of GUI inputs). 
| 
| Is such a script possible? If yes, how do I get there? I searched
| comp.lang.python but didn't find something directly applicable (or so
| it seemed to me - I'm a beginner). Directions (and sample code, if
| possible) will be warmly appreciated.

Have a look at WATSUP. I think it's the kind of thing you're after.

http://www.tizmoi.net/watsup/intro.html

TJG


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Re: how to find site-packages path

[Eric S. Johansson]

Michael Hoffman wrote:
Philippe C. Martin wrote:
I am using my own install script for my software and am looking for a
flawless way to figure out where python, and more specifically
site-packages is installed.

The flawless way would be to use distutils. In fact you shouldn't even
need your own install script--it should do most of the work for you.
can distutils install in any directory?  for example, an application 
which has its own modules should be completely isolated from the general 
Python module namespace.  how would you make distutils install in a 
completely separate directory hierarchy and not touch any of the 
site-packages directories or files?

it looked like that was impossible from the documentation which is why I 
wrote my own installer.

---eric
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Re: Integration with java (Jpype vs. JPE)

[Joachim Boomberschloss]

Thanks for the info. I understand now the background
and possibilities, but would like to refine my query:
As I see it, writing a hybrid Java/Python application
faces approximately three possibilities: (i) write the
core in Java and do some scripting with Jython, (ii)
write independent code in Java and in Python, and
integrate using JPype (or similar), using Python also
as a glue layer, (iii) write independent code in Java
and in Python, and integrate using a neutral
technology.

Since much of the code in my project is already
written, I am considering options ii and iii. This is
how I perceive the work required in each case:

Option ii would enable writing independent packages in
Python and Java, and will require a glue layer in
Python consisting of general administration and
wrappers around Java packages written using JPype. I
don't yet have a clear perception of how difficult it
would be to make such wrappers, or to put my faith in
JPype at this stage.

Option iii would also enable writing independent
packages in Python and Java, but its glue layer will
be distributed between Python and Java using Jython
and Pyro (I chose Pyro because it works in both
CPython and Jython, and can be used to communicate
between them). This would (to the best of my
understanding) enable a smoother interface between
Java and Python, but will probably complicate somewhat
the glue layer, both because it would use networking
to communicate, and because it would probably involve
taking special measures to overcome the differences
between CPython and Jython (since the glue layer will
need to run on both of them).

Joe.
--- Cameron Laird <[EMAIL PROTECTED]> wrote:

> In article <[EMAIL PROTECTED]>,
> Jon Perez  <[EMAIL PROTECTED]> wrote:
> >Can someone summarize in a nutshell what is the
> >difference between JPype and JPE?
> 
> JPE's the original.  It provided more functionality
> than JPype has
> achieved so far, I believe (though that could change
> any day).  I
> think no one now maintains JPE.
> 
> Someone really ought to include a couple of
> sentences to that effect
> on the front page of http://jpype.sf.net/ >.
> -- 
> http://mail.python.org/mailman/listinfo/python-list
> 





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Re: Advice to a Junior in High School?

[Peter Hansen]

collegebabe2004 wrote:
I would suggest taking Japanese because you will have to work with them
eventually if you do decide to choose compsci as your proffesion.
Over what time frame should I expect this requirement to become
critical?  I'd like to know so I can reserve a spot in the next
Japanese course in the area, if you think it's really urgent.
Also, should I plan on adopting various aspects of the Japanese
culture as well, or will a mastery of the language be sufficient?
-Peter
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Re: MemoryError with parser.suite and wrong encoding declaration

[Sylvain Thenault]

On Tue, 18 Jan 2005 16:16:32 +0100, Thomas Heller wrote:

> Sylvain Thenault <[EMAIL PROTECTED]> writes:
> 
>> Hi there !
>> I've noticed the following problem with python >= 2.3 (actually 2.3.4
>> and 2.4):
>>
>> [EMAIL PROTECTED]:test$ python
>> Python 2.3.4 (#2, Sep 24 2004, 08:39:09) [GCC 3.3.4 (Debian 1:3.3.4-12)]
>> on linux2 Type "help", "copyright", "credits" or "license" for more
>> information.
> import parser
> parser.suite('# -*- coding: IBO-8859-1 -*-')
>> Traceback (most recent call last):
>>   File "", line 1, in ?
>> MemoryError
> parser.suite('# -*- coding: ISO-8859-1 -*-')
>> 
>>
>> Shouldn't parser.suite just ignore the wrong encoding declaration, or at
>> least raise a more appropriate exception. IMHO the first solution would
>> be better, since that's the behaviour of the (C) python interpreter.
> 
> Ignore the wrong declaration?  All Python's that I have (on windows, at
> least) raise a SyntaxError:
> 
>   File "x.py", line 1
> SyntaxError: 'unknown encoding: IBO-8859-1'

hum, right (with python >= 2.3 which is the first release using those
declaration...). I was sure to have checked this but I've obviously
missed something. Maybe the fact that being able to parse it anyway is
the solution I wish has driven me to write this ;) I would like this
behaviour so that pylint can check a module with a wrong encoding
declaration anyway. But at least, SyntaxError would be better than
MemoryError.

> See also:
> 
> http://www.python.org/sf/979739

thanks
-- 
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http://www.logilab.com   http://www.logilab.fr  http://www.logilab.org


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Re: script to automate GUI application (newbie)

[Grig Gheorghiu]

Bogdan,

If your app is written in Java, take a look at Marathon
(http://marathonman.sourceforge.net/). It uses Jython as its scripting
language and it's pretty smart about how it does automation (i.e. it
doesn't look at screen coordinates, but at control names). It also
offers a capture/replay functionality, and it automatically builds the
Jython script that drives your flow of actions. You can then edit and
enhance the script manually.

Grig

bogdan romocea wrote:
> Dear Python experts,
>
> I have a GUI application (Windows; apparently written in Java) which
I
> want to use through a script (without a mouse or keyboard). First,
one
> of several buttons needs to be clicked (no keyboard shortcuts
> available, but I can measure the coordinates in pixels from the top
> left corner of the window to the center of the button to be clicked).
> Then, a window with a few drop-down lists pops up - I have to make
some
> choices and click OK (it's possible to navigate from one drop-down to
> the next with Tab, and hit Enter for OK).
>
> I want to run the script above from code (if this then click "... and
> OK") and perhaps by means of several desktop shortcuts (one shortcut
> for each set of GUI inputs).
>
> Is such a script possible? If yes, how do I get there? I searched
> comp.lang.python but didn't find something directly applicable (or so
> it seemed to me - I'm a beginner). Directions (and sample code, if
> possible) will be warmly appreciated.
>
> Thank you,
> b.
>
>
>
>
>
>
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> Yahoo! Mail - Easier than ever with enhanced search. Learn more.
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simultaneous multiple requests to very simple database

[Eric S. Johansson]

I have an application where I need a very simple database, effectively a 
very large dictionary.  The very large dictionary must be accessed from 
multiple processes simultaneously.  I need to be able to lock records 
within the very large dictionary when records are written to.  Estimated 
number of records will be in the ballpark of 50,000 to 100,000 in his 
early phase and 10 times that in the future.  Each record will run about 
100 to 150 bytes.

speed is not a huge concern although I must complete processing in less 
than 90 seconds.  The longer the delay however the greater number of 
processes must be running parallel in order to keep the throughput up. 
It's the usual trade-off we have all come to know and love.

it is not necessary for the dictionary to persist beyond the life of the 
parent process although I have another project coming up in which this 
would be a good idea.

at this point, I know they will be some kind souls suggesting various 
SQL solutions.  While I appreciate the idea, unfortunately I do not have 
time to puzzle out yet another component.  Someday I will figure it out 
because I really liked what I see with SQL lite but unfortunately, today 
is not that day (unless they will give me their work, home and cell 
phone numbers so I can call when I am stuck. ;-)

So the solutions that come to mind are some form of dictionary in shared 
memory with locking semaphore scoreboard or a multithreaded process 
containing a single database (Python native dictionary, metakit, gdbm??) 
and have all of my processes speak to it using xmlrpc which leaves me 
with the question of how to make a multithreaded server using stock xmlrpc.

so feedback and pointers to information would be most welcome.  I'm 
still exploring the idea so I am open to any and all suggestions (except 
maybe SQL :-)

---eric
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Re: Advice to a Junior in High School? [OT]

[TZOTZIOY]

On Tue, 18 Jan 2005 11:04:01 -0500, rumours say that Peter Hansen
<[EMAIL PROTECTED]> might have written:

>collegebabe2004 wrote:
>> I would suggest taking Japanese because you will have to work with them
>> eventually if you do decide to choose compsci as your proffesion.

[Peter]
>Over what time frame should I expect this requirement to become
>critical?  I'd like to know so I can reserve a spot in the next
>Japanese course in the area, if you think it's really urgent.
>Also, should I plan on adopting various aspects of the Japanese
>culture as well, or will a mastery of the language be sufficient?

I think having a katana next to your keyboard will suffice to give the
*impression* you have mastered enough of the japanese culture, Peter :)
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I really should keep that in mind when talking with people, actually...
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makepy crashing

[markscottwright]

Has anyone sucessfully run makepy and Microsoft Word Object Library
(9.0)?  Mine crashes under XP Pro and Python 2.4.

It only seems to be word that has the problem, though.

I get a dialog that says that pythonwin.exe has crashed:
AppName: pythonwin.exe   AppVer: 0.0.0.0 ModName: ntdll.dll
ModVer: 5.1.2600.1217Offset: 96f9

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Re: [perl-python] 20050118 keyed list

[Tassilo v. Parseval]

Also sprach Jürgen Exner:

> Xah Lee wrote:

>> © %a = ('john',3, 'mary', 4, 'jane', 5, 'vicky',7);
>> © use Data::Dumper qw(Dumper);
>> © print Dumper \%a;
>
> Wow, my compliments. The very first time that using Data::Dumper actually 
> may do something useful (formats the data more nicely). Still, why you are 
> passing a reference is beyond me.

How else would you use 'Dumper' on a hash?

Tassilo
-- 
$_=q#",}])!JAPH!qq(tsuJ[{@"tnirp}3..0}_$;//::niam/s~=)]3[))_$-3(rellac(=_$({
pam{rekcahbus})(rekcah{lrePbus})(lreP{rehtonabus})!JAPH!qq(rehtona{tsuJbus#;
$_=reverse,s+(?<=sub).+q#q!'"qq.\t$&."'!#+sexisexiixesixeseg;y~\n~~;eval
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RE: simultaneous multiple requests to very simple database

[Robert Brewer]

Eric S. Johansson wrote:
> I have an application where I need a very simple database, 
> effectively a very large dictionary.  The very large
> dictionary must be accessed from multiple processes
> simultaneously.  I need to be able to lock records within
> the very large dictionary when records are written to.

Just to clarify, you want shared-read until a write, at which point you
want to lock just the item being written? Or would page or table locking
be acceptable at that point?


Robert Brewer
MIS
Amor Ministries
[EMAIL PROTECTED]
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One-Shot Property?

[Kevin Smith]

I have many cases in my code where I use a property for calculating a 
value on-demand.  Quite a few of these only need to be called once.  
After that the value is always the same.  In these properties, I set a 
variable in the instance as a cached value and return that value on 
subsequent calls.  It would be nice if there was a descriptor that would 
do this automatically.  Actually, what would be really nice is if I 
could replace the property altogether and put the calculated value in 
its place after the first call, but the property itself prevents me from 
doing that.  Is this possible?

-- 
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[EMAIL PROTECTED]
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Re: [perl-python] 20050118 keyed list

[Reinhold Birkenfeld]

Jay Tilton wrote:

>: # the syntax of keyed list in Perl is too complex
>: # to be covered in a short message.

JFTR: "keyed lists" are called dictionaries in Python.

> 
> [1]Message-ID: <[EMAIL PROTECTED]>
> 

This guy's wish-wash is starting to be funny, after all!

Reinhold
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Tkinter in thread hangs on windows but not on Linux

[Philippe C. Martin]

Hi,

I need to pop-up in a "modless" manner some windows from an existing
Tkinter loop. The following code works OK under Linux: the second window
opens, shows the information, and quits cleanly when destroyed. However,
under windows, I get the second window without the content (so I hang in
run I guess), and both the thread and the calling process hang.

Any clue ?

Thanks
Philippe





#***
class SC_DOCS(threading.Thread):
  __m_smg = None
  __m_title = None
  def __init__(self,p_msg,p_title):
threading.Thread.__init__(self)
self.__m_msg = p_msg
self.__m_title = p_title

#***
  def run (self):
l_r = Tk()
l_r.title(self.__m_title)
l_f = Frame(l_r)
l_f.pack(side=TOP, expand=YES, fill=BOTH)
l_st = ScrolledText(l_f)
l_st.pack(side=TOP, expand=YES, fill=BOTH)
l_st.insert(END,self.__m_msg)

l_r.mainloop()


.
.
.

l_d = SC_DOCS('A MESSAGE', 'A TITLE')
l_d.start()


.
.
.
-- 
***
Philippe C. Martin
SnakeCard LLC
www.snakecard.com
***

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Re: [perl-python] 20050118 keyed list

[Reinhold Birkenfeld]

Jürgen Exner wrote:

>> © # see "perldoc perldata" for an unix-styled course.
> 
> Excuse me? Do you mind explaining where exactly perldata is "Unix-styled"?

Remember: Perl == Unix == Satan.

Reinhold
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Re: simultaneous multiple requests to very simple database

[Eric S. Johansson]

Robert Brewer wrote:
Eric S. Johansson wrote:
I have an application where I need a very simple database, 
effectively a very large dictionary.  The very large
dictionary must be accessed from multiple processes
simultaneously.  I need to be able to lock records within
the very large dictionary when records are written to.

Just to clarify, you want shared-read until a write, at which point you
want to lock just the item being written? Or would page or table locking
be acceptable at that point?
just the item/record.  I'm doing arrival rate calculations.  each record 
contains a set of arrival times and I am rewriting the record every time 
a new entry arrives.  complete page or table locking will work in the 
sense that it will prevent collisions but it will have an increasing 
impact as load and simultaneous table but not record accesses increase.

---eric
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Re: One-Shot Property?

[Dave Benjamin]

Kevin Smith wrote:
I have many cases in my code where I use a property for calculating a 
value on-demand.  Quite a few of these only need to be called once.  
After that the value is always the same.  In these properties, I set a 
variable in the instance as a cached value and return that value on 
subsequent calls.  It would be nice if there was a descriptor that would 
do this automatically.  Actually, what would be really nice is if I 
could replace the property altogether and put the calculated value in 
its place after the first call, but the property itself prevents me from 
doing that.  Is this possible?
I was going to recommend taking a look at the "memoize" example on the 
Python wiki, but it seems to be missing at the moment. In any case, 
here's the URL:

http://www.python.org/moin/PythonDecoratorLibrary
There are also a few examples on the Cookbook, like this one:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/325205
It shouldn't be too difficult to adapt this technique so that it can be 
used to create properties. I wouldn't bother replacing the property with 
an attribute unless you have a specific reason to do so (performance, 
perhaps).

HTH,
Dave
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Re: script to automate GUI application (newbie)

[Jim]

It sounds like a case for the Expect program, to me.  Try Google-ing
for "Expect".  If you are looking for a Python approach, then try
googling for "Expect Python".

Jim

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Re: One-Shot Property?

[Daniel Dittmar]

Kevin Smith wrote:
I have many cases in my code where I use a property for calculating a 
value on-demand.  Quite a few of these only need to be called once.  
After that the value is always the same.  In these properties, I set a 
variable in the instance as a cached value and return that value on 
subsequent calls.  It would be nice if there was a descriptor that would 
do this automatically.  Actually, what would be really nice is if I 
could replace the property altogether and put the calculated value in 
its place after the first call, but the property itself prevents me from 
doing that.  Is this possible?
If you use the old-fashioned __getattr__ method instead of properties. 
__getattr__ gets called only if the value can't be found in the instance 
dictionary.

def __getattr__ (self, attrname):
try:
method = getattr (self, 'calculate_' + attrname)
except AttributeError:
raise AttributeError, attrname
value = method ()
setattr (self, attrname, value)
return value
And probably also through metaclasses. And decorators.
Daniel
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Re: generator expressions: performance anomaly?

[Jeremy Bowers]

On Tue, 18 Jan 2005 14:05:15 +, Antoon Pardon wrote:
> I don't see how generating byte code for a = 9; when seeing the
> expression a = 3 + 6, would be a problem for non-functional
> languages.

To answer nearly every post you've made to this thread, "because Python
doesn't have the resources to program to special cases".

And as is often the case in this sort of discussion, sure, adding this
might be only a little work, but there's thousands of enhancements of the
same general work level and performance gain. So remember you're not just
espousing this particular enhancement, you're implicitly arguing for the
entire class (because there is nothing to discriminate in the argument
"this is fairly easy" between this particular feature on your mind today
and the other thousands of such features).

To address your point more specifically, you can do this subexpression
elimination to the extent that your expression is a purely functional one.
"a = 3 + 6", while written in an imperative language and setting a
variable in an imperative manner, has a "functional subexpression" "3 +
6", that has no side-effects, etc., so the compiler could reduce it if it
knew how. (In Python, that's a function call, but since you can't change
__add__ on ints, you could do this, although there's still some special
casing you're doing that will ripple unpleasantly through the code.) But
as soon as you call any sort of method or function, you're done.

Ultimately, the use is fairly limited; I can't imagine the execution time
saved would reach the time of implementation for weeks after a release,
even aggregating across all Python use in the world, and "real time
gained" (i.e., time useful to a human) would probably never add up to the
implementation time. So why bother? That's a horrid trade off when there
are so many other real gains to be had.

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Re: ANNOUNCE: Altova ... blah blah blah

[Irmen de Jong]

Altova Announcements wrote:
Altova Unveils .
[spam]
Well now, I didn't like their products very much already,
but this spam has certainly made them drop another few
steps down on my scale. Hmpf.
--Irmen
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Re: One-Shot Property?

[Leif K-Brooks]

Kevin Smith wrote:
I have many cases in my code where I use a property for calculating a 
value on-demand.  Quite a few of these only need to be called once.  
After that the value is always the same.  In these properties, I set a 
variable in the instance as a cached value and return that value on 
subsequent calls.  It would be nice if there was a descriptor that would 
do this automatically.  Actually, what would be really nice is if I 
could replace the property altogether and put the calculated value in 
its place after the first call, but the property itself prevents me from 
doing that.
This should do it:
class CachingProperty(object):
def __init__(self, attr_name, calculate_function):
self._name = attr_name
self._calculate = calculate_function
def __get__(self, obj, type=None):
if obj is None:
return self
else:
value = self._calculate(obj)
setattr(obj, self._name, value)
return value
And example code:
>>> class Foo(object):
... def calculate_value(self):
... print 'Calculating...'
... return 42
... foo = CachingProperty('foo', calculate_value)
...
>>> bar = Foo()
>>> bar.__dict__
{}
>>> bar.foo
Calculating...
42
>>> bar.foo # Notice that the print statement doesn't run this time
42
>>> bar.__dict__
{'foo': 42}
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Re: Integration with java (Jpype vs. JPE)

[Irmen de Jong]

Joachim Boomberschloss wrote:
Option iii would also enable writing independent
packages in Python and Java, but its glue layer will
be distributed between Python and Java using Jython
and Pyro (I chose Pyro because it works in both
CPython and Jython, and can be used to communicate
between them).
Please note that currently it is not possible to use Pyro
as a server in Jython. Only as a client.
Also; last time I checked there were some bugs in the Jython
compiler that were triggered by Pyro's code (parts of it
would give a compile error).
See http://www.razorvine.net/python/PyroAndJython
--Irmen
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Re: One-Shot Property?

[John Lenton]

On Tue, Jan 18, 2005 at 04:54:56PM +, Kevin Smith wrote:
> 
> I have many cases in my code where I use a property for calculating a 
> value on-demand.  Quite a few of these only need to be called once.  
> After that the value is always the same.  In these properties, I set a 
> variable in the instance as a cached value and return that value on 
> subsequent calls.  It would be nice if there was a descriptor that would 
> do this automatically.  Actually, what would be really nice is if I 
> could replace the property altogether and put the calculated value in 
> its place after the first call, but the property itself prevents me from 
> doing that.  Is this possible?

consider this:

   1 >>> class C:
   2 ... x = property(str)
   3 ... 
   4 >>> c = C()
   5 >>> c.x
   6 '<__main__.C instance at 0x4008d92c>'
   7 >>> setattr(c, 'x', c.x)
   8 >>> c.x
   9 '<__main__.C instance at 0x4008d92c>'
  10 >>> C.x
  11 
  12 >>> c.x = 2
  13 >>> 

in line 5 you see that the x property so defined works. In line 7 you
remove it, replacing it with the computed value of the property. Line
9 shows that it worked, line 11 shows that it didn't break the class,
and line 13 (through the absence of an exception) shows that it no
longer is 'special' (as it shouldn't be).

-- 
John Lenton ([EMAIL PROTECTED]) -- Random fortune:
You can tune a piano, but you can't tuna fish.

You can tune a filesystem, but you can't tuna fish.
-- from the tunefs(8) man page


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Print to Windows default Printer

[Samantha]

I am new to Python and I am having considerable trouble trying to print 
(using a simple script) to the default printer rather than the screen.
Thanks for any help.
S 


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Re: Print to Windows default Printer

[Peter Hansen]

Samantha wrote:
I am new to Python and I am having considerable trouble trying to print 
(using a simple script) to the default printer rather than the screen.
Thanks for any help.
Please show some example code, and explain in more detail
what you are trying to do.  There are perhaps *dozens*
of different ways to do printing under Windows, and we
can't guess which approach you are trying, nor which
might be suitable for your needs.
-Peter
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hex notation funtion

[tertius]

Hi,
Is there a builtin function that will enable me to display the hex 
notation of a given binary string? (example below)

many thanks
Tertius

()  02 11 00 00 46 5A 1A 82  02 11 00 39 36 39 33 39 
FZ.96939

0016(0010)  36 39 33 00 0A 30 33 37  34 34 39 35 38 25 DD 01 
693..03744958%..
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pickling extension class

[harold fellermann]

Hi all,
I have a problem pickling an extension class. As written in the 
Extending/Embedding Manual, I
provided a function __reduce__ that returns the appropreate tuple. This 
seams to work fine,
but I still cannot pickle because of the following error:

>>> from model import hyper
>>> g = hyper.PeriodicGrid(4,4,1)
>>> g.__reduce__()
(,(4.,4.,1.))
>>> import pickle
>>> pickle.dump(g,file("test","w"))
Traceback (most recent call last):
  File "pickle_test.py", line 5, in ?
pickle.dump(g,file("test","w"))
  File "/sw/lib/python2.4/pickle.py", line 1382, in dump
Pickler(file, protocol, bin).dump(obj)
  File "/sw/lib/python2.4/pickle.py", line 231, in dump
self.save(obj)
  File "/sw/lib/python2.4/pickle.py", line 338, in save
self.save_reduce(obj=obj, *rv)
  File "/sw/lib/python2.4/pickle.py", line 414, in save_reduce
save(func)
  File "/sw/lib/python2.4/pickle.py", line 293, in save
f(self, obj) # Call unbound method with explicit self
  File "/sw/lib/python2.4/pickle.py", line 760, in save_global
raise PicklingError(
pickle.PicklingError: Can't pickle : it's 
not found as hyper.PeriodicGrid
>>> dir(hyper)
['Dir', 'Neighbors', 'PeriodicGrid', 'PeriodicPos', '__doc__', 
'__file__', '__name__', 'refcount']
>>> hyper.PeriodicGrid


So pickle complains about the class PeriodicGrid not being found in the 
module hyper, but a dir()
proves that python can find it. Has anyone an idea what's going wrong 
here?

Any help appreceated,
- harold -
--
What is mind? -- Doesn't matter.
What is matter? -- Never mind!
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Re: hex notation funtion

[Irmen de Jong]

tertius wrote:
Hi,
Is there a builtin function that will enable me to display the hex 
notation of a given binary string? (example below)
Does this help:
>>> "hello".encode("hex")
'68656c6c6f'
>>> "deadbeef".decode("hex")
'\xde\xad\xbe\xef'
?
--Irmen
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Re: hex notation funtion

[Philippe C. Martin]

Would that do it?

for i in my_byte_string:
   = atoi(binascii.hexlify(i),16)

Regards,

Philippe





On Tue, 18 Jan 2005 20:43:44 +0200, tertius wrote:

> Hi,
> 
> Is there a builtin function that will enable me to display the hex 
> notation of a given binary string? (example below)
> 
> many thanks
> Tertius
> 
> 
> 
> ()  02 11 00 00 46 5A 1A 82  02 11 00 39 36 39 33 39 
> FZ.96939
> 
> 0016(0010)  36 39 33 00 0A 30 33 37  34 34 39 35 38 25 DD 01 
> 693..03744958%..

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