How do you use this list ?

[Bo Yang]

Hi everyone ,
I have join this list for about 4 months , and everyday I receive
hundreds of
mails . There is no means to read all of them , so I just read something
interesting
for me . But if so , there are too much mails pile up in my inbox , I
want to ask
how do you use this list , reading every mail come in or just read what
you think
interesting ?

Thank you !


Best Regard !
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Re: TypeError: Cannot create a consistent method resolution order (MRO) for bases object

[Michele Simionato]

[EMAIL PROTECTED] wrote:
> What are the reason one would get this error: TypeError: Cannot create
> a consistent method resolution order (MRO) for bases object ??

See http://www.python.org/download/releases/2.3/mro/

 Michele Simionato

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Re: logging error with RotatingFileHandler

[Vinay Sajip]

flupke wrote:

>   File "C:\Python24\lib\logging\handlers.py", line 134, in doRollover
> self.handleError(record)
> NameError: global name 'record' is not defined

There's a bug in doRollover's exception handling, which is masking the
true error - which is most probably an exception being thrown in
os.rename.

I'll look at fixing this bug asap. Most likely, it'll be done by let
the exception propagate up from doRollover to its caller.

Regards,

Vinay Sajip

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Re: Termination and type systems

[Dirk Thierbach]

David Hopwood <[EMAIL PROTECTED]> wrote:
> Dirk Thierbach wrote:

> That's interesting, but linear typing imposes some quite severe
> restrictions on programming style. From the example of 'h' on page 2,
> it's clear that the reason for the linearity restriction is just to
> ensure polynomial-time termination, and is not needed if we only want
> to prove termination.

Yes. It's just an example of what can be actually done with a typesystem.

>> It's already hard enough to guarantee termination with the extra
>> information present in the type annotation. If this information is
>> not present, then the language has to be probably restricted so
>> severely to ensure termination that it is more or less useless.

> I think you're overestimating the difficulty of the problem. The fact
> that *in general* it can be arbitrarily hard to prove termination, can
> obscure the fact that for large parts of a typical program, proving
> termination is usually trivial.

Yes. The problem is the small parts where it's not trivial (and the
size of this part depends on the actual problem the program is trying
to solve). Either you make the language so restrictive that these
parts are hard (see your remark above) or impossible to write, or
you'll be left with a language where the compiler cannot prove
termination of those small parts, so it's not a "type system" in the
usual sense.

Of course one could write an optional tool that automatically proves
termination of the easy parts, and leaves the rest to the programmer,
but again, that's a different thing.

- Dirk
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Re: break the loop in one object and then return

[Petr Jakes]

Alex Pavluck wrote:
> Peter,  Why do you make such claims without any reason to do so?  This
> is my own thing.  So, I guess I am a student but just a student of my
> own accord.  So, please don't reply if you don't have anything to
> contribute.
First:
This is not "YOUR OWN THING". This group really can help, but this
group AFAIK does not write homeworks. It is nothing wrong you are just
a student, we are all students somehow :)

Second:
Few other posters were posting similar requests to this group last few
days (maybe your classmates :)) so the chance it just a coincidence is
very low. If I am wrong, sorry about that.

Third:
This group can help, but some effort (study, googling this group etc.)
on your side is necessary as well. Other posters suggested you the way,
where to go, but you didn't try to change your code a bit. Please read
the following as well:
http://www.albion.com/netiquette/corerules.html

To your code:
>
> As for the - mynum I guess that could happen but I am just doing this
> so that they will never match on first try.  I guess I should just
> hardcode it.
>
> This is what happens if I step though:
>
> mynum = 93***1***

use # sign for your comments in the code followed by the comment text.
All the stuff after the # is ignored when the code is executed. Nobody
can execute (examine) your code whit your comments like ***1***

To hardcode "mynum" value is IMHO very bad idea and your code will be
useless if the value will be "discovered". Other suggested how to
generate random number at the beginning of the code.

> yournum = input("I am thinking of a number between 1 and 100.\n  Guess
> which number: ")   ***2***
>
> def strt():  ***3******6***
> if yournum == mynum: ***7***
> print "Wow!  You got it!"
> elif yournum < mynum:  ***8***
> print "Nope.  Too low"   ***9***
> again()***10***  ***15***
> elif yournum > mynum:
> print "Oh, your too high"
>
> def again(): ***4*** ***11***
> global yournum   ***12***
> yournum = input("guess again: ")  ***13***
> strt()  ***14***
>
> strt()  ***5***
>
>
> ***15***  is the problem.  It doesn't start at the top but rather where
> is leaves the loop.

print statement can help to solve your problem, put it (with some text
that will navigate you) on the rows where you are not sure the program
is not running properly. Print out the values of the mynum and yournum
as well. This will be just for your "debugging" purposes. Finally you
will remove it.

For example you can put:
print "starting the strt function", "mynum = ", mynum, "yournum =",
yournum

on the first row of your strt function, so you will see the code is
going through there.

Finally:
Try to thing what will happen if the person will input character rather
than integer.

Again: good luck in your effort

Petr Jakes
>
>
>
>
>
> Petr Jakes wrote:
> > It smells like many student are trying to do their homework last few
> > days here ... Can we now the name of your school? :)
> >
> > AFAIK this group does not solve homeworks here :)
> >
> > Just few points:
> >
> > at the beginning try to test the input value
> > you can use "in range" or using "0 < yournum  < 101"
> >
> > you should test if the input is an integer as well..
> > http://tinyurl.com/j468c
> >
> > Other suggested here which way to go.
> > 
> > Good luck :)
> > 
> > Petr Jakes

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Re: How do you use this list ?

[placid]

Bo Yang wrote:
> Hi everyone ,
> I have join this list for about 4 months , and everyday I receive
> hundreds of
> mails . There is no means to read all of them , so I just read something
> interesting
> for me . But if so , there are too much mails pile up in my inbox , I
> want to ask
> how do you use this list , reading every mail come in or just read what
> you think
> interesting ?
>

your recieving those emails because you choose (in your My Account
settings) to received emails, you can deselect this and then just read
any post that interests you and ask questions of your own.

Cheers

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Re: What is Expressiveness in a Computer Language

[Ketil Malde]

"Marshall" <[EMAIL PROTECTED]> writes:

> There are also what I call "packaging" issues, such as
> being able to run partly-wrong programs on purpose so
> that one would have the opportunity to do runtime analysis
> without having to, say, implement parts of some interface
> that one isn't interested in testing yet. These could also
> be solved in a statically typed language. (Although
> historically it hasn't been done that way.)

I keep hearing this, but I guess I fail to understand it.  How
"partly-wrong" do you require the program to be?

During development, I frequently sprinkle my (Haskell) program with
'undefined' and 'error "implement later"' - which then lets me run the
implemented parts until execution hits one of the 'undefined's.

The "cost" of static typing for running an incomplete program is thus
simply that I have to name entities I refer to.  I'd argue that this
is good practice anyway, since it's easy to see what remains to be
done. (Python doesn't seem to, but presumably a serious dynamically
typed system would warn about references to entities not in scope?) 

-k
-- 
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Re: What technologies should I use for my application manager?

[MrBlueSky]

Thanks for the advice, Adam!

Turbogears sounds like it does everything I want and looks like a
great...  except you've made me nervous with your comment on the
instability of the Oracle API!

Stability, good documentation and a wide user base are priorities.  I
was delighted by the quality of Tkinter in this regard.  Am I wishing
for the moon in hoping for the same quality in the framework I choose
for this?

Anyone else like to try and sell me on Zope or Django?!

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Re: How do I limit access to objects in Python?

[Diez B. Roggisch]

Tommytrojan schrieb:
> Hi,
> 
> I have an application that embeds the Python interpreter. My users have 
> access to the interpreter through a console like window and they can run 
> Python scripts. For my application I use some Python modules (say module 
> Restricted) that I don't want to give my users access to. However, the 
> modules that I make public to my users and that I want my users to be 
> able to use themselves use the Restricted module. Any suggestions on how 
> to solve this? I was thinking of instantiating a separate interpreter 
> but I don't think this will solve my problem.

I don't think that is possible - how is one to distinguish your code 
from the code written by a user that calls one method in the restricted 
module?

What you _can_ do is to spawn an interpreter, and expose the allowed 
objects via Pyro.


The question is though: why cripple your users? If someone could reach 
an otherwise unreachable goal why do yoou hinder him? What is the 
reasoning behind that?

Diez
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Re: style question

[Hari Sekhon]

On 26/06/06, Claudio Grondi <[EMAIL PROTECTED]> wrote:
Scott David Daniels wrote:> Claudio Grondi wrote:> <<> When necessary to skip first line _and_ indentation:>>   message = """
>>   This is line 1>>   This is line 2>>   This is line 3>>   """.replace('\n  ', '\n')[1:] # adjust here '\n  ' to indentation>>> Riffing on this idea:
> message = """>   This is line 1>   This is line 2>   This is line 3>   """.replace(""">   """, '\n')[1:]
This was intended as an excercise for the OP in case he likes that kindof solution ...Claudio>> --Scott David Daniels> [EMAIL PROTECTED]
--http://mail.python.org/mailman/listinfo/python-listI've decided to go with

    message = (        "This is line1. "        "This is line2 "        "This is line3\n")

since I'm declaring many different messages inside various functions I
feel it is important to keep the indentaion and code both aligned
properly so the code looks nice and the output looks nice.

It is easier than doing replace and splicing since I want to keep it as
simple and clean as possible, in true pythonic tradition...

Thanks for the input!

-h

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Re: What technologies should I use for my application manager?

[Fredrik Lundh]

"MrBlueSky" wrote:

> Anyone else like to try and sell me on Zope or Django?!

start here:

http://www.djangoproject.com/documentation/tutorial1/

if you're on windows, and just want to tinker a little,

http://effbot.org/zone/django.htm#installing

might also be helpful.

 



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Re: A game idea.

[Max M]

defcon8 wrote:
> I have had what I think is quite a nice game idea, but I don't really
> have the experience or knowledge to go about it. Would anyone be
> willing to start a game project?


Ideas are a dime a dozen. Implementation is the hard part.

If you want something done, you will have to do it yourself.

I am not trying to be negative, but I will bet you that every competent 
programmer on the list has 1+ project that she would love to do, if she 
just had the time.

-- 

hilsen/regards Max M, Denmark

http://www.mxm.dk/
IT's Mad Science

Phone:  +45 66 11 84 94
Mobile: +45 29 93 42 96
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to py or not to py ?

[Chandrashekhar kaushik]

HI all I have the following prob.I am to write a parallel vis application .I wud have by default used C++ for the same but somehow thought if py cud help me ..It does as in many things that i would otherwise have written down
already exists ... ( like built in classes for sockets , threading etc )I would be doin the following type of tasks .. 1. sending data across the network     the data is going to be huge2. once data has been sent i will run some vis 
    algos parallely on them and get the resultsnow one thing that i wud req. is serializing my data structures so that they can be sent across the net.pyton does allow this using cPickle , but it bloats the data like anythin !!! 
for example a class containing 2 integers which i expect will be 8 bytes long ..cPickle.dumps returns a string thats 86 bytes wide  ( this is the binary version protocol 1 )anyway to improve serialization ??
also is it actually a good idea to write high perf applications in python ?thanks in advance-
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Re: Replace Whole Object Through Object Method

[I V]

On Mon, 26 Jun 2006 19:40:52 -0700, digitalorganics wrote:
> A misuse of inheritance eh? Inheritance, like other language features,
> is merely a tool. I happen to be using this tool to have my virtual
> persons change roles at different points in their lifetime, as many
> real people tend to do. Thus, at these points, B is indeed an A. What a
> person is, whether in real life or in my program, is not static and
> comes into definition uniquely for each moment (micro-moment, etc.) of
> existence. Now, please, I have no intention of carrying the
> conversation in such a silly direction, I wasn't inviting a discussion
> on philosophy or some such. I seek to work the tools to my needs, not
> the other way around.

But thinking about the problem in the vocabulary provided by the
programming language can be helpful in coming up with a solution. If
inheritance tells you what an object _is_, and membership tells you what a
role _has_, and a role is something that a person has, that suggests
that an implementation where roles are members of a person might be
simpler than trying to use inheritance. Like, for instance:

class Role(object):
def __init__(self, person):
self.person = person


class Worker(Role):
def do_work(self):
print self.name, "is working"


class Employer(Role):

def __init__(self, person):
Role.__init__(self, person)
self.employees = []


def add_employee(self, worker):
self.employees.append(worker)


def boss_people_around(self):
for employee in employees:
print self.name, "is telling", employee.name, "what to 
do"


class Person(object):

def __init__(self, name):
self.roles = []
self.name = name


def add_role(self, role_class):
self.roles.append(role_class(self))


def forward_to_role(self, attr):
for role in self.roles:
try:
return getattr(role, attr)
except AttributeError:
pass
raise AttributeError(attr)


def __getattr__(self, attr):
self.forward_to_role(attr)


bill = Person('Bill')
bill.add_role(Worker)

bob = Person('Bob')
bob.add_role(Employer)

bill.work()
bob.boss_people_around()

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Re: Replace Whole Object Through Object Method

[Bruno Desthuilliers]

Maric Michaud wrote:
> Le lundi 26 juin 2006 22:37, [EMAIL PROTECTED] a écrit :
> 
>>Won't work because there will be employers that aren't workers.
>>And yes, only some workers will become employers, but also only some
>>employers will also be workers (at some point in program). Let me be
>>more clear:
>>
>>workers
>>--> subset of workers --become--> employers
>>employers
>>--> subset of employers --become--> workers
>>
>>It is very important that both should maintain attribute values,
>>regardless of whether they take on new "roles". Furthermore, this is a
>>very simple case and ultimately in my program an object should be able
>>to dynamically take on a multitude of roles (classes of behavior)
>>without mucking at all with their pre-existing states.
> 
> 
> This seem to be a OO design problem

Obviously.

> and you clearly make a misuse of 
> inheritance,

Chapter and verse, please ?
s/misuse/creative use/

> if a person can eventually have many roles, but doesn't have 
> this role for all his lifetime, then the person *is* not his roles.

And ? In a dynamically typed language, inheritance is about
implementation, not subtyping. The class of an object is nothing more
than an attribute, and as such is not necessarily fixed for the lifetime
of the object.

> That the meaning of inheritance, class B(A) means a B is a A.
> The association between a person and his roles is obviously a 1-n 
> association, 
> which can be rendered by different patterns (delegation, composition, 
> strategy, etc.).

You've learned your lessons well. That's fine. Now please understand
that there's a huge difference between the book (usually based on static
some static language) and dynamic OOPLs. IOW : free your mind.

In Python, you can dynamically change the class of an object at runtime.
And the attribute lookup rule is to first lookup the object, then the
class (which is itself an object FWIW). So you can see the object/class
relationship as a somewhat specialised composition/delegation
relationship. In fact, in Python, a class is both an object factory and
delegatee.

> You should google on "design patterns" and make your choice.

FWIW, a good part of the canonical design patterns are mostly workaround
the lack of flexibility in languages like C++ and Java. The Strategy
pattern's simplest Python implementation is to dynamically replace a
method on a per-object basis. The State pattern's simplest
implementation in Python is to dynamically change the class of an object.

Of course, one of the canonical solutions to the OP's problem is to use
composition/delegation. But doing it the canonical way would imply
creating instances of the role objects and passing them the instance as
param so they can access it's attributes. It works, but it creates a
cyclic dependancy between the object and it's roles, so you would have
to use weakrefs. Dynamically creating new classes with the appropriate
bases and assigning them to the object's __class__ attribute is another
way to achieve the same result, and it's perfectly legal.

Now I do agree that it can become tricky to manage correctly wrt/ mro
rules !-)



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Re: replace a method in class: how?

[Bruno Desthuilliers]

Maric Michaud wrote:
> Le mardi 27 juin 2006 06:21, Bruno Desthuilliers a écrit :
> 
>>Maric Michaud a écrit :
>>(snip)
>>
>>
>>>In OOP Methods are defined in *classes* not in any arbitrary object
>>
>>Chapter and verse, please ? AFAIK, the first O in OOP stands for
>>"object", not for "class" !-)
>>
> 
> Hard to find it, indeed.
> 
> 
>>Classes are just an implementation convenience, and the fact that the
>>class-based model is the most usual one doesn't imply it's the only
>>valid one.
> 
> Maybe, never been told of another one, do you think of javascript prototypes 
> ? 

There other prototype-based languages. And truth is that while having
classes, Python's object model is much more closer to javascript's one
than to Java or C++.

> Well, there are no methods in this model, only functions.

Nope. There are closures, not simple functions.

And FWIW, what do you think methods are in Python ? Yes, functions,
wrapped in a special descriptor.

> 
>>So there's no reason one shouldn't override (or add) a method 
>>on a per-object basis. As a matter of fact, it's perfectly legal (and
>>can be very convenient) to do so in Python.
> 
> I never saw the term "method" used for anything except for what it means for 
> classes,

Help on class instancemethod in module __builtin__:

class instancemethod(object)
 |  instancemethod(function, instance, class)
 |
 |  Create an instance method object.


> and moreover, the class model, even if it's just an implementation, 
> it's the one chosen by python.

There's a superficial similarity with "mainstream" static OOPLs like
Java/C++ etc. But Python's classes, and their relation to instances, are
as dynamic as can be, and really very different from what's in most books.

> For the common understanding of the model, IMHO, classes bind methods, 
> instances bind functions.

???

In Python, a class is nothing more than an object that:
1/ act as an object factory
2/ serves as delegatee for instances.

FWIW, the proper constructor (__new__, not __init__) is free to return
instances of any other class (as long as the initializer signature is
compatible).


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Re: Help with conversion VB script to Python : COM objects

[Roger Upole]

<[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED]
> Hi,
>
> I need to re-write a VB script into Python (because I really don't like
> VB).
>
> The VB script is used to create a Windows COM object.
> (I am more of Unix guy, so COM objects are a little bit alien for me).
>
> At a certain point in the VB script, I have the following line:
> objPolTypes = objPmad.Cvar(objPmad.GetPolicyTypeList)
>
> Does anybody what the equivalent in Python would be?
> I tried:
> objPolTypes = objPmad.Cvar(objPmad.GetPolicyTypeList() )
>
> but then I get the following error:
> "
> Traceback (most recent call last):
>  File "C:\Python24\MyProgs\FodFin\test.py", line 11, in ?
>objPolTypes = objPmad.cvar(objPmad.GetPolicyTypeList() )
>  File "", line 2, in cvar
> pywintypes.com_error: (-2147352571, 'Type mismatch.', None, 1)
> "
>
> I also tried :
> objPolTypes = objPmad.GetPolicyTypeList()
>
> this works but I end of with a list of COM object and have no clue how
> to query/use them or what methods are defined for those type of
> objects.
>
> Any help really appreciated.
>
> With kind regards,
>
> KRis
>

If the application has a typelib, you can use makepy to generate a wrapper
module that will show you the objects' methods and properties.
Otherwise, you'll have to depend on the documentation for the app.

   Roger




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Re: MSoffice metadata

[Roger Upole]

<[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED]
> hi
> is there a module in Python to extract metadata in MS office documents
> thanks
>

The Pywin32 package (http://sourceforge.net/projects/pywin32/)
wraps the interfaces used to read and write document properties.
Specifically, you can use pythoncom.StgOpenStorage to retrieve
an IPropertySetStorage interface.

 Roger





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Re: Replace Whole Object Through Object Method

[Bruno Desthuilliers]

I V wrote:
> On Mon, 26 Jun 2006 19:40:52 -0700, digitalorganics wrote:
> 
>>A misuse of inheritance eh? Inheritance, like other language features,
>>is merely a tool. I happen to be using this tool to have my virtual
>>persons change roles at different points in their lifetime, as many
>>real people tend to do. Thus, at these points, B is indeed an A. What a
>>person is, whether in real life or in my program, is not static and
>>comes into definition uniquely for each moment (micro-moment, etc.) of
>>existence. Now, please, I have no intention of carrying the
>>conversation in such a silly direction, I wasn't inviting a discussion
>>on philosophy or some such. I seek to work the tools to my needs, not
>>the other way around.
> 
> 
> But thinking about the problem in the vocabulary provided by the
> programming language can be helpful in coming up with a solution. If
> inheritance tells you what an object _is_,

It's not so clear in Python, cf my answer to Maric on this point.

> and membership tells you what a
> role _has_, and a role is something that a person has, 

As a matter of fact, in Python, the class is an attribute of an object.
So it is really something that an object "have". And this relationship
is not carved in stone - it's perfectly legal to modify it at runtime.

> that suggests
> that an implementation where roles are members of a person might be
> simpler than trying to use inheritance. Like, for instance:
> 
> class Role(object):
>   def __init__(self, person):
>   self.person = person
> 
(snip)
> 
> class Person(object):
> 
>   def __init__(self, name):
>   self.roles = []
>   self.name = name
> 
> 
>   def add_role(self, role_class):
>   self.roles.append(role_class(self))
> 

And here you create a circular reference between object and roles...


>   def forward_to_role(self, attr):
>   for role in self.roles:
>   try:
>   return getattr(role, attr)
>   except AttributeError:
>   pass
>   raise AttributeError(attr)

This could as well be directly in __getattr__, and would avoid a useless
method call.

>   
>   def __getattr__(self, attr):
>   self.forward_to_role(attr)
> 



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classes and interfaces

[s99999999s2003]

hi
i come from a non OO environment. now i am learning about classes. can
i ask, in JAva, there are things like interface. eg
public interface someinterface {
   public somemethod ();
   
   ...
}

In python , how to implement interface like the above? is it just
define a class??

class someinterface:
 def somemethod: blah

thanks

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Re: What is Expressiveness in a Computer Language

[Dr.Ruud]

Chris Smith schreef:

> So it seems to me that we have this ideal point at which it is
> possible to write all correct or interesting programs, and impossible
> to write buggy programs.

I think that is a misconception. Even at the idealest point it will be
possible (and easy) to write buggy programs. Gödel!

-- 
Affijn, Ruud

"Gewoon is een tijger."


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Re: Replace Whole Object Through Object Method

[Fredrik Lundh]

Bruno Desthuilliers wrote:

> As a matter of fact, in Python, the class is an attribute of an object.

except when it isn't.

>> def add_role(self, role_class):
>>self.roles.append(role_class(self))
>
> And here you create a circular reference between object and roles...

and ?  Python has a garbage collector, you know...

 



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Inconsistent float behaviour on "inf" - current state?

[Peter Knörrich]

Hello,

I've found another inconsistency, and looking through the
list archives I can find mentions of funky stuff like

print float('inf')

giving

Infanity

with Python 1.5.2 on Solaris 7 in 2001, and a couple closed bug
reports on why "float('inf')" isn't supported everywhere, and I
understand the underlying problem:

libc simply isn't that good - never mind standard - with regard to floats.

However, seeing how Python does a great job with long ints
by using something better than standard libc, I fail to see how
reliance on libc should be a reason not to provide at least consistency:

Why does conversion from a long constant not use the same
library function that conversion from a long string would use?

a = float(1234298299300)-> OverflowError: long int too large  
to convert to float
a = float('1234298299300')  -> inf, which led to silly errors in  
SQL (table has no column 'inf')

a = inf -> NameError: name 'inf' is not defined
a = float('inf')-> inf

Now, I could understand how that may need some changes on lexing
the source code, so I'm not actually opening more bugs having
found workarounds for my own troubles here (quality guys insisting
on entering silly numbers, hah, try that with a 50 character input
field limit!).

Still, I'm interested to hear what the current state of affairs is
on using possibly inconsistent libc for floats?

Bye,

Peter Knörrich

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Re: classes and interfaces

[Bruno Desthuilliers]

[EMAIL PROTECTED] wrote:
> hi
> i come from a non OO environment. now i am learning about classes. can
> i ask, in JAva, there are things like interface. eg
> public interface someinterface {
>public somemethod ();
>
>...
> }
> 
> In python , how to implement interface like the above? is it just
> define a class??

Java interfaces are a workaround the combination of static typing
(limiting polymorphism) and lack of multiple inheritance. Since Python
is dynamically typed (polymorphism does not depend on type), there's no
such need:

class Foo(object):
  def doThis(self):
print "in Foo.doThis"

class Bar(object):
  def doThis(self):
print "in Bar.doThis"

def doIt(obj):
  obj.doThis()

f = Foo()
b = Bar()

doIt(f)
doIt(b)

A you can see, doIt() works for any object having a doThis() method. No
need for inheritance or interface here.

Note that we do have something like interfaces (in some third-part
librairies), but with a somewhat different (and much more powerful) usage:

http://peak.telecommunity.com/protocol_ref/ref.html

But if you're new to OO, this may not be the best starting point !-)

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Re: Replace Whole Object Through Object Method

[Bruno Desthuilliers]

Fredrik Lundh wrote:
> Bruno Desthuilliers wrote:
> 
> 
>>As a matter of fact, in Python, the class is an attribute of an object.
> 
> 
> except when it isn't.

Which are the cases where it isn't ?

> 
>>>def add_role(self, role_class):
>>>   self.roles.append(role_class(self))
>>
>>And here you create a circular reference between object and roles...
> 
> 
> and ?  Python has a garbage collector, you know...

Yes. But garbage collection is not cost-free AFAIK.


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pyrex functions to replace a method (Re: replace a method in class: how?)

[Brian Blais]

Thanks for all who replied to this question about replacing a method.  I feel a 
little sheepish for not having caught that I have to replace it in the class, 
not the 
instance, but I have found a very similar problem trying to replace a method 
using a 
function defined in pyrex.   I post all of the code below, but there are 
several files.

The main code is:

import module_py   # import a function from a python module
import module_pyrex # import a function from a pyrex extension module

class This(object):

 def update1(self,val):
 print val

 def update2(self,val):
 print "2",val

 def update3(self,val):
 print "3",val

def local_update(obj,val):

 print "local",val


This.update1=local_update  # replace the method from a local function
This.update2=module_py.python_update  # replace the method from a python module
This.update3=module_pyrex.pyrex_update  # replace the method from a pyrex module

t=This()

t.update1('local')  # works fine
t.update2('python') # works fine
t.update3('pyrex')  # gives a typeerror function takes exactly 2 arguments (1 
given)
#-

#module_py.py

def python_update(self,val):
 print "python module",val
#-

#module_pyrex.pyx

def pyrex_update(self,val):
 print "pyrex module",val

#-


any ideas why the pyrex function fails?


thanks,


bb




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Modelica

[Srijit Kumar Bhadra]

I am looking for possible options to interface Modelica
(http://www.modelica.org/) with Python (scipy and numpy). Any
suggestions?

Best Regards,
Srijit

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RE: SWIG problems with gcc and Cygwin?

[Michael Yanowitz]

-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf
Of Steve Holden
Sent: Tuesday, June 27, 2006 2:55 AM
To: python-list@python.org
Subject: Re: SWIG problems with gcc and Cygwin?


Michael Yanowitz wrote:
>   No response yet. The SWIG test works fine in Linux no problems.
> However, I still have the problem in Cygwin.
>   Also, not sure if related but I do have a win32 Python 2.4.3 and
> Cygwin Python 2.4.1. Not sure if there are any conflicts. Any advice
> in making these two co-exist?
>   The only C/C++ compiler I have presently is Cygwin gcc.
>
I wouldn't claim to be an expert but it looks like you are missing
libraries. Shouldn't you at least be loading -l c to get functions
defined in libc?

regards
  Steve
--
Steve Holden   +44 150 684 7255  +1 800 494 3119
Holden Web LLC/Ltd  http://www.holdenweb.com
Love me, love my blog  http://holdenweb.blogspot.com
Recent Ramblings http://del.icio.us/steve.holden


   Possibly. I thought of that, but Linux doesn't require that I link in
the C Library. Maybe Cygwin does or maybe a parameter is needed in gcc
to do that automatically. The sample program (in
http://www.swig.org/tutorial.html )
does not mention this.

Thanks:
Michael Yanowitz

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Tkinter - Button Overrelief

[Fuzzyman]

Hello all,

I have some Tkinter buttons that display images. I would like to change
these to 'active' images when the mouse is over the button.

I see that the button widget can take an 'overrelief' argument in the
constructor. What values can this take ?

Also - can anyone provide an example of using the equivalent of a
'mouseover' event to change the image used by a button in Tkinter ? I'm
afraid google has not helped me much here.

Much Appreciated,


Fuzzyman
http://www.voidspace.org.uk/python/index.shtml

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Re: pyrex functions to replace a method (Re: replace a method in class: how?)

[Bruno Desthuilliers]

Brian Blais wrote:
> Thanks for all who replied to this question about replacing a method.  I
> feel a little sheepish for not having caught that I have to replace it
> in the class, not the instance, 

But you *can* replace it on a per-instance basis. It's easy, perfectly
legal, and can be very convenient.


I'm very sorry that some poster here try to forcefit Javaish restricted
OO conception into Python. Free your mind, burn your books, and take
full advantage of Python's powerfull object model.



> but I have found a very similar problem
> trying to replace a method using a function defined in pyrex.   I post
> all of the code below, but there are several files.
> 
> The main code is:
> 
> import module_py   # import a function from a python module
> import module_pyrex # import a function from a pyrex extension module
> 
> class This(object):
> 
> def update1(self,val):
> print val
> 
> def update2(self,val):
> print "2",val
> 
> def update3(self,val):
> print "3",val
> 
> def local_update(obj,val):
> 
> print "local",val
> 
> 
> This.update1=local_update  # replace the method from a local function
> This.update2=module_py.python_update  # replace the method from a python
> module
> This.update3=module_pyrex.pyrex_update  # replace the method from a
> pyrex module

Note that - from a purely technical POV - you don't need to define the
updateXXX methods in This. You can add methods directly - in fact,
defining a function in a class statement will end up doing the same
thing as binding it to the class objet outside the class statement.

> t=This()
> 
> t.update1('local')  # works fine
> t.update2('python') # works fine
> t.update3('pyrex')  # gives a typeerror function takes exactly 2
> arguments (1 given)

(snip)
> 
> any ideas why the pyrex function fails?
> 

I don't have much knowledge wrt/ pyrex, but I guess that pyrex functions
don't implement the descriptor protocol as pure Python functions do, so
the instance object is not passed to the function at calltime.


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Re: How do you use this list ?

[Claudio Grondi]

Bo Yang wrote:
> Hi everyone ,
> I have join this list for about 4 months , and everyday I receive
> hundreds of
> mails . There is no means to read all of them , so I just read something
> interesting
> for me . But if so , there are too much mails pile up in my inbox , I
> want to ask
> how do you use this list , reading every mail come in or just read what
> you think
> interesting ?
> 
> Thank you !
> 
> 
> Best Regard !

I am using a newsreader capable of showing posting in their threads in a
hierarchical view.
I read entire messages only if I mean the topic is of interest to me, if
I have spotted something interesting in the first lines of a posting or
if I mean, that I can immediately help writing a reply without much
efforts on my side what is the case when the answer pops up in my mind
already as I see the question.
It was the topic "How do you use this list?" what attracted my attention
so I looked into the content of your posting and decided to reply.
My advice: download e.g. Thunderbird and use it as a newsreader instead
of getting through not by thread and date structured piles of emails.
I actually go through each single posting spending at least a second on
each (sometimes a bit faster, sometimes much slower).
This gives an effort of about 10 minutes of very concentrated work
towards selection of interesting postings for detailed reading on a day
with a huge traffic of around 600 new postings.
Over years of reading I improved much the speed of perception at first
glance if a posting or a thread is in my eyes worth to read it in
detail. As I also in between know who writes here the best quality
replies I usually read carefully all the details in postings of such
authors skipping from reading another postings in same thread.

Hope this helps.

Claudio
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Re: Python is fun (useless social thread) ;-)

[Bruno Desthuilliers]

BartlebyScrivener wrote:
>>You know what are dicts, right ? That is, containers with keyword-access
>>to values ? Then you probably have dicts with a known, defined
>>structure, and functions working on it. What classes (and hence 00)
>>gives you is a way to associate these functions with the dicts
>>themselves. That is the big intuition about objects, the rest is just
>>details.
> 
> 
> Bruno,
> 
> Ever seen this from Fuzzyman? It explicitly uses the dict comparison.
> 
> http://www.voidspace.org.uk/python/articles/OOP.shtml#introduction

Nope - and the site seems to be down actually. But thanks for the
pointer anyway.

> Thanks for the tip,

Welcome to OO !-)

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p in '[EMAIL PROTECTED]'.split('@')])"
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how to do -vv for very verbose?

[Hari Sekhon]

I'm using optparse.Optionparser to take switches for a script I'm 
writing, but I can't see how to give it -vv for very verbose.

the option for -v is simply set to True by the option parser if present, 
whereas I really want a numeric value, 1 if there is -v and 2 if there 
is -vv.

Any ideas on how to do this?

I think I'll have to stop using  action="store_true".

-h
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Re: classes and interfaces

[Paul McGuire]

<[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> hi
> i come from a non OO environment. now i am learning about classes. can
> i ask, in JAva, there are things like interface. eg
> public interface someinterface {
>public somemethod ();
>
>...
> }
>
> In python , how to implement interface like the above? is it just
> define a class??
>
> class someinterface:
>  def somemethod: blah
>
> thanks
>

This question crops up every week or two on this list.  (This is a healthy
indicator of people looking to map their Java learnings to Python.  Some of
the best programming knowledge I've gained has come from comparing features
among different languages, and understanding their respective
purposes/strengths/shortcomings.  In this case, presence of interfaces in
Java)  Here are some recent threads that cover this topic:

http://groups.google.com/group/comp.lang.python/browse_frm/thread/d5da229b0050725d/47411c8c9322821c?q=java+interface&rnum=20#47411c8c9322821c

http://groups.google.com/group/comp.lang.python/browse_frm/thread/d5da229b0050725d/47411c8c9322821c?q=java+interface&rnum=20#47411c8c9322821c


Is this in the FAQ?  Hmm, these two FAQ's may be related to your question
(although you have to know what you're looking for to recognize them):
http://www.python.org/doc/faq/general/#how-do-you-specify-and-enforce-an-interface-spec-in-python
http://www.python.org/doc/faq/programming/#is-there-a-tool-to-help-find-bugs-or-perform-static-analysis


Lastly, you should look into


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Re: style question

[Hari Sekhon]

Claudio Grondi wrote:
> Hari Sekhon wrote:
>> On 26/06/06, *Claudio Grondi* <[EMAIL PROTECTED] 
>> > wrote:
>>
>> Scott David Daniels wrote:
>>  > Claudio Grondi wrote:
>>  > <<>>
>>  >
>>  >> When necessary to skip first line _and_ indentation:
>>  >>   message = """
>>  >>   This is line 1
>>  >>   This is line 2
>>  >>   This is line 3
>>  >>   """.replace('\n  ', '\n')[1:] # adjust here '\n  ' to 
>> indentation
>>  >
>>  >
>>  > Riffing on this idea:
>>  > message = """
>>  >   This is line 1
>>  >   This is line 2
>>  >   This is line 3
>>  >   """.replace("""
>>  >   """, '\n')[1:]
>>
>> This was intended as an excercise for the OP in case he likes 
>> that kind
>> of solution ...
>>
>> Claudio
>>
>>  >
>>  > --Scott David Daniels
>>  > [EMAIL PROTECTED] 
>> --
>> http://mail.python.org/mailman/listinfo/python-list
>>
>>
>> I've decided to go with
>>
>>message = (
>>"This is line1. "
>>"This is line2 "
>>"This is line3\n")
>>
>> since I'm declaring many different messages inside various functions 
>> I feel it is important to keep the indentaion and code both aligned 
>> properly so the code looks nice and the output looks nice.
>>
>> It is easier than doing replace and splicing since I want to keep it 
>> as simple and clean as possible, in true pythonic tradition...
>>
>> Thanks for the input!
>>
>> -h
>>
> Thanks for the reply and the explanation what you finally decided to 
> go with.
> I am so happy to have the triple quotes in Python, that I use them 
> whenever possible - this has probably something to do with my bias 
> towards plain text files with human readable content, so as 
> readability is very important to me (and probably to many other 
> Pythonistas) I like most the proposed by me triple quote style as the 
> quotation marks in the style you prefer make the text of the 'message' 
> less easy to read.
>
> Now we can start a flame war about which style is more 'pythonic' ;-)
>
> Claudio
>
I already explained that the triple quotes don't work tidily with 
indentation, either the code is out of alignment or the printout is. 
Either way isn't good.
Triple quotes are best at top level, but since I had to use many 
messages inside functions etc, they broke the layout of the code.

I think they're both best depending on where you are putting them. I'm 
doing very custom messages for each different result, so it would be 
messy to do this at the top level.

-h

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Re: how to do -vv for very verbose?

[Fredrik Lundh]

Hari Sekhon wrote:

> I'm using optparse.Optionparser to take switches for a script I'm
> writing, but I can't see how to give it -vv for very verbose.
>
> the option for -v is simply set to True by the option parser if present,
> whereas I really want a numeric value, 1 if there is -v and 2 if there
> is -vv.

action="count" ?

 



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Re: how to do -vv for very verbose?

[Hari Sekhon]

Fredrik Lundh wrote:

  Hari Sekhon wrote:

  
  
I'm using optparse.Optionparser to take switches for a script I'm
writing, but I can't see how to give it -vv for very verbose.

the option for -v is simply set to True by the option parser if present,
whereas I really want a numeric value, 1 if there is -v and 2 if there
is -vv.

  
  
action="" ?

 



  

yeah, I realised this just after I sent it, sort it out.

Thanks.


-h


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Re: classes and interfaces

[Paul McGuire]

"Paul McGuire" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
>
> Lastly, you should look into
>

... this blog post:  http://dirtsimple.org/2004/12/python-is-not-java.html,
and its partner http://dirtsimple.org/2004/12/python-is-not-java.html.

Unfortunately, many who ask "How do I implement a Java interface in Python?"
are met with some defensiveness on this list, as if the OP is asking "What's
wrong with stupid Python language that it doesn't have something as basic as
interfaces?".  Sometimes this is attitude on the OP's part, sometimes just
presumption on the part of the various readers.  Some responses are of an
indignant "Interfaces? We don't need no stinkin' interfaces!" variety -
unfortunately, most of these shed more heat than light to the discussion,
usually omitting the important details as to *why* Python don't need those
malodorous code devices.

Java uses interfaces for two purposes:
1. to enforce at compile time whether a particular class implements a set of
methods, and correspondingly enforce that only instances of such classes are
permitted as arguments to functions/methods that declare arguments to be of
the interface type
2. as a workaround for not directly supporting multiple inheritance

Informally (and in design practices such as UML class diagrams), interfaces
also serve to document expected class capabilities - which in the case of
Java and C++, have the added support of compile-time checking to verify the
class contains methods corresponding to those in the interface.  Note that
I've been careful *not* to imply that Java classes that pass this
compile-time check actually *implement* the interface, as is often assumed.
The only thing one knows for sure when Java accepts a class as being an
interface implementer is that the class provides all the corresponding
method definitions - but it cannot know if all expectations of behavior and
pre- and post-conditions are actually implemented within those methods.
While compile-time checking is a decent crutch 95% of the time, it will
never catch errors like this:

int passBackSomethingImportant() {
// be sure to come back and implement this before production
release!
return 0;
}

Very few "how do I implement Java interfaces in Python" posters ever get
specific about which purpose they are trying to address with their Python
interface renditions.  It is entirely possible that the posters don't *know*
why the interface is there, they are just trying to directly port some Java
code to Python.

So specifically:
1. Python does not do any compile-time enforcement of method implementations
in classes of objects.  While some think this is like trapeze flying without
a net, Pythoneers will reply that the net is a false assurance anyway (based
on the example I show above).  So to "port" this type of interface, the only
thing to do is, well, ignore the interface - Python really doesn't require
it.  You *could* create a class such as:

class ISomethingOrOther:
   def whatSomethingsDo(blah, blah2):
   raise NotImplementedError, "derived class failed to implement
'whatSomethingsDo' method"

and then have target classes include ISomethingOrOther in their base class
lists.  But Python does not do any compile-time enforcement with these
definitions.  You *still* have to do runtime testing to see if the
NotImplemented exceptions get thrown.

2. Python supports multiple inheritance without the indirection of
interfaces, so you can just inherit implementation classes directly:

class Swimmer:
  def swim():
 pass

class Flyer:
  def fly():
  pass

class Duck(Swimmer,Flyer):
   pass

and merrily write:

dd = Duck()
dd.fly()
dd.swim()


Sorry for the long discourse, I didn't have time to make it shorter.

HTH,
-- Paul


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Re-loading updated modules

[fileexit]

Hi,
Shouldn't python recompile a module if there is a later version of the
code (.py file)? While i am debuging, i always have to exit python and
delete the pyc before every run, then start it again and import the
modules.  It seems that this is the only way for it to recompile the
new code.

What is going on? is this normal behaviour? I noticed that on both
Windows and linux (Fedora Core 4, and 5 and RHEL 4)

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"no module named win32api" using PyWin32-208

[Mike]

Hi.

I have Python 2.4 installed on my local machine in c:\Python24. I have
also downloaded the python for windows extensions installer
pywin32-208.win32-py2.4.exe and installed this to
C:\Python24\Lib\site-packages

Trying to run a python script through a C# console app is causing me
problems: the last line of code in the following block results in a no
module named win32ap error. I'm not sure if this is because there is no
win32api.py in the win32 fikder off site-packages, just a win32api.pyc
file.

m_engine = new PythonEngine();

m_engine.AddToPath("C:\\Python24\\DLLs");
m_engine.AddToPath("C:\\Python24\\lib");
m_engine.AddToPath("C:\\Python24\\lib\\plat-win");
m_engine.AddToPath("C:\\Python24\\lib\\lib-tk");

m_engine.AddToPath("C:\\Python24\\Lib\\site-packages\\pythonwin");
m_engine.AddToPath("C:\\Python24");
m_engine.AddToPath("C:\\Python24\\lib\\site-packages");

m_engine.AddToPath("C:\\Python24\\lib\\site-packages\\win32");

m_engine.AddToPath("C:\\Python24\\lib\\site-packages\\win32\\lib");

m_engine.Execute("from win32api import win32api");

I have added all the addtopaths to get the path to match the sys.path I
see in a normal python console which can successfully import the
module.

Incidentally, I have tried making the last line
 m_engine.Execute("import win32api");
with no luck.

Can the win32 extensions handle compiled python modules? If not how can
I get it to work?

Thanks,
Mike

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Re: How do you use this list ?

[Michele Simionato]

Bo Yang wrote:
> Hi everyone ,
> I have join this list for about 4 months , and everyday I receive
> hundreds of
> mails . There is no means to read all of them , so I just read something
> interesting
> for me . But if so , there are too much mails pile up in my inbox , I
> want to ask
> how do you use this list , reading every mail come in or just read what
> you think
> interesting ?
>
> Thank you !
>
>
> Best Regard !

I use the newsgroup: http://groups.google.com/group/comp.lang.python

 Michele Simionato

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Re: Having problems with strings in HTML

[Sion Arrowsmith]

Lawrence D'Oliveiro  <[EMAIL PROTECTED]> wrote:
> Kiana Toufighi <[EMAIL PROTECTED]> wrote:
>
>>print '''
>>>href="http://bbc.botany.utoronto.ca/ntools/cgi-bin/ntools_treeview_word.cgi?inp
>>ut=&max=2&values_off=no&remove_bracket=no&show_line_nr=yes&show_link_out=yes
>> [ ... ] ">GraphicalOutput
>> ''' [ ... ]
>
>By the way, you _do_ realize that your "&" characters should be escaped 
>as "&", don't you?

No they shouldn't. They part of the url, which is (IIRC) a CDATA
attribute of the A element, not PCDATA.

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  ___  |  "Frankly I have no feelings towards penguins one way or the other"
  \X/  |-- Arthur C. Clarke
   her nu becomeþ se bera eadward ofdun hlæddre heafdes bæce bump bump bump
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Re: Re-loading updated modules

[Pierre Quentel]

Instead of exiting the interpreter, you can use reload() : see the
section "Built-in functions" in the library reference

"reload( module)
Reload a previously imported module. The argument must be a module
object, so it must have been successfully imported before. This is
useful if you have edited the module source file using an external
editor and want to try out the new version without leaving the Python
interpreter. The return value is the module object (the same as the
module argument). "

Pierre

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Re: Re-loading updated modules

[Fredrik Lundh]

"fileexit" <[EMAIL PROTECTED]> wrote:

> Shouldn't python recompile a module if there is a later version of the
> code (.py file)?

it does, when the module is first loaded.

> While i am debuging, i always have to exit python and
> delete the pyc before every run

deleting the PYC shouldn't be necessary.

> then start it again and import the
> modules.  It seems that this is the only way for it to recompile the
> new code.

reload(module)

however, see the caveats on this page:

http://pyref.infogami.com/reload

> What is going on? is this normal behaviour?

yes.  and this is tutorial stuff, too:

http://pytut.infogami.com/node8.html

 



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Re: Re-loading updated modules

[Paul McGuire]

"fileexit" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Hi,
> Shouldn't python recompile a module if there is a later version of the
> code (.py file)? While i am debuging, i always have to exit python and
> delete the pyc before every run, then start it again and import the
> modules.  It seems that this is the only way for it to recompile the
> new code.
>
> What is going on? is this normal behaviour? I noticed that on both
> Windows and linux (Fedora Core 4, and 5 and RHEL 4)
>
If there is a later .py file, and you restart Python, Python will recompile
the modules when you import them.

-- Paul



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using pydoc in an application

[timw.google]

Hi all,

I'm discovering pydoc, and it seems to me that this is a great way to
have online documentation for my application. Are there any examples of
using this in some kind of help menu in an application?  I've tried to
just bind pydoc.gui() to a menu item, but this just brings up the GUI
for pydoc, and the user still needs to search for the module before the
browser comes up, and when I quit serving pydoc.gui(), my application
dies along with it. Also, I need to get out of python to use pydoc.gui
again, or I get

error: (98, 'Address already in use')

I'm sure there's a better way to take advantage of this module and my
docstrings to get some online help.  I'm using Tkinter and Pmw, but
maybe it's time to convert all this to wxWidgets?

Thanks for any help.

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Re: Tkinter - Button Overrelief

[Eric Brunel]

On Tue, 27 Jun 2006 14:06:05 +0200, Fuzzyman <[EMAIL PROTECTED]> wrote:

> Hello all,
>
> I have some Tkinter buttons that display images. I would like to change
> these to 'active' images when the mouse is over the button.
>
> I see that the button widget can take an 'overrelief' argument in the
> constructor. What values can this take ?

The same as the 'relief' option, i.e the ones described here:
http://www.tcl.tk/man/tcl8.4/TkCmd/options.htm#M-relief

Note that Tkinter contains symbolic constants for these values: 'raised'  
is Tkinter.RAISED, 'flat' is Tkinter.FLAT, and so on.

> Also - can anyone provide an example of using the equivalent of a
> 'mouseover' event to change the image used by a button in Tkinter ? I'm
> afraid google has not helped me much here.

The events you're after are '' and ''; see here:
http://www.tcl.tk/man/tcl8.3/TkCmd/bind.htm#M7

Here is an example showing how to change the button text (changing the  
image is similar):


 from Tkinter import *

root = Tk()

b = Button(root, width=8, text='foo')
b.pack()

def enterB(event):
   b.configure(text='bar')

def leaveB(event):
   b.configure(text='foo')

b.bind('', enterB)
b.bind('', leaveB)

root.mainloop()


HTH
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Re: Having problems with strings in HTML

[Fredrik Lundh]

Sion Arrowsmith wrote:

>>By the way, you _do_ realize that your "&" characters should be escaped
>>as "&", don't you?
>
> No they shouldn't. They part of the url, which is (IIRC) a CDATA
> attribute of the A element, not PCDATA.

Yes they should.  CDATA sections can contain character entities; it's elements
that are ignored, not character/entity references.

 



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Re: What is Expressiveness in a Computer Language

[David Hopwood]

Marshall wrote:
> The real question is, are there some programs that we
> can't write *at all* in a statically typed language, because
> they'll *never* be typable?

In a statically typed language that has a "dynamic" type, all
dynamically typed programs are straightforwardly expressible.

In a statically typed, Turing-complete language that does not have a
"dynamic" type, it is always *possible* to express a dynamically typed
program, but this may require a global transformation of the program
or use of an interpreter -- i.e. the "Felleisen expressiveness" of the
language is reduced.

-- 
David Hopwood <[EMAIL PROTECTED]>
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Re: Having problems with strings in HTML

[Richard Brodie]

"Sion Arrowsmith" <[EMAIL PROTECTED]> wrote in message 
news:[EMAIL PROTECTED]

>>By the way, you _do_ realize that your "&" characters should be escaped
>>as "&", don't you?
>
> No they shouldn't. They part of the url, which is (IIRC) a CDATA
> attribute of the A element, not PCDATA.

It is CDATA but ampersands still need to be escaped. 


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Re: How do you use this list ?

[Marius Ursache]

Bo Yang wrote:
> Hi everyone ,
> I have join this list for about 4 months , and everyday I receive
> hundreds of
> mails . There is no means to read all of them , so I just read something
> interesting
> for me . But if so , there are too much mails pile up in my inbox , I
> want to ask
> how do you use this list , reading every mail come in or just read what
> you think
> interesting ?
>

I use digest messages on a gmail account. i read the digests whenever i
have time.

--
M.

http://marius.me.uk/

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Re: How do you use this list ?

[Grant Edwards]

On 2006-06-27, Bo Yang <[EMAIL PROTECTED]> wrote:

> I have join this list for about 4 months , and everyday I
> receive hundreds of mails . There is no means to read all of
> them , so I just read something interesting for me . But if so
> , there are too much mails pile up in my inbox , I want to ask
> how do you use this list , reading every mail come in or just
> read what you think interesting ?

Find an NNTP server and read it as a newsgroup.  

If all else fails you can read it via gmane.org.

Actually having mailing lists send you mail is insane.

-- 
Grant Edwards   grante Yow!  I wonder if I ought
  at   to tell them about my
   visi.comPREVIOUS LIFE as a COMPLETE
   STRANGER?
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Unbound Local error? How?

[Hari Sekhon]

I've got some code as follows:

import re
re_regexname = re.compile('abc')

.
. various function defs
.

def func1():
...
func2()
...

def func2():
if re_regexname.match('abc'):
   

if __name__ == '__main__':
func1()


but this returns the Traceback:

UnboundLocalError: local variable 're_regexname' referenced before 
assignment


How?

It was declared in the zero level indentation near the top of the 
script! I don't understand this, isn't a function supposed to be able to 
reference stuff in the containing function or the top level?
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Re: Unbound Local error? How?

[Diez B. Roggisch]

Hari Sekhon wrote:

> import re
> re_regexname = re.compile('abc')
> 
> .
> . various function defs
> .
> 
> def func1():
> ...
> func2()
> ...
> 
> def func2():
> if re_regexname.match('abc'):
> 
> 
> if __name__ == '__main__':
> func1()


The above clearly is not what you have. See the attached version of the
above that works. So - go check for a typo or something like that.

Diezimport re
re_regexname = re.compile('abc')

def func1():
func2()

def func2():
if re_regexname.match('abc'):
print " whohoo!"

if __name__ == '__main__':
func1()
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Re: Unbound Local error? How?

[Hari Sekhon]

Diez B. Roggisch wrote:

  Hari Sekhon wrote:

  
  
import re
re_regexname = re.compile('abc')

.
. various function defs
.

def func1():
...
func2()
...

def func2():
if re_regexname.match('abc'):


if __name__ == '__main__':
func1()

  
  

The above clearly is not what you have. See the attached version of the
above that works. So - go check for a typo or something like that.

Diez
  

import re
re_regexname = re.compile('abc')

def func1():
func2()

def func2():
if re_regexname.match('abc'):
print " whohoo!"

if __name__ == '__main__':
func1()
  

you're right, it wasn't that, I was trying to locally override a regex
object as follows:

re_somepattern = re.compile('abc')
re_someotherpattern = re.compile('def')

def func():
    if somecondition:
        re_somepattern = re_someotherpattern

    
        re_somepattern.match('something')
    

not sure how to override this the way I want, it'd be quite messy if I
had to do huge if blocks to handle this inside the other code blocks
that use this re_somepattern.match()

or perhaps I'm going about this all wrong

-h



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Re: How do you use this list?

[Klaus Alexander Seistrup]

Grant Edwards wrote:

> Find an NNTP server and read it as a newsgroup.  

Or Google Groups: http://groups.google.com/group/comp.lang.python

Cheers,

-- 
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Dyssegård, Denmark
http://surdej.dk/
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Re: Is Queue.Queue.queue.clear() thread-safe?

[Russell Warren]

Thanks guys.  This has helped decipher a bit of the Queue mechanics for
me.

Regarding my initial clear method hopes... to be safe, I've
re-organized some things to make this a little easier for me.  I will
still need to clear out junk from the Queue, but I've switched it so
that least I can stop the accumulation of new data in the Queue while
I'm clearing it.  ie: I can just loop on .get until it is empty without
fear of a race, rather than needing a single atomic clear.

My next Queue fun is to maybe provide the ability to stuff things back
on the queue that were previously popped, although I'll probably try
and avoid this, too (maybe with a secondary "oops" buffer).

If curious why I want stuff like this, I've got a case where I'm
collecting data that is being asynchronously streamed in from a piece
of hardware.  Queue is nice because I can just have a collector thread
running and stuffing the Queue while other processing happens on a
different thread.  The incoming data *should* have start and stop
indications within the stream to define segments in the stream, but
stream/timing irregularities can sometimes either cause junk, or cause
you to want to rewind the extraction a bit (eg: in mid stream-assembly
you might realize that a stop condition was missed, but can deduce
where it should have been).  Fun.

Russ

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Re: What is Expressiveness in a Computer Language

[Marshall]

Ketil Malde wrote:
> "Marshall" <[EMAIL PROTECTED]> writes:
>
> > There are also what I call "packaging" issues, such as
> > being able to run partly-wrong programs on purpose so
> > that one would have the opportunity to do runtime analysis
> > without having to, say, implement parts of some interface
> > that one isn't interested in testing yet. These could also
> > be solved in a statically typed language. (Although
> > historically it hasn't been done that way.)
>
> I keep hearing this, but I guess I fail to understand it.  How
> "partly-wrong" do you require the program to be?
>
> During development, I frequently sprinkle my (Haskell) program with
> 'undefined' and 'error "implement later"' - which then lets me run the
> implemented parts until execution hits one of the 'undefined's.
>
> The "cost" of static typing for running an incomplete program is thus
> simply that I have to name entities I refer to.  I'd argue that this
> is good practice anyway, since it's easy to see what remains to be
> done. (Python doesn't seem to, but presumably a serious dynamically
> typed system would warn about references to entities not in scope?)

I'll give you my understanding of it, but bear in mind that I only
program
in statically typed languages, and I in fact do exactly what you
decribe
above: stub out unimplemented methods.

The issue is that, while stubbing out things may not be expensive,
it is not free either. There is some mental switching cost to being
in a state where one writes some code, wants to execute it, but
can't, because of type system constraints that are globally applicable
but not locally applicable to the task at hand, or to the specific
subprogram one is working on right at that moment.

Since I'm very used to doing it, it doesn't seem like an issue to
me, but programmers in dynamical languages complain bitterly
about this. It is my feeling that programming languages should
try to be inclusive, and since this feature is easily enough
accomodated, (as a 'lenient' switch to execution) it ought
to be.


Marshall

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Re: How do you use this list?

[Grant Edwards]

On 2006-06-27, Klaus Alexander Seistrup <[EMAIL PROTECTED]> wrote:
> Grant Edwards wrote:
>
>> Find an NNTP server and read it as a newsgroup.  
>
> Or Google Groups: http://groups.google.com/group/comp.lang.python

I did heard a rumor that they finally fixed the "follow-up"
function that had been broken since day 1.  Still, it does a
bad reputation similar to AOL used to...

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Re: What is Expressiveness in a Computer Language

[Marshall]

David Hopwood wrote:
> Marshall wrote:
> > The real question is, are there some programs that we
> > can't write *at all* in a statically typed language, because
> > they'll *never* be typable?
>
> In a statically typed language that has a "dynamic" type, all
> dynamically typed programs are straightforwardly expressible.

So, how does this "dynamic" type work? It can't simply be
the "any" type, because that type has no/few functions defined
on it. It strikes me that *when* exactly binding happens will
matter. In a statically typed language, it may be that all
binding occurs at compile time, and in a dynamic language,
it may be that all binding occurs at runtime. So you might
have to change the binding mechanism as well. Does the
"dynamic" type allow this?

 
Marshall

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Re: Having problems with strings in HTML

[Walter Dörwald]

Richard Brodie wrote:
> "Sion Arrowsmith" <[EMAIL PROTECTED]> wrote in message 
> news:[EMAIL PROTECTED]
> 
>>> By the way, you _do_ realize that your "&" characters should be escaped
>>> as "&", don't you?
>> No they shouldn't. They part of the url, which is (IIRC) a CDATA
>> attribute of the A element, not PCDATA.
> 
> It is CDATA but ampersands still need to be escaped. 

Exactly. See
http://www.w3.org/TR/html4/appendix/notes.html#ampersands-in-uris

Bye,
   Walter Dörwald
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Re: Having problems with strings in HTML

[Richie Hindle]

[Kiana]
> http://bbc.botany.utoronto.ca/[...]?input=&max=2[...]";>

[Lawrence]
> By the way, you _do_ realize that your "&" characters should be escaped 
> as "&", don't you?

[Sion]
> No they shouldn't. They part of the url, which is (IIRC) a CDATA
> attribute of the A element, not PCDATA.

The W3C validator at http://validator.w3.org/ disagrees with you.  It
accepts this:

http://www.w3.org/TR/html4/strict.dtd";>
Test

http://somewhere.com?a=1&b=2";>link


but rejects this:

http://www.w3.org/TR/html4/strict.dtd";>
Test

http://somewhere.com?a=1&b=2";>link


saying "cannot generate system identifier for general entity "b" [...] The
most common cause of this error is unencoded ampersands in URLs".

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[W2k, wxPython 2.6.1.0] - MDISashDemo bug?

[w.p.]

When i run MDISashDemo and maximize main frame, minimize and maximize 
again - LayoutMDIFrame in OnSize dont work more...
Why?

I need this feature for main MDI frame with toolbar and statusbar with 
panels&sizers&bitmapbuttons :)

Windows 2000, wxPython 2.6.1.0

w.p.

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Re: Unbound Local error? How?

[Bruno Desthuilliers]

Hari Sekhon wrote:
> I've got some code as follows:
> 
> import re
> re_regexname = re.compile('abc')
> 
> .
> . various function defs
> .
> 
> def func1():
>...
>func2()
>...
> 
> def func2():
>if re_regexname.match('abc'):
>   
> 
> if __name__ == '__main__':
>func1()
> 
> 
> but this returns the Traceback:
> 
> UnboundLocalError: local variable 're_regexname' referenced before
> assignment

this is *not* the traceback. This is only the error message. The
traceback contains all needed informations (or at least all possible
information at this point) to know what happened. But you did not post
the traceback. Nor did you post the minimal runnable code snippet
producing this error.

> 
> How?

How could we know ?


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Re: Unbound Local error? How?

[Hari Sekhon]

Bruno Desthuilliers wrote:

  Hari Sekhon wrote:
  
  
I've got some code as follows:

import re
re_regexname = re.compile('abc')

.
. various function defs
.

def func1():
   ...
   func2()
   ...

def func2():
   if re_regexname.match('abc'):
  

if __name__ == '__main__':
   func1()


but this returns the Traceback:

UnboundLocalError: local variable 're_regexname' referenced before
assignment

  
  
this is *not* the traceback. This is only the error message. The
traceback contains all needed informations (or at least all possible
information at this point) to know what happened. But you did not post
the traceback. Nor did you post the minimal runnable code snippet
producing this error.

  
  
How?

  
  
How could we know ?


  


sorry, I know it looks like I was being stingy but the traceback was
not that helpful, not without seeing more a huge amount more of the
code. I was trying to abbreviate.

Traceback (most recent call last):
  File "./backup.py", line 649, in ?
    backup(machine,share)
  File "./backup.py", line 364, in backup
    backupdir(source,destination)
  File "./backup.py", line 398, in backupdir
    (dirlist,filelist) = getdirlisting( source )
  File "./backup.py", line 445, in getdirlisting
    if re_skip_dirs.match(x):
UnboundLocalError: local variable 're_skip_dirs' referenced before
assignment

This doesn't really show that much, I figured the problem was the
following:

def getdirlisting():
     re_skip_dirs = re_skip_top_dirs   #Here's the culprit

where both these regex compiled objects were declared at the top level,
it seems that the assignment is trying to use the local variable
re_skip_top_dirs which doesn't exist, that's why I'm getting a
traceback, commenting out this line it runs fine.

-h




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Re: [Stackless] Suggestion for a Solution ? Re: Blocking Problem with Stackless Python and Twisted

[Patrick M. Nielsen]

I had a similar problem, and Radix's threadless Twisted snippet proved to be a very viable solutionHave a look at: http://twistedmatrix.com/trac/browser/sandbox/radix/threadless.py?rev=17407
On 6/26/06, Andrew Francis <[EMAIL PROTECTED]> wrote:
Hello Jas, Bob, et al:> Twisted isn't designed for Stackless integration,> and the approach  you're taking simply will notwork.> Twisted does block on reactor.run(), and during> each runloop iteration it blocks waiting for a
>timeout or network activity (via  select or poll>usually).~> What's the deal with this error from> stackless.run():...>have some reasons to need to be able to run a
>scheduler on another thread... Did someone discover>some problem? Or is this check just overly>conservative? (A few simple scheduling experiments>seem to run without problem...)>From what I can tell, the only time I really care
about blocking that cuts down overall concurrency iswhen I have tasklets running in parallel, and one ormore of those tasklets, at some low level will bedoing an IO operation that can block for anindeterminate amount of time (
i.e., an accept()).That said, I beleive the the easiest way to get aroundthis problem is to bite the bullet and run Twisted (orthe programme with blocking IO) in another process.In turn, I :
1. create a simple protocol.2. and have my Stackless process establish aconnection with the process doing the actual IO (someother IPC could also be used).3. Mark the socket as non-blocking (or use MSG_PEEK?)
4. Have tasklets with a network event loop.#requestswhile (some_condition): request = requestChannel.receive() serverSocket.send(request) stackless.schedule()#responses
while (some_condition): if (there is data): reply = serverSocket.receive() replyChannel.send(reply) stackless.schedule()you get the idea. Comments? Suggestions?
Cheers,Andrew__Do You Yahoo!?Tired of spam?  Yahoo! Mail has the best spam protection aroundhttp://mail.yahoo.com
___Stackless mailing list[EMAIL PROTECTED]
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Re: What is Expressiveness in a Computer Language

[George Neuner]

On Mon, 26 Jun 2006 13:02:33 -0600, Chris Smith <[EMAIL PROTECTED]>
wrote:

>George Neuner  wrote:
>
>> I worked in signal and image processing for many years and those are
>> places where narrowing conversions are used all the time - in the form
>> of floating point calculations reduced to integer to value samples or
>> pixels, or to value or index lookup tables.  Often the same
>> calculation needs to be done for several different purposes.
>
>These are value conversions, not type conversions.  Basically, when you 
>convert a floating point number to an integer, you are not simply 
>promising the compiler something about the type; you are actually asking 
>the compiler to convert one value to another -- i.e., see to it that 
>whatever this is now, it /becomes/ an integer by the time we're done.  
>This also results in a type conversion, but you've just converted the 
>value to the appropriate form.  There is a narrowing value conversion, 
>but the type conversion is perfectly safe.

We're talking at cross purposes.  I'm questioning whether a strong
type system can be completely static as some people here seem to
think.  I maintain that it is simply not possible to make compile time
guarantees about *all* runtime behavior and that, in particular,
narrowing conversions will _always_ require runtime checking.


>> I can know that my conversion of floating point to integer is going to
>> produce a value within a certain range ... but, in general, the
>> compiler can't determine what that range will be.
>
>If you mean "my compiler can't", then this is probably the case.  If you 
>mean "no possible compiler could", then I'm not sure this is really very 
>likely at all.

Again, the discussion is about narrowing the result.  It doesn't
matter how much the compiler knows about the ranges.  When the
computation mixes types, the range of the result can only widen as the
compiler determines the types involved.

George
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How to disable tk inclusion in py build

[venkatbo]

Hi folks,

I'd like to disable the inclusion of tk graphics lib in my py build.
Looked around but couldn't find a clear answer. Which one of
the following would I need to use in the configure step:
  --disable-tkbuild
  --without-tk

Thanks,
/venkat

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Re: What technologies should I use for my application manager?

[Adam Jones]

MrBlueSky wrote:
> Thanks for the advice, Adam!
>
> Turbogears sounds like it does everything I want and looks like a
> great...  except you've made me nervous with your comment on the
> instability of the Oracle API!

It is not impossible to find a stable ORM for access to Oracle, just
slightly more difficult. Both of the systems in question are working on
perfecting the currently experimental support.

>
> Stability, good documentation and a wide user base are priorities.  I
> was delighted by the quality of Tkinter in this regard.  Am I wishing
> for the moon in hoping for the same quality in the framework I choose
> for this?
> 
> Anyone else like to try and sell me on Zope or Django?!

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Re: Python is fun (useless social thread) ;-)

[John Salerno]

Bruno Desthuilliers wrote:

>> Ever seen this from Fuzzyman? It explicitly uses the dict comparison.
>>
>> http://www.voidspace.org.uk/python/articles/OOP.shtml#introduction
> 
> Nope - and the site seems to be down actually. But thanks for the
> pointer anyway.

It works for me, at least now.
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Re: What is Expressiveness in a Computer Language

[Duane Rettig]

Ketil Malde <[EMAIL PROTECTED]> writes:

> "Marshall" <[EMAIL PROTECTED]> writes:
>
>> There are also what I call "packaging" issues, such as
>> being able to run partly-wrong programs on purpose so
>> that one would have the opportunity to do runtime analysis
>> without having to, say, implement parts of some interface
>> that one isn't interested in testing yet. These could also
>> be solved in a statically typed language. (Although
>> historically it hasn't been done that way.)
>
> I keep hearing this, but I guess I fail to understand it.  How
> "partly-wrong" do you require the program to be?

This conclusion is false.  To be "wrong", whether partly or fully,
a program needs to specifically not conform to the requirements that
the programmer gives it.  You are assuming that only a completed
program can be right.  Let me give a counterexample:

Consider this part of a CL program:

CL-USER(1): (defun foo (x)
  (declare (optimize speed (safety 0) (debug 0))
   (fixnum x)
)
  (bar (the fixnum (1+ x
FOO
CL-USER(2): 

This is of course not a complete program, because the function BAR is
not yet defined.  If I try to run it, it will of course get an error.
But does that require then that I call this a "partly wrong" program?
No, of course not; it is not a program; it is a function, and for my
purposes it is completely correct (I've debugged it already :-)

So what can we do with an incomplete program?  Nothing?  Well, no.  Of
course, we can't run it (or can we?).  But even before talking about
running the program, we can at least do some reasoning about it:

 1. It seems to have some static type declarations (in a dynamic
langiuage?  oh my :-).

 2. The 1+ operation limits the kinds of operations that would be
acceptable, even in the absence of static type declarations.

 3. The declarations can be ignored by the CL implementation, so #2
might indeed come into play.  I ensured that the declarations would
be "trusted" in Allegro CL, by declaring high speed and low safety.

 4. I can compile this function.  Note that I get a warning about the
incompleteness of the program:

CL-USER(2): (compile 'foo)
Warning: While compiling these undefined functions were referenced: BAR.
FOO
NIL
NIL
CL-USER(3): 

 5. I can disassemble the function.  Note that it is a complete
function, despite the fact that BAR is undefined:

CL-USER(3): (disassemble 'foo)
;; disassembly of #
;; formals: X
;; constant vector:
0: BAR

;; code start: #x406f07ec:
   0: 83 c0 04 addl eax,$4
   3: 8b 5e 12 movl ebx,[esi+18]  ; BAR
   6: b1 01 movbcl,$1
   8: ff e7 jmp *edi
CL-USER(4): 

 6. I can _even_ run the program!  Yes, I get an error:

CL-USER(4): (foo 10)
Error: attempt to call `BAR' which is an undefined function.
  [condition type: UNDEFINED-FUNCTION]

Restart actions (select using :continue):
 0: Try calling BAR again.
 1: Return a value instead of calling BAR.
 2: Try calling a function other than BAR.
 3: Setf the symbol-function of BAR and call it again.
 4: Return to Top Level (an "abort" restart).
 5: Abort entirely from this (lisp) process.
[1] CL-USER(5): 

 7. But note first that I have many options, including retrying the
call to BAR.  What was this call to BAR?  I can reason about that as
well, by getting a backtrace:

[1] CL-USER(5): :zoom
Evaluation stack:

   (ERROR #)
 ->(BAR 11)
   [... EXCL::%EVAL ]
   (EVAL (FOO 10))
   (TPL:TOP-LEVEL-READ-EVAL-PRINT-LOOP)
   (TPL:START-INTERACTIVE-TOP-LEVEL
  #
  # ...)
[1] CL-USER(6): 

 8. If I then define BAR, with or without compiling it, and then take
that option to retry the call:

[1] CL-USER(6): (defun bar (x) (1- x))
BAR
[1] CL-USER(7): :cont
10
CL-USER(8): 

Hmm, I was able to complete the program dynamically?  Who ever heard
of doing that? :-)

> During development, I frequently sprinkle my (Haskell) program with
> 'undefined' and 'error "implement later"' - which then lets me run the
> implemented parts until execution hits one of the 'undefined's.

Why do it manually?  And what do you do when you've hit the undefined?
Start the program over?

> The "cost" of static typing for running an incomplete program is thus
> simply that I have to name entities I refer to.  I'd argue that this
> is good practice anyway, since it's easy to see what remains to be
> done.

Good practice, yes, but why not have the language help you to practice
it?

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file writing question

[diffuser78]

Hi, I am a newbie so not very confident in file handling.

I want to write to a file atrributes in this fashion
#NameOfComputer:MAC_Address:IP_Address

--computer_details.txt
begins-
IG1:8f00142a123c:192.168.2.101
IG2:8f00142a124d:192.168.2.102
IG3:8f00142a124e:192.168.2.103
IG4:8f00142a124f:192.168.2.104
IG5:8f00142a124a:192.168.2.105
IG6:8f00142a124b:192.168.2.106
--computer_details.txt
ends---

While writing this file I insert "\n" after every line so that details
of every new computer goes into next line for readibility.


After I have to read this file. While reading this file "\n" remains
which I dont want.

Is there a neat way of writing to a file and not having "\n" ?

Please help

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Re: [W2k, wxPython 2.6.1.0] - MDISashDemo bug?

[w.p.]

w.p. wrote:
> When i run MDISashDemo and maximize main frame, minimize and maximize 
> again - LayoutMDIFrame in OnSize dont work more...
> Why?
> 
> I need this feature for main MDI frame with toolbar and statusbar with 
> panels&sizers&bitmapbuttons :)
> 
> Windows 2000, wxPython 2.6.1.0
> 
> w.p.
> 
When i add this code:

 self.Bind(wx.EVT_ACTIVATE, self.OnActivate)

and

 def OnActivate(self, event):
if event.GetActive():
 wx.LayoutAlgorithm().LayoutMDIFrame(self)

all is ok.

Small improvement in demo :)

w.p.
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Re: Having problems with strings in HTML

[Sion Arrowsmith]

Richard Brodie <[EMAIL PROTECTED]> wrote:
>"Sion Arrowsmith" <[EMAIL PROTECTED]> wrote in message 
>news:[EMAIL PROTECTED]
> [ ... ]
>>>By the way, you _do_ realize that your "&" characters should be escaped
>>>as "&", don't you?
>> No they shouldn't. They part of the url, which is (IIRC) a CDATA
>> attribute of the A element, not PCDATA.
>It is CDATA but ampersands still need to be escaped. 

I'll take back that "shouldn't" as per Fredrik's post. Maybe they
*should* be escaped, but they don't *need* to be. I've never, and
never seen, anyone doing that in a decade of writing cgi; a straw poll
of peers suggests that the majority would write the former; and I've
never encountred a browser getting tripped up by it. I suppose you
might need it if you've got parameters called quot or nbsp, but it's
hardly the most broken way of writing HTML.

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Re: languages with full unicode support

[Tin Gherdanarra]

Oliver Bandel wrote:
> 
> こんいちわ Xah-Lee san ;-)

Uhm, I'd guess that Xah is Chinese. Be careful
with such things in real life; Koreans might
beat you up for this. Stay alive!


> 
> 
> Xah Lee wrote:
> 
>> Languages with Full Unicode Support
>>
>> As far as i know, Java and JavaScript are languages with full, complete
>> unicode support. That is, they allow names to be defined using unicode.
> 
> 
> Can you explain what you mena with the names here?
> 
> 
>> (the JavaScript engine used by FireFox support this)
>>
>> As far as i know, here's few other lang's status:
>>
>> C → No.
> 
> 
> Well, is this (only) a language issue?
> 
> On Plan-9 all things seem to be UTF-8 based,
> and when you use C for programming, I would think
> that C can handle this also.
> 
> But I only have read some papers about Plan-9 and did not developed on 
> it
> 
> Only a try to have a different view on it.
> 
> If someone knows more, please let us know :)
> 
> 
> Ciao,
>Oliver


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Re: Inconsistent float behaviour on "inf" - current state?

[Scott David Daniels]

Peter Knörrich wrote:

>  why "float('inf')" isn't supported everywhere, and I
> understand the underlying problem:
> libc simply isn't that good - never mind standard - with regard to floats.
I think you believe there is an underlying model of floating point
numbers that all machines share.  That is not true.  Many systems
(even those that support IEEE 754) make distinct choices about what
particular bit patterns in memory represent what particular values.

You can take a pickle of a data structure in CPython on one machine,
carry it to a different machine with a different CPU & FPU and a
different OS, and reasonably expect that the unpickled data structure
running on the CPython on the other machine will produce essentially the
same value.  That is _amazing_.  You might not have the same number
of bits of precision, you might not have the same range of exponents,
and the base of the exponent might even be different (well, ... perhaps
nobody is running Python on 360s -- I may exaggerate here).  This is not
accomplished by lots of clever coding of distinct implementations across
the range of machines CPython runs on.  It is accomplished by staying
close to the middle of the road in the C89 standard.  And it breaks down
for infinities and the various denormals and NaNs that you can at least
detect in C99.

C89, the standard we go by for CPython, provides pretty good support
for floating point numbers in "reasonable" ranges with "reasonable"
amounts of precision.  That is to say, you can calculate with C doubles
and get pretty similar results for the same C program running on quite
different compilers, operating systems, and hardware _if_ you "walk the
middle of the road" (staying away from rough edges, boundary values,
things like calculating sin(1e300) [trigs work better w/in -2pi to 2pi]
and the like.  C89 does not mention the Not-A-Number group at all, and
only says that infinity is something that an "implementation may
support."  That "may" means that a C89 compiler is free to do nothing
for Infinities, and even if it does something, it it doesn't have to
behave like some other C89 compiler's version of what to do with
Infinities.  So it is no wonder that values like plus and minus
infinity "behave funny" across different CPython systems.

In the eighties (when C89 was being worked on), it was not clear whether
IEEE 754 would be _the_ standard or _a_ standard for floating point.  It
would have been pointless to force all C implementers (and they included
Lifeboat Systems who did C compilers for Z80s as well as Cray Research,
who did C compilers for slightly larger machines) to specify how to make
positive and negative zeroes, how and when to produce "denormalized"
numbers, how to produce positive and negative infinity (and whether they
are distinct from each other),  how create the various signaling and
quiet NaNs when may systems did not have IEEE 754 floating point
hardware.

C is kind of a "glorified assembler," and (as such) it reveals the
hardware it works on.  That is why the C expression ((-7) % 4) can be
1 or -1; different hardware solves that problem differently, and C
doesn't want to slow down all divisions on some hardware just to get
a consistent result.  If you stick to positive numbers for division,
both kinds of hardware get the same result, and the programmer can
put the test in if he needs it.  It would not be in the spirit of C
to dictate a floating point behavior that would require a lot of
code generated on each operation, and without common hardware, the
infinity / denormal / NaN behavior would mean code at every floating
point operation.  The C standards body was not interested in that work.

--Scott David Daniels
[EMAIL PROTECTED]
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Re: What is Expressiveness in a Computer Language

[Greg Buchholz]

Chris F Clark wrote:
> Very impressive.  It looks right to me and simple enough to
> understand.  I must find the time to learn a modern FP language.  Can
> you write a fold for this that prints the data as a binary tree of
> triples?  I have to believe it isn't that hard

{- Refactoring this as a fold is left as an exercise to the reader -}

data Clark a b c = Nil | Cons a (Clark b c (a,a)) deriving Show

clark =
  (Cons 42 (Cons 3.14 (Cons "abc"
  (Cons (1,2) (Cons (1.2,3.4) (Cons ("foo","bar")
  (Cons ((9,8),(7,6)) (Cons ((0.1,0.2),(0.3,0.4))
(Cons (("w","x"),("y","z")) Nil)

main = print (toTree clark)

data Tree a = Empty | Node a (Tree a) (Tree a) deriving Show

toTree :: Clark a b c -> Tree (a,b,c)
toTree (Cons x (Cons y (Cons z rest)))
 = Node (x,y,z)
(toTree (fst (lift_c rest)))
(toTree (snd (lift_c rest)))
toTree _ = Empty

lift_c :: Clark (a,a) (b,b) (c,c) -> (Clark a b c, Clark a b c)
lift_c Nil = (Nil,Nil)
lift_c (Cons (x,y) rest) = (Cons x (fst (lift_c rest)),
Cons y (snd (lift_c rest)))

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Re: What is Expressiveness in a Computer Language

[Joe Marshall]

Marshall wrote:
>
> Yes, an important question (IMHO the *more* important question
> than the terminology) is what *programs* do we give up if we
> wish to use static typing? I have never been able to pin this
> one down at all.

It would depend on the type system, naturally.

It isn't clear to me which programs we would have to give up, either.
I don't have much experience in sophisticated typed languages.  It is
rather easy to find programs that baffle an unsophisticated typed
language (C, C++, Java, etc.).

Looking back in comp.lang.lisp, I see these examples:

(defun noisy-apply (f arglist)
  (format t "I am now about to apply ~s to ~s" f arglist)
  (apply f arglist))

(defun blackhole (argument)
  (declare (ignore argument))
  #'blackhole)

But wait a sec.  It seems that these were examples I invented in
response to the same question from you!


>
> The real question is, are there some programs that we
> can't write *at all* in a statically typed language, because
> they'll *never* be typable?

Certainly!  As soon as you can reflect on the type system you can
construct programs that type-check iff they fail to type-check.

> > Perhaps, there is no such beast.  Or, perhaps I just can't formulate
> > it.  Or, perhaps we have static type checkers which can do
> > computations of unbounded complexity.  However, I thought that one of
> > the characteristics of type systems was that they did not allow
> > unbounded complexity and weren't Turing Complete.
>
> The C++ type system is Turing complete, although in practical terms
> it limits how much processing power it will spend on types at
> compile time.

I think templates only have to expand to seven levels, so you are
severely limited here.

> > If you allow Turing Complete type systems, then I would say no--every
> > bug can be reforumlated as a type error.  If you require your type
> > system to be less powerful, then some bugs must escape it.
>
> I don't think so. Even with a Turing complete type system, a program's
> runtime behavior is still something different from its static behavior.
> (This is the other side of the "types are not tags" issue--not only
> is it the case that there are things static types can do that tags
> can't, it is also the case that there are things tags can do that
> static types can't.)

I agree.  The point of static checking is to *not* run the program.  If
the type system gets too complicated, it may be a de-facto interpreter.

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Re: file writing question

[Bruno Desthuilliers]

[EMAIL PROTECTED] wrote:
> Hi, I am a newbie so not very confident in file handling.
> 
> I want to write to a file atrributes in this fashion
> #NameOfComputer:MAC_Address:IP_Address
> 
> --computer_details.txt
> begins-
> IG1:8f00142a123c:192.168.2.101
> IG2:8f00142a124d:192.168.2.102
> IG3:8f00142a124e:192.168.2.103
> IG4:8f00142a124f:192.168.2.104
> IG5:8f00142a124a:192.168.2.105
> IG6:8f00142a124b:192.168.2.106
> --computer_details.txt
> ends---
> 
> While writing this file I insert "\n" after every line so that details
> of every new computer goes into next line for readibility.
> 
> 
> After I have to read this file. While reading this file "\n" remains
> which I dont want.

Then strip it:

for line in open('computer_details.txt'):
   name, mac, ip = line.strip().split(':')
   # ...

> Is there a neat way of writing to a file and not having "\n" ?

Yes : don't add the newline after every line. But note that this may
make the file a bit more difficult to read and parse for both your
program and you !-)

Also, may I suggest that you read the doc for the CSV module ?


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p in '[EMAIL PROTECTED]'.split('@')])"
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Re: new python icons for windows

[chowychow]

Istvan Albert wrote:
> [EMAIL PROTECTED] wrote:
>
> > > For example it resembles the icon for text files.
> >
> > This is intentional: to make it obvious that .py files are the
> > readable, editable scripts, contrasting with .pyc's binary gunk -
>
> I think this is a mistake, it does not seem obious, all it does is just
>  blends in and does not separate the python files from regular text
> files.
>
> Also the black icons for pyc files are far more visible and
> stand out much more than the white ones. If anything I wish the pyc had
> no icons at all or was invisible, I mean how often do you need to do
> any work with pyc files...

I agree with those points after trying out the icons.  Something about
the icons seems blurry (perhaps it's the yellow snake with the poorly
visible white eye.  Or it could be the paper that doesn't seem to have
enough contrast on the top (I have white background behind them.)  To
my eyes, the pyc stick out also.  I almost want to swap the two since
the pyc files look so striking.

I do like the egg icons very much.

Good work!
-Kevin Deenanauth

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Re: Unbound Local error? How?

[Steve Holden]

Hari Sekhon wrote:
> Bruno Desthuilliers wrote:
> 
>>Hari Sekhon wrote:
>>  
>>
>>>I've got some code as follows:
>>>
>>>import re
>>>re_regexname = re.compile('abc')
>>>
>>>.
>>>. various function defs
>>>.
>>>
>>>def func1():
>>>   ...
>>>   func2()
>>>   ...
>>>
>>>def func2():
>>>   if re_regexname.match('abc'):
>>>  
>>>
>>>if __name__ == '__main__':
>>>   func1()
>>>
>>>
>>>but this returns the Traceback:
>>>
>>>UnboundLocalError: local variable 're_regexname' referenced before
>>>assignment
>>>
>>>
>>
>>this is *not* the traceback. This is only the error message. The
>>traceback contains all needed informations (or at least all possible
>>information at this point) to know what happened. But you did not post
>>the traceback. Nor did you post the minimal runnable code snippet
>>producing this error.
>>
>>  
>>
>>>How?
>>>
>>>
>>
>>How could we know ?
>>
>>
>>  
>>
> 
> sorry, I know it looks like I was being stingy but the traceback was not 
> that helpful, not without seeing more a huge amount more of the code. I 
> was trying to abbreviate.
> 
> Traceback (most recent call last):
>   File "./backup.py", line 649, in ?
> backup(machine,share)
>   File "./backup.py", line 364, in backup
> backupdir(source,destination)
>   File "./backup.py", line 398, in backupdir
> (dirlist,filelist) = getdirlisting( source )
>   File "./backup.py", line 445, in getdirlisting
> if re_skip_dirs.match(x):
> UnboundLocalError: local variable 're_skip_dirs' referenced before 
> assignment
> 
> This doesn't really show that much, I figured the problem was the following:
> 
> def getdirlisting():
>  re_skip_dirs = re_skip_top_dirs   #Here's the culprit
> 
> where both these regex compiled objects were declared at the top level, 
> it seems that the assignment is trying to use the local variable 
> re_skip_top_dirs which doesn't exist, that's why I'm getting a 
> traceback, commenting out this line it runs fine.
> 
> -h
> 
> 
The error is simply that you are making an assignment *somewhere* inside 
your function body, so the compiler is treating the variable as local, 
masking the module-level global name. Consequently when you try to read 
its value you are told that the local variable has not yet been bound to 
a value.

A "global" statement inside the function body will fix the problem. You 
could also add a keyword argument (never used except to set a default 
for it in the "def" statement).

regards
  Steve
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Re: [W2k, wxPython 2.6.1.0] - MDISashDemo bug?

[Steve Holden]

w.p. wrote:
> w.p. wrote:
> 
>>When i run MDISashDemo and maximize main frame, minimize and maximize 
>>again - LayoutMDIFrame in OnSize dont work more...
>>Why?
>>
>>I need this feature for main MDI frame with toolbar and statusbar with 
>>panels&sizers&bitmapbuttons :)
>>
>>Windows 2000, wxPython 2.6.1.0
>>
>>w.p.
>>
> 
> When i add this code:
> 
>  self.Bind(wx.EVT_ACTIVATE, self.OnActivate)
> 
> and
> 
>  def OnActivate(self, event):
> if event.GetActive():
>  wx.LayoutAlgorithm().LayoutMDIFrame(self)
> 
> all is ok.
> 
> Small improvement in demo :)
> 
Well done! Do you know how to feed this information on to the developers 
(probably Robin Dunn)? All such changes are valuable.

regards
  Steve
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Re: What is Expressiveness in a Computer Language

[Diez B. Roggisch]

>> The C++ type system is Turing complete, although in practical terms
>> it limits how much processing power it will spend on types at
>> compile time.
> 
> I think templates only have to expand to seven levels, so you are
> severely limited here.

You can adjust the iteration-depth. However, as turing-complete implies the
potential to create infinite loops - it enforces _some_ boundary. Otherwise
the user hitting C-c will do :)
 
Diez
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Re: Python database access

[Damjan]

> The odbc module is part of the Python Standard Library. 

Since when?


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Exchanging data with a C program using shared memory (sysV IPC)

[Al]

Hello,

I want my python application to communicate with an legacy C program which
read/write data in a shared memory (Unix Sys V IPC).

It seems that there are no official shm nor sysV ipc module, and that
non-official ones are dead. I can't modify the C code to change its
communication method.

How would you solve this problem using python ?
Is there any reason there is no official shm for python ?


I could write a C code which communicates with my python application
using mmap or something else and with the old C code using shmat(), but
this is a rather ugly solution.

Thanks in advance.

---
Al

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Re: file writing question

[diffuser78]

Thanks BrunoThis helps me.

Bruno Desthuilliers wrote:
> [EMAIL PROTECTED] wrote:
> > Hi, I am a newbie so not very confident in file handling.
> >
> > I want to write to a file atrributes in this fashion
> > #NameOfComputer:MAC_Address:IP_Address
> >
> > --computer_details.txt
> > begins-
> > IG1:8f00142a123c:192.168.2.101
> > IG2:8f00142a124d:192.168.2.102
> > IG3:8f00142a124e:192.168.2.103
> > IG4:8f00142a124f:192.168.2.104
> > IG5:8f00142a124a:192.168.2.105
> > IG6:8f00142a124b:192.168.2.106
> > --computer_details.txt
> > ends---
> >
> > While writing this file I insert "\n" after every line so that details
> > of every new computer goes into next line for readibility.
> >
> >
> > After I have to read this file. While reading this file "\n" remains
> > which I dont want.
>
> Then strip it:
>
> for line in open('computer_details.txt'):
>name, mac, ip = line.strip().split(':')
># ...
>
> > Is there a neat way of writing to a file and not having "\n" ?
>
> Yes : don't add the newline after every line. But note that this may
> make the file a bit more difficult to read and parse for both your
> program and you !-)
>
> Also, may I suggest that you read the doc for the CSV module ?
>
>
> --
> bruno desthuilliers
> python -c "print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
> p in '[EMAIL PROTECTED]'.split('@')])"

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Re: [W2k, wxPython 2.6.1.0] - MDISashDemo bug?

[w.p.]

Steve Holden wrote:

>>
> Well done! Do you know how to feed this information on to the developers 
> (probably Robin Dunn)? All such changes are valuable.
> 

Hmm... i dont know. wxpython.org -> "submit a patch" or "Report a bug" ?

w.p.
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Re: What is Expressiveness in a Computer Language

[QCD Apprentice]

Joe Marshall wrote:
> Marshall wrote:
>> Yes, an important question (IMHO the *more* important question
>> than the terminology) is what *programs* do we give up if we
>> wish to use static typing? I have never been able to pin this
>> one down at all.
> 
> It would depend on the type system, naturally.
> 
> It isn't clear to me which programs we would have to give up, either.
> I don't have much experience in sophisticated typed languages.  It is
> rather easy to find programs that baffle an unsophisticated typed
> language (C, C++, Java, etc.).
> 
> Looking back in comp.lang.lisp, I see these examples:
> 
> (defun noisy-apply (f arglist)
>   (format t "I am now about to apply ~s to ~s" f arglist)
>   (apply f arglist))
> 
> (defun blackhole (argument)
>   (declare (ignore argument))
>   #'blackhole)
> 
> But wait a sec.  It seems that these were examples I invented in
> response to the same question from you!
> 
> 
>> The real question is, are there some programs that we
>> can't write *at all* in a statically typed language, because
>> they'll *never* be typable?
> 
> Certainly!  As soon as you can reflect on the type system you can
> construct programs that type-check iff they fail to type-check.

Sorry, but can you elaborate on this last point a little?  I think I 
missed something.
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Re: What is Expressiveness in a Computer Language

[David Hopwood]

Marshall wrote:
> David Hopwood wrote:
>>Marshall wrote:
>>
>>>The real question is, are there some programs that we
>>>can't write *at all* in a statically typed language, because
>>>they'll *never* be typable?
>>
>>In a statically typed language that has a "dynamic" type, all
>>dynamically typed programs are straightforwardly expressible.
> 
> So, how does this "dynamic" type work?



> It can't simply be the "any" type, because that type has no/few
> functions defined on it.

It isn't. From the abstract of the above paper:

  [...] even in statically typed languages, there is often the need to
  deal with data whose type cannot be determined at compile time. To handle
  such situations safely, we propose to add a type Dynamic whose values are
  pairs of a value v and a type tag T where v has the type denoted by T.
  Instances of Dynamic are built with an explicit tagging construct and
  inspected with a type safe typecase construct.

"Gradual typing" as described in
 is
another alternative. The difference between gradual typing and a
"dynamic" type is one of convenience rather than expressiveness --
gradual typing does not require explicit tagging and typecase constructs.

-- 
David Hopwood <[EMAIL PROTECTED]>
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Re: How to disable tk inclusion in py build

[Fredrik Lundh]

[EMAIL PROTECTED] wrote:

> I'd like to disable the inclusion of tk graphics lib in my py build.
> Looked around but couldn't find a clear answer. Which one of
> the following would I need to use in the configure step:
>   --disable-tkbuild
>   --without-tk

since _tkinter.so is only built if it's found by the setup script,
and if built, it's only loaded if you actually use it, why bother 
"disabling" it ?



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Re: Extracting 3-byte integers

[Bob Greschke]

>I have some binary data read from a file that is arranged like
>
>   <3-byte int> <3-byte int> <3-byte int> etc.
>
> The "ints" are big-endian and there are 169 of them.  Is there any clever 
> way to convert these to regular Python ints other than (struct) unpack'ing 
> them one at a time and doing the math?

Thanks guys!  I was looking for a 'one liner' of some kind, but I guess 
there isn't one (too bad you can't tell array or struct.unpack how many 
bytes you want an integer to be).  Yeah, these are signed ints so I'll have 
to convert them.

To me balancing my checkbook involves higher "math". :)

Bob


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Re: What is Expressiveness in a Computer Language

[Chris Smith]

George Neuner  wrote:
> We're talking at cross purposes.  I'm questioning whether a strong
> type system can be completely static as some people here seem to
> think. I maintain that it is simply not possible to make compile time
> guarantees about *all* runtime behavior and that, in particular,
> narrowing conversions will _always_ require runtime checking.

Nah, we're not at cross-purposes.  I'm discussing the same thing you 
are.  My answer is that while narrowing conversion are not (by 
definition) type-safe, a sufficiently strong type system can remove 
these type-unsafe narrowing conversions from a program.

> Again, the discussion is about narrowing the result.  It doesn't
> matter how much the compiler knows about the ranges.  When the
> computation mixes types, the range of the result can only widen as the
> compiler determines the types involved.

Well, there are certain operations that can reduce the range.  For 
example, dividing a number that's known to be in the range 6-10 by the 
exact constant 2 yields a result that's guaranteed to be in the range 3-
5.  That's a smaller range.

That said, though, there is a more fundamental point here.  When you 
perform a a narrowing type conversion, one of two things must be true: 
(a) you know more about the types than the compiler, and thus know that 
the conversion is safe, or (b) your code is broken.  Exluding the 
possibility that you've written buggy code, you must possess some 
knowledge that convinces you the conversion is safe.  In that case, we 
need only allow the type system to have that same knowledge, and the 
problem is solved.

(One thing worth pointing out here is that it's quite possible that you 
want to do something different depending on the kind of data.  In that 
case, the sufficiently powerful type system would need to have rules so 
that an if statemement creates a modified type environment to take that 
into account.  This is different from a runtime type check, in that you 
are writing explicit code that provides correct program behavior in 
either case.)

-- 
Chris Smith - Lead Software Developer / Technical Trainer
MindIQ Corporation
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Re: What is Expressiveness in a Computer Language

[Chris Smith]

Dr.Ruud <[EMAIL PROTECTED]> wrote:
> > So it seems to me that we have this ideal point at which it is
> > possible to write all correct or interesting programs, and impossible
> > to write buggy programs.
> 
> I think that is a misconception. Even at the idealest point it will be
> possible (and easy) to write buggy programs. Gödel!

I agree.  I never said that the ideal point is achievable... only that 
there is a convergence toward it.  (In some cases, that convergence may 
have stalled at some equilibrium point because of the costs of being 
near that point.)

-- 
Chris Smith - Lead Software Developer / Technical Trainer
MindIQ Corporation
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Re: What is Expressiveness in a Computer Language

[Marshall]

David Hopwood wrote:
> Marshall wrote:
> > David Hopwood wrote:
> >>Marshall wrote:
> >>
> >>>The real question is, are there some programs that we
> >>>can't write *at all* in a statically typed language, because
> >>>they'll *never* be typable?
> >>
> >>In a statically typed language that has a "dynamic" type, all
> >>dynamically typed programs are straightforwardly expressible.
> >
> > So, how does this "dynamic" type work?
>
> 
>
> > It can't simply be the "any" type, because that type has no/few
> > functions defined on it.
>
> It isn't. From the abstract of the above paper:
>
>   [...] even in statically typed languages, there is often the need to
>   deal with data whose type cannot be determined at compile time. To handle
>   such situations safely, we propose to add a type Dynamic whose values are
>   pairs of a value v and a type tag T where v has the type denoted by T.
>   Instances of Dynamic are built with an explicit tagging construct and
>   inspected with a type safe typecase construct.

Well, all this says is that the type "dynamic" is a way to explicitly
indicate the inclusion of rtti. But that doesn't address my objection;
if a typesafe typecase construct is required, it's not like using
a dynamic language. They don't require typecase to inspect values
before one can, say, invoke a function.


> "Gradual typing" as described in
>  is
> another alternative. The difference between gradual typing and a
> "dynamic" type is one of convenience rather than expressiveness --
> gradual typing does not require explicit tagging and typecase constructs.

Perhaps this is the one I should read; it sounds closer to what I'm
talking about.


Marshall

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Questions about OSS projects.

[bio_enthusiast]

I was wondering how to go about starting an open source project for
doing routine biological problems? There is a plethora of scripts and
a fairly large biopython project to back up anyone who tried, these
however cater to the bioinformatics community and it loses the vast
majority of the wet-lab scientists. How can someone who is used to
writing small scripts and doing wet-lab work contribute to the open
source community? Starting software projects seems to be the domain of
people with much more experience and skill but there are some serious
needs by people who do not have the skills to upkeep any software
based project.

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Re: using pydoc in an application

[timw.google]

I went and looked at the pydoc.py code, and it looks like it isn't
really meant to be used from inside another python program. After some
tinkering arond with my code, I ended up with this: (Google is messing
up my indentation)

(in my __init__ function)
...

menuBar.addmenuitem('Help', 'command', '',
   command=self.run_pydoc,
   label='Run pydoc (module
help GUI)')

...

def run_pydoc(self):
"""Run pydoc -g for gui based help"""
if 'linux' in sys.platform:
os.system('pydoc -g')
if 'win32' in sys.platform:
os.system(os.path.join(sys.prefix,
   'Tools', 'Scripts',
   'pydocgui.pyw'))
return

A bit of a kludge, but it works for me.

timw.google wrote:
> Hi all,
>
> I'm discovering pydoc, and it seems to me that this is a great way to
> have online documentation for my application. Are there any examples of
> using this in some kind of help menu in an application?  I've tried to
> just bind pydoc.gui() to a menu item, but this just brings up the GUI
> for pydoc, and the user still needs to search for the module before the
> browser comes up, and when I quit serving pydoc.gui(), my application
> dies along with it. Also, I need to get out of python to use pydoc.gui
> again, or I get
>
> error: (98, 'Address already in use')
>
> I'm sure there's a better way to take advantage of this module and my
> docstrings to get some online help.  I'm using Tkinter and Pmw, but
> maybe it's time to convert all this to wxWidgets?
> 
> Thanks for any help.

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Re: What is Expressiveness in a Computer Language

[Marshall]

Joe Marshall wrote:
> Marshall wrote:
> >
> > Yes, an important question (IMHO the *more* important question
> > than the terminology) is what *programs* do we give up if we
> > wish to use static typing? I have never been able to pin this
> > one down at all.
>
> It would depend on the type system, naturally.

Naturally!


> It isn't clear to me which programs we would have to give up, either.
> I don't have much experience in sophisticated typed languages.  It is
> rather easy to find programs that baffle an unsophisticated typed
> language (C, C++, Java, etc.).

C and Java, certainly, but I'm wary these days about making
any statement about limitations on C++'s type system, for it is
subtle and quick to anger.


> Looking back in comp.lang.lisp, I see these examples:
>
> (defun noisy-apply (f arglist)
>   (format t "I am now about to apply ~s to ~s" f arglist)
>   (apply f arglist))
>
> (defun blackhole (argument)
>   (declare (ignore argument))
>   #'blackhole)
>
> But wait a sec.  It seems that these were examples I invented in
> response to the same question from you!

Ah, how well I remember that thread, and how little I got from it.

My memories of that thread are
1) the troll who claimed that Java was unable to read two numbers from
standard input and add them together.
2) The fact that all the smart people agreed the blackhole
function indicated something profound.
3) The fact that I didn't understand the black hole function.

The noisy-apply function I think I understand; it's generic on the
entire arglist. In fact, if I read it correctly, it's even generic
on the *arity* of the function, which is actually pretty impressive.
True? This is an issue I've been wrestling with in my own type
system investigations: how to address genericity across arity.

Does noisy-apply get invoked the same way as other functions?
That would be cool.

As to the black hole function, could you explain it a bit? I apologize
for my lisp-ignorance. I am sure there is a world of significance
in the # ' on the third line, but I have no idea what it is.


> > > If you allow Turing Complete type systems, then I would say no--every
> > > bug can be reforumlated as a type error.  If you require your type
> > > system to be less powerful, then some bugs must escape it.
> >
> > I don't think so. Even with a Turing complete type system, a program's
> > runtime behavior is still something different from its static behavior.
> > (This is the other side of the "types are not tags" issue--not only
> > is it the case that there are things static types can do that tags
> > can't, it is also the case that there are things tags can do that
> > static types can't.)
>
> I agree.  The point of static checking is to *not* run the program.  If
> the type system gets too complicated, it may be a de-facto interpreter.

Aha! A lightbulb just want off.

Consider that a program is a function parameterized on its input.
Static
analysis is exactly the field of what we can say about a program
without
know the values of its parameters.


Marshall

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Re: Questions about OSS projects.

[Grant Edwards]

On 2006-06-27, bio_enthusiast <[EMAIL PROTECTED]> wrote:

> I was wondering how to go about starting an open source
> project for doing routine biological problems?

Generally you either start writing code to fulfill a need of
yours, or you pay somebody else to write it for you.

> There is a plethora of scripts and a fairly large biopython
> project to back up anyone who tried, these however cater to
> the bioinformatics community and it loses the vast majority of
> the wet-lab scientists. How can someone who is used to writing
> small scripts and doing wet-lab work contribute to the open
> source community?

For existing projects, you can help a lot by submitting good
bug reports, documentation enhancements or translations,
patches, etc.

> Starting software projects seems to be the domain of people
> with much more experience and skill but there are some serious
> needs by people who do not have the skills to upkeep any
> software based project.

That's what money is for.  People with no need for (or interest
in) program X (and indeed don't even know about the need)
aren't going to write program X unless you pay them to.  You
could try to recruit some SW types to write the code for free,
but they're probably already busy working on OSS projects that
they need/want. 

There are sites where you can offer "bounties" as incentives
for people to work on the OSS you want them to work on.

-- 
Grant Edwards   grante Yow!  Are you still
  at   SEXUALLY ACTIVE? Did you
   visi.comBRING th' REINFORCEMENTS?
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Problem with sets and Unicode strings

[Dennis Benzinger]

Hi!

The following program in an UTF-8 encoded file:


# -*- coding: UTF-8 -*-

FIELDS = ("Fächer", )
FROZEN_FIELDS = frozenset(FIELDS)
FIELDS_SET = set(FIELDS)

print u"Fächer" in FROZEN_FIELDS
print u"Fächer" in FIELDS_SET
print u"Fächer" in FIELDS


gives this output


False
False
Traceback (most recent call last):
   File "test.py", line 9, in ?
 print u"FÀcher" in FIELDS
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 1: 
ordinal not in range(128)


Why do the first two print statements succeed and the third one fails 
with an exception?

Why does the use of set/frozenset remove the exception?


Thanks,
Dennis
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Re: What is Expressiveness in a Computer Language

[David Hopwood]

Marshall wrote:
> David Hopwood wrote:
>>Marshall wrote:
>>>David Hopwood wrote:
Marshall wrote:

>The real question is, are there some programs that we
>can't write *at all* in a statically typed language, because
>they'll *never* be typable?

In a statically typed language that has a "dynamic" type, all
dynamically typed programs are straightforwardly expressible.
>>>
>>>So, how does this "dynamic" type work?
>>
>>
>>
>>>It can't simply be the "any" type, because that type has no/few
>>>functions defined on it.
>>
>>It isn't. From the abstract of the above paper:
>>
>>  [...] even in statically typed languages, there is often the need to
>>  deal with data whose type cannot be determined at compile time. To handle
>>  such situations safely, we propose to add a type Dynamic whose values are
>>  pairs of a value v and a type tag T where v has the type denoted by T.
>>  Instances of Dynamic are built with an explicit tagging construct and
>>  inspected with a type safe typecase construct.
> 
> Well, all this says is that the type "dynamic" is a way to explicitly
> indicate the inclusion of rtti. But that doesn't address my objection;
> if a typesafe typecase construct is required, it's not like using
> a dynamic language. They don't require typecase to inspect values
> before one can, say, invoke a function.

I was answering the question posed above: "are there some programs that
we can't write *at all* in a statically typed language...?"

>>"Gradual typing" as described in
>> is
>>another alternative. The difference between gradual typing and a
>>"dynamic" type is one of convenience rather than expressiveness --
>>gradual typing does not require explicit tagging and typecase constructs.
> 
> Perhaps this is the one I should read; it sounds closer to what I'm
> talking about.

Right; convenience is obviously important, as well as expressiveness.

-- 
David Hopwood <[EMAIL PROTECTED]>
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