Re: sqlite utf8 encoding error

[Manlio Perillo]

On 18 Nov 2005 09:09:24 -0800, "Greg Miller" <[EMAIL PROTECTED]>
wrote:

>Thank you for all your suggestions.  I ended up casting the string to
>unicode prior to inserting into the database.  
>

Don't do it by hand if it can be done by an automated system.

Try with:

from pysqlite2 import dbapi2 as sqlite

def adapt_str(s):
# if you have declared this encoding at begin of the module
return s.decode("iso-8859-1") 

sqlite.register_adapter(str, adapt_str)


Read pysqlite documentation for more informations:
http://initd.org/pub/software/pysqlite/doc/usage-guide.html



Regards  Manlio Perillo
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termios.tcgetattr(fd) error: (22, 'Invalid argument')

[Petr Jakes]

On my box (Fedora Core4, Python 2.4.1) I am getting following error:
>>> import termios, sys
>>> fd = sys.stdin.fileno()
>>> oldSettings = termios.tcgetattr(fd)
Traceback (innermost last):
  File "", line 1, in ?
error: (22, 'Invalid argument')

Thanks for your comments.
Petr Jakes

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Re: Reinvent no more forever

[Ben Finney]

[EMAIL PROTECTED] wrote:
> Ben Finney wrote:
> > How do we deal with the rampant proliferation of a zillion
> > implementations of some standard idiom in PyPI?
> 
> How about some kind of "mega util" package? One big package with all
> those recurring reinventions. If it gets popular enough, I'm sure it
> could stop so much reinvention.

No, you'd just ensure there would be several, competing, incompatible
"mega util" packages. Plus, you'd have the additional problem of
depending on a big, low-coherence package for one or two idioms within
it.

> I'm thinking that a Wiki would be quite suitable for development, to
> incite more contributions (rather than only CVS).

http://wiki.python.org/moin/>

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Ben Finney
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Re: Underscores in Python numbers

[Stefan Rank]

on 19.11.2005 06:56 Steven D'Aprano said the following:
[snip]
> 
> Perhaps Python should concatenate numeric literals at compile time:
> 
> 123 456 is the same as 123456.
> 
> Off the top of my head, I don't think this should break any older code,
> because 123 456 is not currently legal in Python.

+1

but only allow (a single ?) space(s), otherwise readability issues ensue.

The other idea of teaching int() about separator characters has 
internationalis/zation issues:
In many European countries, one would naturally try::

   int('500.000,23')

instead of::

   int('500,000.23')

--
stefan

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Re: Underscores in Python numbers

[bearophileHUGS]

Steven D'Aprano:
> Perhaps Python should concatenate numeric literals at compile time:
> 123 456 is the same as 123456.

I think using the underscore it is more explicit:
n = 123_456

Alternatively the underscore syntax may be used to separate the number
from its base:
22875 == 22875_10 == 595b_16 == 123456_7
But probably this is less commonly useful (and not much explicit).

Bye,
bearophile

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Re: the PHP ternary operator equivalent on Python

[[EMAIL PROTECTED]]

Steven D'Aprano wrote:
> L = ["zero" if n == 0 else \
> "negative " + ("odd" if n % 2 else "even") if n < 0 else \
> "odd" if n % 2 else "even" for n in range(8)]
>
BTW, the continuation is not necessary I believe.

[ x==0 and "zero" or ["","-"][x < 0] + ("even", "odd")[x%2] for x in
range(8) ]

isn't too bad. though I like the C one a bit more(as it doesn't
overload the and/or)

[ x==0 ? "zero" : ["","-"][x < 0] + ("even", "odd")[x%2] for x in
range(8) ]

As it is still a very straight forward flow(from left to right, without
"internal decision split in between").

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Re: about try and exception

[Bruno Desthuilliers]

Shi Mu a écrit :
> On 11/17/05, Carl J. Van Arsdall <[EMAIL PROTECTED]> wrote:
> 
(Carl's top-post corrrected. Carl, please do not top-post)
>>
>>
>>Ben Bush wrote:
>>
>>>I wrote the following code to test the use of "try...exception",
>>>and I want n to be printed out. However, the following code's output is:
>>>Traceback (most recent call last):
>>>  File
>>>"C:\Python23\lib\site-packages\Pythonwin\pywin\framework\scriptutils.py",
>>>line 310, in RunScript
>>>exec codeObject in __main__.__dict__
>>>  File "C:\py\use\tryExVa.py", line 7, in ?
>>>print n
>>>NameError: name 'n' is not defined
>>>
>>>the code is here:
>>>
>>>try:
>>>m=2/0
>>>n=1/2
>>>except ZeroDivisionError:
>>>pass
>>>print "Yes!!! This line will always print"
>>>print n

 >>I would think that when the exception occurs the interpreter exits the
 >>block of code it is currently in and enters the exception block.
 >>
 >>Thus the line n = 1/2 would never get executed.
>
> It is true. 

Indeed...

> If I want to run the statement after the division error
> such as n=1/2, what should I do?

Depends on what you mean by "after". But I think this is what you want:

try:
   m = 2 / 0
except ZeroDivisionError:
   m = 0 # or whatever default value
n = 1/2


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Re: Underscores in Python numbers

[[EMAIL PROTECTED]]

Stefan Rank wrote:
> The other idea of teaching int() about separator characters has
> internationalis/zation issues:
> In many European countries, one would naturally try::
>
>int('500.000,23')
>
> instead of::
>
>int('500,000.23')

That is why I said

"Of course, also support the locale variant where the meaning of ","
and
"." is swapped in most European countries. "

We are seeing the same about base 2, 8, 10, 16.

May be :

int("E500.000,23")

as we are using :

0x 

already for hex number

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Re: examining python objects

[Bruno Desthuilliers]

[EMAIL PROTECTED] a écrit :
> Is there a function/class/module/whatever I can use to
> look at objects?  I want something that will print the object's
> value (if any) in pretty-printed form, and list all it's attributes
> and their values.  And do all that recursively.
> I want to be able to find out everything about an object that
> Python can introspectively find out.

Then check the inspect module

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Re: How to write an API for a Python application?

[Piet van Oostrum]

> Duncan Grisby <[EMAIL PROTECTED]> (DG) wrote:

>DG> In article <[EMAIL PROTECTED]>,
>DG> Piet van Oostrum  <[EMAIL PROTECTED]> wrote:

>>> A more lightweight solution might be Ice. 
>>> It is architecturally similar to Corba, but with less overhead.

>DG> More lightweight and less overhead in what sense?  The performance
>DG> measurements I've seen show that Ice is significantly slower than many
>DG> CORBA implementations. If you mean more lightweight in terms of ease
>DG> of use, I don't see how. I quite agree that it's more lightweight in
>DG> terms of size of specification and difficulty for the ORB implementor,
>DG> but that's largely irrelevant to the users of the technology.

On http://www.zeroc.com/performance/ they compare it with TAO and it seems
to be faster. It looks also a bit simpler. I don't have experience with Ice
myself but a colleague of mine experimented with it and was enthousiastic.

It could well be that it is comparable in speed to omniORB, which is my
favorite platform for Corba on Python, or maybe even slower. Do you have
benchmark results about that?

But as I also said there is nothing wrong with using Corba, and the
advantage is that it is an established standard.
-- 
Piet van Oostrum <[EMAIL PROTECTED]>
URL: http://www.cs.uu.nl/~piet [PGP 8DAE142BE17999C4]
Private email: [EMAIL PROTECTED]
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Re: Confused about namespaces

[Bruno Desthuilliers]

KvS a écrit :
> Ok, makes sense but didn't seem "natural" to me, 

It will seem more natural if you understand that modules should be 
modulars (ie: low coupling, high cohesion). A module should *never* 
bother about no rely upon other modules being imported by the module it 
imports itself. Err, not quite clear... Let's rephrase it : a module 
should only used symbols it defines itself or that it *explicitely* 
imports from other modules.

> although it is an
> obvious consequence of what you just pointed out, namely that modules
> are evaluated in their own namespace, something to keep in mind... On
> the other hand it does apparently work recursively "the other way
> around" since I didn't explicitly import wx in main.py but only
> indirect via importing GUIclasses in which wx is imported right?

You've already got technical answers to this - please carefully (re)read 
Alex Martelli's post.

Now about coding style: this is *very* Bad Style(tm). Your main module 
imports should look like this:

import wx
# import settings -> we don't use the settings module here
from GUIclasses import KFrame

(...)

and the GUIclasses module's import :

import wx
import wx.lib.mixins.listctrl  as  listmix
import settings -> *here* we use the settings module

(...)

Python's philosophy is to favour readability.

Talking about imports, take time to open your Python interactive shell 
and type "import this" !-)

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Re: Immutable instances, constant values

[Steven D'Aprano]

On Fri, 18 Nov 2005 14:32:46 +1100, Ben Finney wrote:

> Is there any difference between a Python immutable value, and a
> constant? I suppose "constant" also implies that the *name* binds
> unchangeably to a particular value. Is that meaningful?

That's precisely how I understand "constant" to be useful. Consider:

c = 2.9979246e+08 # speed of light in metres per second

def energy(mass):
"""Converts mass in kilograms to energy in joules"""
return mass*c**2

That works fine until the name c is rebound to some other value. The fact
that the float object 2.9979246e+08 is immutable is necessary but not
sufficient.


> How does one actually ensure an object is immutable? Is it a matter of
> overriding a bunch of methods, or is ther a neater way?
> 
> Is it bad style to make a user-defined class that creates immutable
> objects? Why?

I can't see why it would be bad style. That's what FrozenSet does.

> In the case of 'enum', can anyone argue for or against an enumerated
> type being immutable? Its values being constant?

According to Gary Larson, there are four fundamental types of people. You
can tell them apart from their reaction to being given a half-filled glass:

"The glass is half full."

"The glass is half empty."

"Half full. No, half empty! No, half full. Wait... what was the question?"

"Hey! I ordered a cheeseburger!"

We might handle this with:

states = Enum("full", "empty", "indeterminate", "cheeseburger")

which then get referred to with:

states.full
states.empty
states.indeterminate
states.cheeseburger

I might decide that "argumentative" is a better label than "cheeseburger",
and mutate the appropriate enum value. What should happen? I see three
possibilities:

(1) states.cheeseburger still hangs around, but is not equivalent to
states.argumentative, in much the same way that reloading a module can
leave obsolete objects in your namespace (reloading doesn't automatically
cause names that point to objects from a module to rebind to new objects).

(2) references to states.cheeseburger raise an exception

(3) references to states.cheeseburger are equivalent to
states.argumentative. A rose by any other name. It shouldn't matter what
label we put on the enums, in principle.

Possibility (1) is obviously Bad with a Capital B, and should be avoided.

Possibility (2) has the saving grace that it is no different to what
happens if you rebind class attributes. There is an argument that if you
can rebind class attributes, you should be able to rebind enums and face
the consequences (good bad or indifferent) as best you can.

Possibility (3) is the logical solution. It shouldn't matter what labels
we put on the enums. But I fear not practical unless the enums are
implemented as Singletons (multitons?), and perhaps not even then. 

Alternatively, you could bypass the whole problem by making enums
immutable.


-- 
Steven.

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Re: Underscores in Python numbers

[Steven D'Aprano]

On Sat, 19 Nov 2005 01:33:40 -0800, bearophileHUGS wrote:

> Steven D'Aprano:
>> Perhaps Python should concatenate numeric literals at compile time:
>> 123 456 is the same as 123456.
> 
> I think using the underscore it is more explicit:
> n = 123_456

It is also easy to make a typo:

n = 123-456


-- 
Steven.

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what happens when the file begin read is too big for all lines to be read with "readlines()"

[Ross Reyes]

HI -
Sorry for maybe a too simple a question but I googled and also checked my 
reference O'Reilly Learning Python
book and I did not find a satisfactory answer.

When I use readlines, what happens if the number of lines is huge?I have 
a very big file (4GB) I want to
read in, but I'm sure there must be some limitation to readlines and I'd 
like to know how it is handled by python.
I am using it like this:
slines = infile.readlines() # reads all lines into a list of strings called 
"slines"

Thanks for anyone who knows the answer to this one. 
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Re: what happens when the file begin read is too big for all lines to be read with "readlines()"

[[EMAIL PROTECTED]]

newer python should use "for x in fh:", according to the doc :

fh = open("your file")
for x in fh: print x

which would only read one line at a time.

Ross Reyes wrote:
> HI -
> Sorry for maybe a too simple a question but I googled and also checked my
> reference O'Reilly Learning Python
> book and I did not find a satisfactory answer.
>
> When I use readlines, what happens if the number of lines is huge?I have
> a very big file (4GB) I want to
> read in, but I'm sure there must be some limitation to readlines and I'd
> like to know how it is handled by python.
> I am using it like this:
> slines = infile.readlines() # reads all lines into a list of strings called
> "slines"
> 
> Thanks for anyone who knows the answer to this one.

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Re: what happens when the file begin read is too big for all lines to be?read with "readlines()"

[Ben Finney]

Ross Reyes <[EMAIL PROTECTED]> wrote:
> Sorry for maybe a too simple a question but I googled and also
> checked my reference O'Reilly Learning Python book and I did not
> find a satisfactory answer.

The Python documentation is online, and it's good to get familiar with
it:

http://docs.python.org/>

It's even possible to tell Google to search only that site with
"site:docs.python.org" as a search term.

> When I use readlines, what happens if the number of lines is huge?
> I have a very big file (4GB) I want to read in, but I'm sure there
> must be some limitation to readlines and I'd like to know how it is
> handled by python.

The documentation on methods of the 'file' type describes the
'readlines' method, and addresses this concern.

http://docs.python.org/lib/bltin-file-objects.html#l2h-244>

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_o__)  |
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Re: Web-based client code execution

[David Wahler]

Steve wrote:
> AJAX works because browsers can execute javascript.  I don't know of a
> browser that can execute python.  Basically your stuck with java or
> javascript because everything else really isn't cross platform

Don't jump to conclusions...
http://dwahler.ky/python/

If you really, really want Python in a browser, it's certainly
possible. :)

-- David

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Re: Confused about namespaces

[KvS]

Thanks a lot for all the answers. After rereading everything said here
today it's become more clear to me what you guys are telling me and
I'll actively try to forget about "from ... import *" ;).

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Re: Python obfuscation

[Anton Vredegoor]

Alex Martelli wrote:

> Money is made in many ways, essentially by creating (perceived) buyer
> advantage and capturing some part of it -- but market segmentation is
> just one of many ways.  IF your predictions are ENORMOUSLY better than
> those the competition can make, then offering for free "slightly
> damaged" predictions, that are still better than the competition's
> despite the damage, MIGHT be a way to market your wares -- under a lot
> of other assumptions, e.g., that there is actual demand for the best
> predictions you can make, the ones you get paid for, so that your free
> service doesn't undermine your for-pay one.  It just seems unlikely that
> all of these preconditions would be satisfied at the same time; better
> to limit your "free" predictions along other axes, such as duration or
> location, which doesn't require your predictions' accuracy advantage to
> be ENORMOUS _and_ gives you a lot of control on "usefulness" of what
> you're supplying for free -- damaging the quality by randomization just
> seems to be unlikely to be the optimal strategy here, even if you had
> determined (or were willing to bet the firm that) marked segmentation is
> really the way to go here.

Suppose I grant all your theories about optimal marketing strategies.
This still doesn't account for the way the market is behaving *now*. It
isn't in any way logical or optimal. For example in Holland (where I
live) complete governmental departments are dedicated to make life
miserable for the unemployed, for asylum seekers, for people that
disagree with any official policy. If looking at the recent
developments in France I find it hard to believe that such social
inequality an injustice develops naturally. To me it looks more like
it's caused by organized crime, where *official* legal governmental
organizations are either crimimal organizations themselves or are
cooperating with such organizations.

You seem to tackle the problem of python obfuscation by first proving
that it isn't feasible and then giving some kind of solution that will
work and give the desired result: webservices. However when I look at
obfuscation techniques I see a desire to profit from giving some person
the idea that he or she is superior to someone else because he has a
better product. In order to avoid copying we now need obfuscation. The
difficulty to copy the thing (whether it is a swiss watch, a sportscar,
designer clothes, the latest computer game, an ipod, a computer
program) is part of the advertising game and is the basis for
associating it with a certain status. If you look for a few minutes at
a TV screen and notice what the commercials are trying to tell you, you
will see that it's almost always that you will be better, stronger,
more popular or beautyfull etc. if only you use product X.

You are perfectly right if you would say that it is an illogical
strategy to make people feel better relative to other people in order
to get them to do something you want. Commercial entities could in
principle be free of such things but we live in a world that is
dominated by this worldview and if one tries to sell something one has
to take that into account.

So how to get the same kind of market segmentation (as you call it)
when you deploy your program as a webservice and where essentially the
cost for you (moving a few electrons to produce a solution to a
problem) is exactly the same whether you give the user a good or a bad
result. If you give optimal results to everyone, users will go to other
sites just because these sites give them opportunity to feel better
than other people, not because this is objectively better, but just
because that is how they think the world "works".



> I hope this analogy clarifies why, while I don't think deliberate damage
> of result quality can be entirely ruled out, I think it's extremely
> unlikely to make any sense compared to ofher market segmentation
> tactics, even if you DO grant that it's worth segmenting (free samples
> are an extremely ancient and traditional tactic in all kind of food
> selling situations, after all, and when well-designed and promoting a
> product whose taste is indeed worth a premium price, they have been
> repeatedly shown to be potentially quite effective -- so, I'm hoping
> there will be no debate that the segmentation might perfectly well be
> appropriate for this "analogy" case, whether it is or isn't in the
> originally discussed case of selling predictions-via-webservices).

I agree it doesn't make sense. Like uncle Harry who thinks he can lay
golden eggs. We could cure him but we need the egss :-)

 Alternatively, lets just forget about obfuscation and try to get
people to freely share by promoting open source (and open webservices).

Anton

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Can you set a class instance's attributes to zero by setting the instance to zero?

[Gerard Flanagan]

Hello

If I have the Vector class below, is there a means by which I can have
the following behaviour


>>>A = Vector(1, 2)
>>>print A
(1, 2)
>>>A = 0
>>>print A
(0, 0)

If there is such a means, will it still work with the __slots__
attribution uncommented?

Thanks

class Vector(object):

#__slots__ = ('x', 'y')

def __init__(self, a=0, b=0 ):
self.x = a
self.y = b

def __repr__(self):
return '(%s, %s)' % (self.x, self.y)

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Re: Can you set a class instance's attributes to zero by setting the instance to zero?

[Diez B. Roggisch]

Gerard Flanagan wrote:
> Hello
> 
> If I have the Vector class below, is there a means by which I can have
> the following behaviour
> 
> 
> 
A = Vector(1, 2)
print A
> 
> (1, 2)
> 
A = 0
print A
> 
> (0, 0)
> 
> If there is such a means, will it still work with the __slots__
> attribution uncommented?

No, you can't. The reason is that python doesn't have an assignment 
operator as e.g. C++ has. The "=" just binds the name A to some object - 
without the object knowing it.

What's wrong with

class A:
def clear():
   pass
...

A.clear()

? Alternatively, you could try and abuse one of the seldom used in-place 
operator like __ior__:

A |= 0

But I wouldn't recommend that.

Regards,

Diez
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Re: Can you set a class instance's attributes to zero by setting theinstance to zero?

[Fredrik Lundh]

Gerard Flanagan wrote:

> If I have the Vector class below, is there a means by which I can have
> the following behaviour
>
A = Vector(1, 2)
print A
> (1, 2)

A = 0

that operation rebinds A; it doesn't affect the Vector instance in any way.

more here:

http://effbot.org/zone/python-objects.htm

 



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Re: what happens when the file begin read is too big for all lines to beread with "readlines()"

[Fredrik Lundh]

Ross Reyes wrote:

> When I use readlines, what happens if the number of lines is huge?I have
> a very big file (4GB) I want to read in, but I'm sure there must be some
> limitation to readlines and I'd like to know how it is handled by python.

readlines itself has no limitation, but it reads all the lines into memory, so
you'll probably run out of memory before the call returns.  Python raises
a MemoryError exception when this happens.

> I am using it like this:
> slines = infile.readlines() # reads all lines into a list of strings called
> "slines"

as others have pointed out, an iterator is the best way to solve this.
the iterator code will read blocks of data from the file, and return the
lines one by one.

if you need to support older versions of Python, xreadlines or repeated
calls to readlines(N) can be useful (see the third example on this page
for an example: http://effbot.org/zone/readline-performance.htm )

 



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Re: Immutable instances, constant values

[Bengt Richter]

On Sat, 19 Nov 2005 21:45:40 +1100, Steven D'Aprano <[EMAIL PROTECTED]> wrote:

>On Fri, 18 Nov 2005 14:32:46 +1100, Ben Finney wrote:
>
>> Is there any difference between a Python immutable value, and a
>> constant? I suppose "constant" also implies that the *name* binds
>> unchangeably to a particular value. Is that meaningful?
>
>That's precisely how I understand "constant" to be useful. Consider:
>
>c = 2.9979246e+08 # speed of light in metres per second
>
>def energy(mass):
>"""Converts mass in kilograms to energy in joules"""
>return mass*c**2
>
>That works fine until the name c is rebound to some other value. The fact
>that the float object 2.9979246e+08 is immutable is necessary but not
>sufficient.
>
>
>> How does one actually ensure an object is immutable? Is it a matter of
>> overriding a bunch of methods, or is ther a neater way?
>> 
>> Is it bad style to make a user-defined class that creates immutable
>> objects? Why?
>
>I can't see why it would be bad style. That's what FrozenSet does.
>
>> In the case of 'enum', can anyone argue for or against an enumerated
>> type being immutable? Its values being constant?
>
>According to Gary Larson, there are four fundamental types of people. You
>can tell them apart from their reaction to being given a half-filled glass:
>
>"The glass is half full."
>
>"The glass is half empty."
>
>"Half full. No, half empty! No, half full. Wait... what was the question?"
>
>"Hey! I ordered a cheeseburger!"
>
>We might handle this with:
>
>states = Enum("full", "empty", "indeterminate", "cheeseburger")
>
>which then get referred to with:
>
>states.full
>states.empty
>states.indeterminate
>states.cheeseburger
>
>I might decide that "argumentative" is a better label than "cheeseburger",
>and mutate the appropriate enum value. What should happen? I see three
>possibilities:
>
>(1) states.cheeseburger still hangs around, but is not equivalent to
>states.argumentative, in much the same way that reloading a module can
>leave obsolete objects in your namespace (reloading doesn't automatically
>cause names that point to objects from a module to rebind to new objects).
>
>(2) references to states.cheeseburger raise an exception
>
>(3) references to states.cheeseburger are equivalent to
>states.argumentative. A rose by any other name. It shouldn't matter what
>label we put on the enums, in principle.
>
>Possibility (1) is obviously Bad with a Capital B, and should be avoided.
>
>Possibility (2) has the saving grace that it is no different to what
>happens if you rebind class attributes. There is an argument that if you
>can rebind class attributes, you should be able to rebind enums and face
>the consequences (good bad or indifferent) as best you can.
>
>Possibility (3) is the logical solution. It shouldn't matter what labels
>we put on the enums. But I fear not practical unless the enums are
>implemented as Singletons (multitons?), and perhaps not even then. 
>
>Alternatively, you could bypass the whole problem by making enums
>immutable.
>
as in

 >>> from makeenum import makeEnum
 >>> states = makeEnum('states', 'full empty indeterminate cheeseburger')
 >>> for state in states: print repr(state)
 ...
 states.full
 states.empty
 states.indeterminate
 states.cheeseburger
 >>> for state in states: print state
 ...
 full
 empty
 indeterminate
 cheeseburger
 >>> states
 
 >>> states[1]
 states.empty
 >>> states['empty']
 states.empty
 >>> states[states.empty]
 states.empty
 >>> list(states)
 [states.full, states.empty, states.indeterminate, states.cheeseburger]
 >>> map(str, states)
 ['full', 'empty', 'indeterminate', 'cheeseburger']
 >>> len(states)
 4
 >>> states.full in states
 True
 >>> int(states.full)
 0
 >>> map(int, states)
 [0, 1, 2, 3]
 >>> 'ABC'[states.empty]
 'B'
 >>> states.empty == 1
 Traceback (most recent call last):
   File "", line 1, in ?
   File "makeenum.py", line 80, in __cmp__
 assert type(self)==type(other), (
 AssertionError: incompatible cmp types: states vs int

We can optionally make cmp work on int(self), int(other) for the enum...
 >>> states = makeEnum('states', 'full empty indeterminate cheeseburger', 
 >>> strict=int)
 >>> 'ABC'[states.empty]
 'B'
 >>> states.empty == 1
 True
 >>> type(states.empty)
 
 >>> a = list(states)
 >>> b = list(states)
 >>> [x is y for x,y in zip(a,b)]
 [True, True, True, True]
 >>> [x is y for x,y in zip(a,states)]
 [True, True, True, True]

(all the states are effectively singleton instances of the states class)
and immutable:

 >>> states.full = 'topped_off'
 Traceback (most recent call last):
   File "", line 1, in ?
   File "makeenum.py", line 34, in __setattr__
 raise AttributeError, '%s attributes may not be modified'%cls.__name__
 AttributeError: states attributes may not be modified
 >>> states.full.foo = 'trick'
 Traceback (most recent call last):
   File "", line 1, in ?
   File "makeenum.py", line 103, in __setattr__
 raise AttributeError, '%s instance attributes may not be set'% 
type(self)

Obtaining an member function by name

[guy lateur]

Hi all,

Suppose you have this class:

class foo:
def bar():

Suppose you also have the strings "foo" and "bar". How can you obtain the 
function foo.bar()?

Surely somebody knows..

TIA,
g


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Re: Obtaining an member function by name

[[EMAIL PROTECTED]]

f = getattr(obj,"bar")
f()

guy lateur wrote:
> Hi all,
>
> Suppose you have this class:
>
> class foo:
> def bar():
>
> Suppose you also have the strings "foo" and "bar". How can you obtain the
> function foo.bar()?
> 
> Surely somebody knows..
> 
> TIA,
> g

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Re: about try and exception

[Sybren Stuvel]

Bruno Desthuilliers enlightened us with:
> (Carl's top-post corrrected. Carl, please do not top-post)

If you correct people and ask them to alter their posting style, at
least make sure you post in a proper way. Snip what you're not
directly referring to, so people don't have to scroll in order to
start reading your post.

Sybren
-- 
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capital punishment for stupidity, but why don't we just take the
safety labels off of everything and let the problem solve itself? 
 Frank Zappa
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Re: Obtaining an member function by name

[Diez B. Roggisch]

guy lateur wrote:
> Hi all,
> 
> Suppose you have this class:
> 
> class foo:
> def bar():
> 
> Suppose you also have the strings "foo" and "bar". How can you obtain the 
> function foo.bar()?
> 
> Surely somebody knows..

getattr helps. However, your example won't work: it misses either a 
staticmethod-declaration, or a self-argument, or a classmethod and 
cls-argument. So unless we know if bar shall be an instance.method or 
not, it's hard to tell what exactly you want. Because you could want

getattr(getattr(mymodule, "foo"), "bar")

Or

getattr(getattr(mymodule, "foo")(), "bar")

(notice the parentheses)

or

getattr(getattr(locals(), "foo"), "bar")

or

getattr(getattr(globals(), "foo"), "bar")

Diez
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Re: Underscores in Python numbers

[Sybren Stuvel]

[EMAIL PROTECTED] enlightened us with:
> Of course, also support the locale variant where the meaning of ","
> and "." is swapped in most European countries.

This is exactly why I wouldn't use that notation. What happens if it
is hardcoded into the source? I mean, that's what we're talking about.
Then the program would have to have an indication of which locale is
used for which source file. Without that, a program would be
interpreted in a different way on different computers. I think that
would be rather messy.

I'm in favour of using spaces or underscores.

Sybren
-- 
The problem with the world is stupidity. Not saying there should be a
capital punishment for stupidity, but why don't we just take the
safety labels off of everything and let the problem solve itself? 
 Frank Zappa
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Re: Underscores in Python numbers

[[EMAIL PROTECTED]]

Sybren Stuvel wrote:
> [EMAIL PROTECTED] enlightened us with:
> > Of course, also support the locale variant where the meaning of ","
> > and "." is swapped in most European countries.
>
> This is exactly why I wouldn't use that notation. What happens if it
> is hardcoded into the source? I mean, that's what we're talking about.
> Then the program would have to have an indication of which locale is
> used for which source file. Without that, a program would be
> interpreted in a different way on different computers. I think that
> would be rather messy.
>
As mentioned in another post, we have that situation in all other
places. Such as

mm/dd/ vs dd/mm/
decimal("10.23") - would european people expect decimal("10,23") to
work ?
0x - a notation for base 16

why can't I have "E100.000,23" to mean "100,000.23" ? Nothing but
notation.

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Tkinter from Vis. BASIC

[Terrance N. Phillip]

In VB, an easy way I indicate progress is something like
do while 
lblNotify.foreground = randomcolor
 lblNotify.refresh   <---
 
  loop

I want to do the same thing in Python/Tkinter:

 # Wait for network to recognize the workstation:
 while os.system("slist") != 0:
 self.notify["fg"] = randcolor()
 # how do I refresh label l3 at this point?
 time.sleep(3)

I've tried self.notify.grid() (I'm using the grid geometry manager 
throughout), but that didn't work, and there is no redraw() or refresh() 
method that I can see.
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Re: PyQt layout question: QScrollView and QGridLayout?

[Volker Lenhardt]

Thank you Don, thank you David,

I was convinced that there must be a simple solution at hand. A dummy 
widget!

It does work to my needs. Don's ScrollToolView is very interesting 
though not yet the right tool for my actual application, but I've got 
some more ideas for long winter nights ...

All the best
Volker
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newbie-question about a list

[bobueland]

I've seen this construct in a script

>>> [x.capitalize() for x in ['a','b', 'c']]
['A', 'B', 'C']

I tried another myself

>>> [x+1 for x in [1,2,3]]
[2, 3, 4]
>>>

Apparently you can do
[function(x) for x in list]

I tried to find a description of this in "Library Reference" but
couldn't find it. Could somebody direct me where this type of construct
is described.

Bob

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Re: examining python objects

[rurpy]

Bruno Desthuilliers wrote:
> [EMAIL PROTECTED] a écrit :
> > Is there a function/class/module/whatever I can use to
> > look at objects?  I want something that will print the object's
> > value (if any) in pretty-printed form, and list all it's attributes
> > and their values.  And do all that recursively.
> > I want to be able to find out everything about an object that
> > Python can introspectively find out.
>
> Then check the inspect module

I want a callable, ready-to-use class or function.
Inspect provides soime funtions that would be useful for wrinting
such a class or function, but does not provide one.

I seems that nobody who has written or used such a tool reads
this group, or feels like responding.

FWIW, (for anyone looking for something similar in the future)
I found http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/137951
which will format and print an object's attributes.  By combining that
and pprint in the Python distrib, I think can coble up what I am
looking
for.

Still, it is discouraging that such a basic thing is not provided with
python, or at lleast easily available in some library.

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Re: examining python objects

[rurpy]

Bruno Desthuilliers wrote:
> [EMAIL PROTECTED] a écrit :
> > Is there a function/class/module/whatever I can use to
> > look at objects?  I want something that will print the object's
> > value (if any) in pretty-printed form, and list all it's attributes
> > and their values.  And do all that recursively.
> > I want to be able to find out everything about an object that
> > Python can introspectively find out.
>
> Then check the inspect module

I want a callable, ready-to-use class or function.
Inspect provides soime funtions that would be useful for wrinting
such a class or function, but does not provide one.

I seems that nobody who has written or used such a tool reads
this group, or feels like responding.

FWIW, (for anyone looking for something similar in the future)
I found http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/137951
which will format and print an object's attributes.  By combining that
and pprint in the Python distrib, I think can coble up what I am
looking
for.

Still, it is discouraging that such a basic thing is not provided with
python, or at lleast easily available in some library.

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Re: Obtaining an member function by name

[Bengt Richter]

On Sat, 19 Nov 2005 14:12:25 GMT, "guy lateur" <[EMAIL PROTECTED]> wrote:

>Hi all,
>
>Suppose you have this class:
>
>class foo:
>def bar():
>
>Suppose you also have the strings "foo" and "bar". How can you obtain the 
>function foo.bar()?
Why don't you type these things into an interactive python session
and see what happens? Also, foo.bar will be an unbound method of foo,
not a function per se. You could experiment a little, e.g.,

 >>> class foo:
 ... def bar():
 ...
   File "", line 3

 ^
 IndentationError: expected an indented block
 >>> class foo:
 ... def bar(): return 'bar is the name' # you could have done this
 ...
 >>> foo.bar()
 Traceback (most recent call last):
   File "", line 1, in ?
 TypeError: unbound method bar() must be called with foo instance as first 
argument (got nothing
 instead)
 >>> foo()
<__main__.foo instance at 0x02EF3D8C>
 >>> foo.bar(foo())
 Traceback (most recent call last):
   File "", line 1, in ?
 TypeError: bar() takes no arguments (1 given)
 >>> class foo:
 ... def bar(self): return self, 'bar is the name' # you could have done 
this
 ...
 >>> fooinst = foo()
 >>> fooinst
 <__main__.foo instance at 0x02EF756C>
 >>> foo.bar(fooinst)
 (<__main__.foo instance at 0x02EF756C>, 'bar is the name')
 >>> fooinst.bar
 >
 >>> fooinst.bar()
 (<__main__.foo instance at 0x02EF756C>, 'bar is the name')
 >>> foo.bar.im_func
 
 >>> foo.bar.im_func('first arg')
 ('first arg', 'bar is the name')
 >>> fooinst.bar
 >
 >>> fooinst.bar.im_func
 
 >>> fooinst.bar.im_func(1234)
 (1234, 'bar is the name')
 >>> fooinst.bar()
 (<__main__.foo instance at 0x02EF756C>, 'bar is the name')
 >>> foo.bar(333)
 Traceback (most recent call last):
   File "", line 1, in ?
 TypeError: unbound method bar() must be called with foo instance as first 
argument (got int inst
 ance instead)
 >>> foo.bar(fooinst)
 (<__main__.foo instance at 0x02EF756C>, 'bar is the name')

Someone can explain. If you do some of your own work, it will help even the 
load.
Have you looked at any documentation? Start at http://www.python.org/
and click a few things. There seems to be a beginners guide link under 
documentation
in the sidebar to the left ;-)

Regards,
Bengt Richter
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Re: newbie-question about a list

[bobueland]

This type of construct seems to be called "list comprehension".
Googling for

Python "list comprehension"

gives a lot of hints that describe the construct.

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Re: Underscores in Python numbers

[Roy Smith]

[EMAIL PROTECTED] wrote:
> Alternatively the underscore syntax may be used to separate the number
> from its base:
> 22875 == 22875_10 == 595b_16 == 123456_7
> But probably this is less commonly useful (and not much explicit).

We already have a perfectly good syntax for entering octal and hex 
integers, because those are commonly used in many applications.  There are, 
on occasion, need for other bases, but they are so rare, specialized, and 
non-standard (RFC-1924, for example, uses an interesting flavor of base-85) 
that having syntax built into the language to support them would be 
completely unjustified.
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Re: Tkinter from Vis. BASIC

[jmdeschamps]

Terrance N. Phillip wrote:
> In VB, an easy way I indicate progress is something like
>   do while 
>   lblNotify.foreground = randomcolor
>  lblNotify.refresh   <---
>  
>   loop
>
> I want to do the same thing in Python/Tkinter:
>
>  # Wait for network to recognize the workstation:
>  while os.system("slist") != 0:
>  self.notify["fg"] = randcolor()
>  # how do I refresh label l3 at this point?
>  time.sleep(3)
>
> I've tried self.notify.grid() (I'm using the grid geometry manager
> throughout), but that didn't work, and there is no redraw() or refresh()
> method that I can see.

I know of an update_idletask() method, look it up in the tkinter doc to
see if that's what you need!

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Re: Obtaining an member function by name

[EuGeNe]

guy lateur wrote:
> Hi all,
> 
> Suppose you have this class:
> 
> class foo:
> def bar():
> 
> Suppose you also have the strings "foo" and "bar". How can you obtain the 
> function foo.bar()?
> 
> Surely somebody knows..
> 
> TIA,
> g
> 
> 


Would that do?

 >>> class foo:
@staticmethod
def bar():
pass


 >>> foo.bar

 >>>
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Re: Obtaining an member function by name

[Bengt Richter]

On Sat, 19 Nov 2005 14:12:25 GMT, "guy lateur" <[EMAIL PROTECTED]> wrote:

>Hi all,
>
>Suppose you have this class:
>
>class foo:
>def bar():
>
>Suppose you also have the strings "foo" and "bar". How can you obtain the 
>function foo.bar()?
>
>Surely somebody knows..
>
Sorry, clean forgot about the strings.

 >>> class foo:
 ... def bar(self): return self, 'bar is the name'
 ...
 >>> # The definition is at global scope, so 'foo' will show up
 ... # in the globals() directory, which we can access with appended ['foo']
 ...
 >>> globals()['foo']
 
 >>> #if you want the 'bar' attribute using the string
 ... getattr(globals()['foo'], 'bar')
 
 >>> foo.bar
 

Note that getting an attribute does some "binding" magic if the
attribute has certain qualitites. In this case the bar function
is associated with the foo class to become an "unbound method"

Nit: usual convention is to spell class names with leading upper case.
Then you can e.g. use the lower case same name for an instance of the
class without confusions. Nit2: using new-style classes, which derive
from object (or also other bases, but at least object or type) is now
recommended, so you get the full-fledged attribute machinery that supports
much of the latest magic. So write the above more like

class Foo(object):
def bar(self): return self, 'bar is the name'

Regards,
Bengt Richter
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Re: Underscores in Python numbers

[Steve Holden]

[EMAIL PROTECTED] wrote:
> Stefan Rank wrote:
> 
>>The other idea of teaching int() about separator characters has
>>internationalis/zation issues:
>>In many European countries, one would naturally try::
>>
>>   int('500.000,23')
>>
>>instead of::
>>
>>   int('500,000.23')
> 
> 
> That is why I said
> 
> "Of course, also support the locale variant where the meaning of ","
> and
> "." is swapped in most European countries. "
> 
> We are seeing the same about base 2, 8, 10, 16.
> 
> May be :
> 
> int("E500.000,23")
> 
> as we are using :
> 
> 0x 
> 
> already for hex number
> 
I really wouldn't want it to become possible to write Python code in one 
locale that had to be edited before the numeric literals were valid in 
another locale. That way madness lies.

regards
  Steve
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PyCon TX 2006  www.python.org/pycon/

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Re: newbie-question about a list

[Bengt Richter]

On 19 Nov 2005 07:06:30 -0800, [EMAIL PROTECTED] wrote:

>I've seen this construct in a script
>
 [x.capitalize() for x in ['a','b', 'c']]
>['A', 'B', 'C']
>
>I tried another myself
>
 [x+1 for x in [1,2,3]]
>[2, 3, 4]

>
>Apparently you can do
>[function(x) for x in list]
>
>I tried to find a description of this in "Library Reference" but
>couldn't find it. Could somebody direct me where this type of construct
>is described.
>
It's called a list comprehension. You can find that term in various indices
of the various docs. In a minute I found these. I'm sure there's more if
you google.

http://docs.python.org/
http://docs.python.org/tut/node18.html#l2h-61
http://docs.python.org/ref/lists.html#l2h-345

Regards,
Bengt Richter
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Re: what happens when the file begin read is too big for all lines to be read with "readlines()"

[MrJean1]

Just try it, it is not that hard ... ;-)

/Jean Brouwers

PS) Here is what happens on Linux:

  $ limit vmemory 1
  $ python
  ...
  >>> s = file().readlines()
  Traceback (most recent call last):
File "", line 1 in ?
  MemoryError
  >>>

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Problems returning/attaching cookies

[john . lehmann]

Attacked is a piece of code which first hits the login page
successfully and receives back login cookies.  But then when I attempt
to hit a page which is restricted to logged in users only, I fail.

That seems to be because I am not successfully re-attaching the cookies
to the header portion of the this request.  I have tried 2 methods
which should both work I think.  The first was to use install_opener to
attach the cookie handler back to urlopen.  The second method was to
use the cookiehandler method add_cookie_header.  But in both cases,
before sending out the 2nd request, it seems to have empty headers --
which indicates to me that the necessary cookies have not been
attacked.

I also tryed messing with the policy quite a bit, thinking that might
be causing the cookies not to be returned.  First I used the default,
then set some flags on the default, then even overrode methods on the
default to make it as lenient as possible.  This had no apparent
effect.

Thanks a lot!

Below I have pasted the most relevant code section, as well as my full
code file.  Apologies for all the comments, but I wanted to show what I
had tried.
-
RELEVANT CODE (snipped from full code)

# NOW GO TO PAGE RESTRICTED TO LOGGED IN PEOPLE
the_url =
"http://www.dpreview.com/forums/login.asp?jump=editprofile.asp";
req = urllib2.Request(the_url)
#print "headers:", req.headers
#cj.add_cookie_header(req)

# EXPECT THESE HEADERS TO BE NON-EMPTY - BUT THEY ARE EMPTY,
# NO COOKIES RETURNED?
print "headers:", req.headers

# THIS OPEN FAILS - I GET - "NEED TO LOGIN" PAGE
#handle = opener.open(req)
handle = urllib2.urlopen(req)
the_page = handle.read()

-
FULL CODE

#!/usr/bin/python

import urllib
import urllib2
import re
import os
from cookielib import *

class MyCookiePolicy(DefaultCookiePolicy):
  def __init__(self):
DefaultCookiePolicy.__init__(self, rfc2965=True,
hide_cookie2=False, strict_ns_domain=DefaultCookiePolicy.DomainLiberal)
  def set_ok(self, cookie, request):
return True
  def return_ok(self, cookie, request):
return True
  def domain_return_ok(self, cookie, request):
return True
  def path_return_ok(self, cookie, request):
return True

the_url = 'http://www.dpreview.com/forums/login_post.asp'
user_agent = 'Mozilla/4.0 (compatible; MSIE 5.5; Windows NT)'
values = {
  'email' : '',
  'password' : '',
  #"remember" : "checked", # <- create permanent cookie
  'jump' : "/forums/"
  }
  # also "remember" : "remember"

# INITIAL REQUEST WITH USER INFO
headers = { 'User-Agent' : user_agent }
data = urllib.urlencode(values)
req = urllib2.Request(the_url, data, headers)

# COOKIE POLICY
# tried using several configurations of the default cookie policy
#policy = DefaultCookiePolicy(rfc2965=True, hide_cookie2=False,
strict_ns_domain=DefaultCookiePolicy.DomainLiberal)
# tried using my own custom cookie policy
#policy = MyCookiePolicy()
policy = DefaultCookiePolicy(rfc2965=True, hide_cookie2=False)

# CREATE COOKIE JAR WITH POLICY
cj = MozillaCookieJar()
cj.set_policy(policy)

# CREATE OPENER, AND OPEN PAGE
opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(cj))
urllib2.install_opener(opener)
#handle = opener.open(req)
handle = urllib2.urlopen(req)
the_page = handle.read()

# SHOW COOKIES COLLECTED - LOOKS GOOD HERE
for c in cj:
  print "COOKIE:", c
print "URL:", handle.geturl()
print "INFO:", handle.info()

#DEMONSTRATE WE'RE LOGGED IN
for line in the_page.split('\n'):
  line = line.strip()
  if re.search("Welcome to the", line):
print "MESSAGE:", line

# NOW GO TO PAGE RESTRICTED TO LOGGED IN PEOPLE
# - tried using the install_opener above
# - tried using add_cookie_header
# - either way, can't seem to get cookies in the header of this request
the_url =
"http://www.dpreview.com/forums/login.asp?jump=editprofile.asp";
req = urllib2.Request(the_url)
#print "headers:", req.headers
#cj.add_cookie_header(req)

# EXPECT THESE HEADERS TO BE NON-EMPTY
print "headers:", req.headers
#handle = opener.open(req)
handle = urllib2.urlopen(req)
the_page = handle.read()

# THIS ALSO PROVES LOGIN-STATE WAS LOST
for line in the_page.split('\n'):
  line = line.strip()
  if re.search("To access", line):
print "MESSAGE:", line

print "URL:", handle.geturl()
print "INFO:", handle.info()

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Using win32ui.CreateFileDialog() to get the name of a file.

[Joey C.]

Hello.
I'm writing a program that creates a series of batch operations to
convert movies to be used on iPodLinux.  The programs that do the
encoding and conversions are seperate from mine and all mine does is
use os.system() to call the program.

However, it needs to get an input file and an output file.  Originally
I was using just raw input, but I got adventuresome and decided to try
win32ui.CreateFileDialog().  But this will only open or save a file and
its output will be either 1 or a failure.  How might I go about using
it to get the _file name_ of a file.
For example.
Box appears asking user to find a file they want.  They double click on
the file.  Let's call it C:\Video.avi
Then another dialog box appears asking them where to save it.  They
save it at C:\iPodVideo.avi.

Now the Python program extracts the name of these files and then uses
os.system() to run:
mencoder.exe -[parameters] C:\Video.avi -o C:\iPodVideo.avi

Note that I'm not actually inputting the contents of the file, I'm just
passing the file name along.

How might I do this?  Thanks.

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Re: Obtaining an member function by name

[guy lateur]

Thanks for the feedback, people.

I actually only need the "bar" part (instance methods). I added the "foo" 
part to generalize the question without really thinking it through first. 
Still, it has gotten me more information than I ever imagined. So thanks 
again.

g 


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Re: deleting registry keys and value

[elbertlev]

Looks OK to me. Just tried on my network - works with no exceptions

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Is Python weak on the web side?

[Tony]

If I'd like to learn Python for web-development, what are the options 
available?

Thanks. tony
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Re: Is Python weak on the web side?

[Michael Goettsche]

On Sunday 20 November 2005 00:24, Tony wrote:
> If I'd like to learn Python for web-development, what are the options
> available?
>
> Thanks. tony

A nice framework is CherryPy: http://www.cherrypy.org
or Turbogears, which is based on CherryPy: http://www.turbogears.org/

Michael.
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Re: termios.tcgetattr(fd) error: (22, 'Invalid argument')

[Petr Jakes]

To provide  some feedback:
As Grant Edwards  posted in this list, I was running my code inside of
IDE that replaces sys.stdin with some other. While running the program
from a shell prompt, everything goes fine. 
Petr Jakes

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Re: Is Python weak on the web side?

[Gerard Flanagan]

Tony wrote:

> If I'd like to learn Python for web-development, what are the options
> available?
>
> Thanks. tony

Nov 18th:

http://groups.google.co.uk/group/comp.lang.python/browse_frm/thread/c23b12dc0edf8af0/19f859dc43c77ac1#19f859dc43c77ac1


Gerard

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Can a function access its own name?

[bobueland]

Look at the code below:

# mystringfunctions.py

def cap(s):
print s
print "the name of this function is " + "???"

cap ("hello")


Running the code above gives the following output

>>>
hello
the name of this function is ???
>>>

I would like the output to be

>>>
hello
the name of this function is cap
>>> 

Is that possible ?

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Re: Using win32ui.CreateFileDialog() to get the name of a file.

[Steve Holden]

Joey C. wrote:
> Hello.
> I'm writing a program that creates a series of batch operations to
> convert movies to be used on iPodLinux.  The programs that do the
> encoding and conversions are seperate from mine and all mine does is
> use os.system() to call the program.
> 
> However, it needs to get an input file and an output file.  Originally
> I was using just raw input, but I got adventuresome and decided to try
> win32ui.CreateFileDialog().  But this will only open or save a file and
> its output will be either 1 or a failure.  How might I go about using
> it to get the _file name_ of a file.
> For example.
> Box appears asking user to find a file they want.  They double click on
> the file.  Let's call it C:\Video.avi
> Then another dialog box appears asking them where to save it.  They
> save it at C:\iPodVideo.avi.
> 
> Now the Python program extracts the name of these files and then uses
> os.system() to run:
> mencoder.exe -[parameters] C:\Video.avi -o C:\iPodVideo.avi
> 
> Note that I'm not actually inputting the contents of the file, I'm just
> passing the file name along.
> 
> How might I do this?  Thanks.
> 
After you've had the user interact with the dialog you should call its 
GetFileName() method. The interactive interpreter can be useful in 
finding things like this out (though many details of objects can remain 
hidden in the Windows environment):

 >>> dir(d)
['GetFileExt', 'GetFileName', 'GetFileTitle', 'GetPathName', 
'GetPathNames', 'GetReadOnlyPref', 'SetOFNInitialDir', 'SetOFNTitle']
 >>> d.Show()

regards
  Steve
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Re: Underscores in Python numbers

[bearophileHUGS]

Roy Smith>We already have a perfectly good syntax for entering octal
and hex integers,

There is this syntax:
1536 == int("600", 16)
that accepts strings only, up to a base of 36.
There are the hex() and oct() functions.
There is the %x and %o sintax, that isn't easy to remember.
There are the 0x600 and 0600 syntaxes that probably look good only from
the point of view of a C programmer.
I think some cleaning up, with a simpler and more consistent and
general way of converting bases, can be positive. But probably no one
shares this point of view, and compatibility with C syntax is probably
positive, so you are right. I am still learning the correct way of
thinking in python.

Bye,
bearophile

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Re: Underscores in Python numbers

[Peter Hansen]

[EMAIL PROTECTED] wrote:
> Steven D'Aprano:
>>Perhaps Python should concatenate numeric literals at compile time:
>>123 456 is the same as 123456.
> 
> I think using the underscore it is more explicit:
> n = 123_456
> 
> Alternatively the underscore syntax may be used to separate the number
> from its base:
> 22875 == 22875_10 == 595b_16 == 123456_7
> But probably this is less commonly useful (and not much explicit).

Umm... in other words, "the underscore is under-used so let's assign 
some arbitrary meaning to it" (to make the language more like Perl 
perhaps?).

Or maybe one should instead interpret this as "numeric literals need 
more bells and whistles, and I don't care which of these two we add, but 
we have to do *something*!". :-)

-Peter
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Re: Can a function access its own name?

[Diez B. Roggisch]

[EMAIL PROTECTED] wrote:
> Look at the code below:
> 
> # mystringfunctions.py
> 
> def cap(s):
> print s
> print "the name of this function is " + "???"
> 
> cap ("hello")
> 
> 
> Running the code above gives the following output
> 
> >>>
> hello
> the name of this function is ???
> >>>
> 
> I would like the output to be
> 
> >>>
> hello
> the name of this function is cap
> >>> 
> 
> Is that possible ?

Yes, use the moduloe inspect to access the current stack frame:

def handle_stackframe_without_leak():
 frame = inspect.currentframe()
 try:
 print inspect.getframeinfo(frame)[2]
 finally:
 del frame



Diez
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Re: Can a function access its own name?

[Peter Hansen]

[EMAIL PROTECTED] wrote:
[edited slightly]
> def cap():
> print "the name of this function is " + "???"
> cap ()

sys._getframe() would help you here:

>>> import sys
>>> sys._getframe()

>>> def f():
...   global x
...   x = sys._getframe()
...
>>> f()
>>> x

>>> dir(x)
[..., 'f_builtins', 'f_code', 'f_exc_traceback', 'f_exc_type', ...]
>>> dir(x.f_code)
[...'co_name', 'co_names', 'co_nlocals', 'co_stacksize', 'co_varnames']
>>> x.f_code.co_name
'f'

So your function could be:

 >>> import sys
 >>> def cap():
...   print 'function name is', sys._getframe().f_code.co_name
...
 >>> cap()
function name is cap


-Peter
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Re: Can you set a class instance's attributes to zero by setting the instance to zero?

[Terry Hancock]

On 19 Nov 2005 05:29:07 -0800
"Gerard Flanagan" <[EMAIL PROTECTED]> wrote:
> If I have the Vector class below, is there a means by
> which I can have the following behaviour
> 
> 
> >>>A = Vector(1, 2)
> >>>print A
> (1, 2)
> >>>A = 0
> >>>print A
> (0, 0)

As has already been mentioned, "A = 0" rebinds the name "A"
to the object "0" so there's no way it can mutate the object
A.

However, you could create an object "Origin" to use as a
vector zero:

Origin = Vector(0,0)

Or if you want to be shorter, more poetic, and make future
maintainers curse you, you can call it "O":

O = Vector(0,0)

;-)

-- 
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Anansi Spaceworks http://www.AnansiSpaceworks.com

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Re: Tkinter from Vis. BASIC

[Terrance N. Phillip]

[EMAIL PROTECTED] wrote:

>>I want to do the same thing in Python/Tkinter:
>>
>> # Wait for network to recognize the workstation:
>> while os.system("slist") != 0:
>> self.notify["fg"] = randcolor()
>> # how do I refresh label l3 at this point?
>> time.sleep(3)

> I know of an update_idletask() method, look it up in the tkinter doc to
> see if that's what you need!
> 
Thanks. I did a dir(label_object) and saw update() and 
update_idletasks(). updeate() seems to do the trick.
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Re: textwrap.dedent() drops tabs - bug or feature?

[Steven Bethard]

Peter Hansen wrote:
> Steven Bethard wrote:
> 
>> Note that even though the tabs are internal, they are still removed by 
>> textwrap.dedent().  The documentation[1] says:
> 
> ...
> 
>> So it looks to me like even if this is a "feature" it is undocumented. 
>> I'm planning on filing a bug report, but I wanted to check here first 
>> in case I'm just smoking something.
> 
> While I wouldn't say it's obvious, I believe it is (indirectly?) 
> documented and deliberate.
> 
> Search for this in the docs:
> """
> expand_tabs
> (default: True) If true, then all tab characters in text will be 
> expanded to spaces using the expandtabs() method of text.
> """

Thanks for double-checking this for me.  I looked at expand_tabs, and 
it's part of the definition of the TextWrapper class, which is not 
actually used by textwrap.dedent().  So I think the textwrap.dedent() 
expanding-of-tabs behavior is still basically undocumented.

I looked at the source code, and the culprit is the first line of the 
function definition:

 lines = text.expandtabs().split('\n')

I filed a bug_ report, but left the Category unassigned so that someone 
else can decide whether it's a doc bug or a code bug.

STeVe

.. _bug: http://python.org/sf/1361643
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Re: Can a function access its own name?

[bobueland]

Thanks Diez and Peter,

Just what I was looking for. In "Library Reference" heading

3.11.1 Types and members

I found the info about the method you described. I also made a little
function to print out not just the name of the function but also the
parameter list. Here it is

# fname.py
import sys, string

def cap(s, n):
  print string.replace("".join([sys._getframe().f_code.co_name, \
repr(sys._getframe().f_code.co_varnames)]), "\'", "")

cap('Hello', 'Bob')

Running this yields the result

cap(s, n)

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Re: Underscores in Python numbers

[[EMAIL PROTECTED]]

Steve Holden wrote:
> [EMAIL PROTECTED] wrote:
> > Stefan Rank wrote:
> >
> >>The other idea of teaching int() about separator characters has
> >>internationalis/zation issues:
> >>In many European countries, one would naturally try::
> >>
> >>   int('500.000,23')
> >>
> >>instead of::
> >>
> >>   int('500,000.23')
> >
> >
> > That is why I said
> >
> > "Of course, also support the locale variant where the meaning of ","
> > and
> > "." is swapped in most European countries. "
> >
> > We are seeing the same about base 2, 8, 10, 16.
> >
> > May be :
> >
> > int("E500.000,23")
> >
> > as we are using :
> >
> > 0x
> >
> > already for hex number
> >
> I really wouldn't want it to become possible to write Python code in one
> locale that had to be edited before the numeric literals were valid in
> another locale. That way madness lies.
That is the fact, from the very beginning. 1.234 striaightly speaking
can have different meaning,. So if you don't want, don't support it and
always use the non-European notation.

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Re: Problems returning/attaching cookies

[john . lehmann]

NEVERMIND.  My friend pointed out that I am simply hitting the wrong
URL when trying to "test" whether I am logged in or not.  The correct
one is:  http://www.dpreview.com/forums/editprofile.asp

But I still have one question, if anyone knows -- why is it that when I
print out the headers on my request object, they are empty?  I thought
that I should find the cookies there which are being sent back.  This
is what I thought the problem was.  Thanks if anyone can explain how
that works.

John

(PS i have stopped attacking the cookies now)


[EMAIL PROTECTED] wrote:
> Attacked is a piece of code which first hits the login page
> successfully and receives back login cookies.  But then when I attempt
> to hit a page which is restricted to logged in users only, I fail.
>
> That seems to be because I am not successfully re-attaching the cookies
> to the header portion of the this request.  I have tried 2 methods
> which should both work I think.  The first was to use install_opener to
> attach the cookie handler back to urlopen.  The second method was to
> use the cookiehandler method add_cookie_header.  But in both cases,
> before sending out the 2nd request, it seems to have empty headers --
> which indicates to me that the necessary cookies have not been
> attacked.
>
> I also tryed messing with the policy quite a bit, thinking that might
> be causing the cookies not to be returned.  First I used the default,
> then set some flags on the default, then even overrode methods on the
> default to make it as lenient as possible.  This had no apparent
> effect.
>
> Thanks a lot!
>
> Below I have pasted the most relevant code section, as well as my full
> code file.  Apologies for all the comments, but I wanted to show what I
> had tried.
> -
> RELEVANT CODE (snipped from full code)
>
> # NOW GO TO PAGE RESTRICTED TO LOGGED IN PEOPLE
> the_url =
> "http://www.dpreview.com/forums/login.asp?jump=editprofile.asp";
> req = urllib2.Request(the_url)
> #print "headers:", req.headers
> #cj.add_cookie_header(req)
>
> # EXPECT THESE HEADERS TO BE NON-EMPTY - BUT THEY ARE EMPTY,
> # NO COOKIES RETURNED?
> print "headers:", req.headers
>
> # THIS OPEN FAILS - I GET - "NEED TO LOGIN" PAGE
> #handle = opener.open(req)
> handle = urllib2.urlopen(req)
> the_page = handle.read()
>
> -
> FULL CODE
>
> #!/usr/bin/python
>
> import urllib
> import urllib2
> import re
> import os
> from cookielib import *
>
> class MyCookiePolicy(DefaultCookiePolicy):
>   def __init__(self):
> DefaultCookiePolicy.__init__(self, rfc2965=True,
> hide_cookie2=False, strict_ns_domain=DefaultCookiePolicy.DomainLiberal)
>   def set_ok(self, cookie, request):
> return True
>   def return_ok(self, cookie, request):
> return True
>   def domain_return_ok(self, cookie, request):
> return True
>   def path_return_ok(self, cookie, request):
> return True
>
> the_url = 'http://www.dpreview.com/forums/login_post.asp'
> user_agent = 'Mozilla/4.0 (compatible; MSIE 5.5; Windows NT)'
> values = {
>   'email' : '',
>   'password' : '',
>   #"remember" : "checked", # <- create permanent cookie
>   'jump' : "/forums/"
>   }
>   # also "remember" : "remember"
>
> # INITIAL REQUEST WITH USER INFO
> headers = { 'User-Agent' : user_agent }
> data = urllib.urlencode(values)
> req = urllib2.Request(the_url, data, headers)
>
> # COOKIE POLICY
> # tried using several configurations of the default cookie policy
> #policy = DefaultCookiePolicy(rfc2965=True, hide_cookie2=False,
> strict_ns_domain=DefaultCookiePolicy.DomainLiberal)
> # tried using my own custom cookie policy
> #policy = MyCookiePolicy()
> policy = DefaultCookiePolicy(rfc2965=True, hide_cookie2=False)
>
> # CREATE COOKIE JAR WITH POLICY
> cj = MozillaCookieJar()
> cj.set_policy(policy)
>
> # CREATE OPENER, AND OPEN PAGE
> opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(cj))
> urllib2.install_opener(opener)
> #handle = opener.open(req)
> handle = urllib2.urlopen(req)
> the_page = handle.read()
>
> # SHOW COOKIES COLLECTED - LOOKS GOOD HERE
> for c in cj:
>   print "COOKIE:", c
> print "URL:", handle.geturl()
> print "INFO:", handle.info()
>
> #DEMONSTRATE WE'RE LOGGED IN
> for line in the_page.split('\n'):
>   line = line.strip()
>   if re.search("Welcome to the", line):
> print "MESSAGE:", line
>
> # NOW GO TO PAGE RESTRICTED TO LOGGED IN PEOPLE
> # - tried using the install_opener above
> # - tried using add_cookie_header
> # - either way, can't seem to get cookies in the header of this request
> the_url =
> "http://www.dpreview.com/forums/login.asp?jump=editprofile.asp";
> req = urllib2.Request(the_url)
> #print "headers:", req.headers
> #cj.add_cookie_header(req)
>
> # EXPECT THESE HEADERS TO BE NON-EMPTY
> print "headers:", req.headers
> #handle = opener.open(req)
> handle = urllib2.urlopen(req)
> the_page = handle.read()
>
> # THIS ALSO PROVES LOGIN-STATE WAS LOST
> for line in the_page.split('\n

Re: Speeding up multiple regex matches

[Talin]

OK that worked really well. In particular, the "lastindex" property of
the match object can be used to tell exactly which group matched,
without having to sequentially search the list of groups.

In fact, I was able to use your idea to cobble together a poor man's
lexer which I am calling "reflex" (Regular Expressions For Lexing).
Here's an example of how it's used:

# Define the states using an enumeration
State = Enum( 'Default', 'Comment', 'String' )

# Create a scanner
scanner = reflex.scanner( State.Default )
scanner.rule( "\s+" )
scanner.rule( "/\*", reflex.set_state( State.Comment ) )
scanner.rule( "[a-zA-Z_][\w_]*", KeywordOrIdent )
scanner.rule( "0x[\da-fA-F]+|\d+", token=TokenType.Integer )
scanner.rule(
"(?:\d+\.\d*|\.\d+)(?:[eE]?[+-]?\d+)|\d+[eE]?[+-]?\d+",
token=TokenType.Real )

# Multi-line comment state
scanner.state( State.Comment )
scanner.rule( "\*/", reflex.set_state( State.Default ) )
scanner.rule( "(?:[^*]|\*(?!/))+" )

# Now, create an instance of the scanner
token_stream = scanner( input_file_iter )
for token in token_stream:
print token

Internally, it creates an array of patterns and actions for each state.
Then when you ask it to create a scanner instance, it combines all of
the patterns into a large regular expression. Input lines are marched
vs. this regex, and if a match succeeds, then the match object's
'lastindenx' property is used to look up the actions to perform in the
array.

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Re: Using win32ui.CreateFileDialog() to get the name of a file.

[Joey C.]

Okay, thank you.  This worked very well.

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Re: HTML generation vs PSP vs Templating Engines

[riplin]

> No templates, no python-like or special languages, only pure and simple 
> python.

> You can embedd python into html or, if it better suits your programming
> style, you can embed html into python. Why don't you give it a try?

I dislike embedding code or html in each other, apart from the
'impurity' of mixing code and user interface it makes them inseparable.

Using templates means that the code can work with different templates,
and this should be seamless, it also means that different code can be
used with the templates, for example if different languages are used.

The main advantage, for me, is that different outputs formats can be
created without changing the code. If the user wants a set of data in a
table then the html template is used, if they want a csv file of the
data, that is just a different template name.  A printed report: same
code just a different template name. XML, simple text, postscript,
EDIFACT file, all done with same code, different template. Just arrange
for the name of the template file to be a parameter on the URL and the
various outputs can be selected by the user.

I did, however, write my own templating module, they are quite easy to
do.

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Re: Behaviour of enumerated types

[Ben Finney]

Bengt Richter <[EMAIL PROTECTED]> wrote:
> On Sat, 19 Nov 2005 11:10:42 +1100 (EST), Ben Finney <[EMAIL PROTECTED]> 
> wrote:
> >Bengt Richter <[EMAIL PROTECTED]> wrote:
> >> If [an enumeration has a fixed sequence], what is more natural
> >> than using their index values as keys to other ordered info?
> >I don't see why. If you want sequence numbers, use enumerate(). If
> >not, the enum object itself can be used directly as an iterable.
>
> I changed mine so the enum _class_ is iterable, but enum instances
> are not.

I'm not really understanding your design.

In my enum package, an enumeration is an instance of Enum. Those
instances are iterable, producing EnumValue instances; the EnumValue
instances are also available as named attributes of the Enum instance.

>>> from enum import Enum
>>> colours = Enum('red', 'blue', 'green')
>>> for val in colours:
... print str(val)
...
red
blue
green

Why would the Enum *class* be iterable?

> >> OTOH, the index values (and hence my enums) are[1] not very good
> >> as unique dict keys, since they compare[2] promiscuously with
> >> each other and other number types.
> >Indeed, that's why (in my design) the values from the enum are only
> >useful for comparing with each other. This, to me, seems to be the
> >purpose of an enumerated type.
>
> Have you tried yet to use two different enum instances as keys in
> the same dict?

What do you mean by "enum instances"? I presume you mean "values from
a single enum".

>>> colour_german = { colours.red: "rot", colours.green: "grün",
>>> colours.blue: "blau" }
>>> for val in colours:
... print colour_german[val]
...
rot
blau
grün

> Then try to sort the keys(or items is the values are misc different
> enums).

Oh, perhaps you mean "enum values from different enum instances". No,
those won't compare against each other; there's no meaningful
relationship, since different enum instances are conceptually
different types.

> I hit that, and changed __cmp__ to compare (typename,  other if not int subtype>) tuples.

I think this is a flaw, based on expecting too strong a relationship
between the enum value instance, and an integer value.

> That sorts items grouped by enum type if they're keys.

Why should colours.blue compare before fruits.orange? How is that
meaningful?

> >I think I've addressed all your current concerns; I don't believe
> >an inherent correlation to integers is necessary at all.
> 
> Necessary wasn't the question for me. It's whether it's desirable.
> YMMV ;-)

I'm still trying to understand what is served by having some exposed
relationship between an enum value instance and an integer value.

> >It's no more necessary than saying that ["a", "b", "c"] requires
> >that there be some specific correlation between the values of that
> >list and the integers 0, 1, 2. If you *want* such a correlation, in
> >some particular case, use enumerate() to get it; but there's
> >nothing about the values themselves that requires that
> >correspondence.
>
> Yet it is comforting to know that ['a', 'b', 'c'][0] will interpret
> the [0] to mean the first in the sequence (unless someone is doing a
> list-like repr trick based on some other type ;-).

Again, you're only talking about *sequence*, not correspondence to
integers. Your case above isn't an argument in favour of "the 'a'
value should coerce to the 0 value". Why then should an enum value
instance coerce to any particular integer value?

> The class methods are introduced via metaclass in the makeEnum factory
> and it's a very hacky workaround for the fact that execution of a
> class definition body only has local and module global namespace, so
> you can't directly reference anything local to the factory function.

Here you've lost me, since I don't understand why you want
enumerations to be classes at all. Are you going to be making
instances of an entire enumeration? If not, why make classes instead
of objects?

-- 
 \ "The illiterate of the future will not be the person who cannot |
  `\ read. It will be the person who does not know how to learn."  |
_o__) -- Alvin Toffler |
Ben Finney
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Re: Underscores in Python numbers

[Steve Holden]

[EMAIL PROTECTED] wrote:
> Steve Holden wrote:
[...]
>>I really wouldn't want it to become possible to write Python code in one
>>locale that had to be edited before the numeric literals were valid in
>>another locale. That way madness lies.
> 
> That is the fact, from the very beginning. 1.234 striaightly speaking
> can have different meaning,. So if you don't want, don't support it and
> always use the non-European notation.
> 

Being European myself I am well aware of the notational differences of 
the different locales, and I am perfectly happy that users can enter 
numbers in their preferred format when they execute a program.

However, I am not happy about the idea that a program source would need 
to be edited before it would work after being moved to another locale.

regards
  Steve
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PyCon TX 2006  www.python.org/pycon/

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Re: Immutable instances, constant values

[Ben Finney]

Steven D'Aprano <[EMAIL PROTECTED]> wrote:
> On Fri, 18 Nov 2005 14:32:46 +1100, Ben Finney wrote:
> > Is there any difference between a Python immutable value, and a
> > constant? I suppose "constant" also implies that the *name* binds
> > unchangeably to a particular value. Is that meaningful?
> 
> That's precisely how I understand "constant" to be useful.

The Python docs don't really talk about such a thing. However, the
None name cannot be re-bound. Is that all that's required to have a
"constant" in Python?

If so, it's part of the assignment statement, and not something the
object itself can decide. True?

> > How does one actually ensure an object is immutable? Is it a
> > matter of overriding a bunch of methods, or is ther a neater way?

Really hoping someone can come up with an answer for this.

> > Is it bad style to make a user-defined class that creates
> > immutable objects? Why?
> 
> I can't see why it would be bad style. That's what FrozenSet does.

"from foo import *" is supported in the language, but is still bad
style. FrozenSet was *added* to the language (2.2), so that's evidence
that Guido thinks it's a good idea. But I'd still like direct
discussion: is making one's class instances immutable bad style?

-- 
 \  "Say what you will about the Ten Commandments, you must always |
  `\ come back to the pleasant fact that there are only ten of |
_o__)  them."  -- Henry L. Mencken |
Ben Finney
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Re: textwrap.dedent() drops tabs - bug or feature?

[Peter Hansen]

Steven Bethard wrote:
> Thanks for double-checking this for me.  I looked at expand_tabs, and 
> it's part of the definition of the TextWrapper class, which is not 
> actually used by textwrap.dedent().  So I think the textwrap.dedent() 
> expanding-of-tabs behavior is still basically undocumented.

Ah, good point.  I saw dedent() in there with the wrap() and fill() 
convenience functions which use a TextWrapper internally, but you're 
quite right that dedent() is different, and in fact merely uses the 
expandtabs() functionality of the standard string class, so this has 
nothing to do with the expand_tabs attribute I pointed out.

-Peter
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Re: HTML generation vs PSP vs Templating Engines

[Luis M. Gonzalez]

I meant that it is not strictly necessary to use templates in
Karrigell, although you can use Cheetah if you want.
I'm not used to templates mainly because I'm familiar with the way PHP
works and, for simple dynamic sites like those I work on, this is the
simpliest approach.
Another reason is that I'm a little bit lazy for learning yet another
language, be it a python-like one or a template one.

Also, I feel that Python is easy enough for having to resort to another
language.
I usually create my pages with Dreamweaver or any other visual tool,
and once the design is ready, I add a few python lines to it which,
combined with modules that are separated from the html code, work
wonders on my sites.

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Re: searching for files on Windows with Python

[Kent Johnson]

Peter Hansen wrote:
> Kent Johnson wrote:
>> import path
>> files = path.path(pathToSearch).walkfiles(filename)
> 
> A minor enhancement (IMHO) (though I certainly agree with Kent's 
> recommendation here): since there is nothing else of interest in the 
> "path" module, it seems to be a fairly common idiom to do "from path 
> import path" and skip the doubled "path.path" bit.

Certainly it's your choice. I find most programs using path only reference 
path.path once, to create a starting path; other paths are created from that 
using files() or / etc. In this case it is less typing to say

import path
basePath = path.path(...)

instead of

from path import path
basePath = path(...)

from path import path only wins on number of chars if you reference path 
*three* times.

YMMV :-)

Kent
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Re: Is there a way to create a button in either pygame or livewires?

[Lee Harr]

> Is there a way to create a button in either pygame or livewires, that is 
> able to be clicked and when clicked sends a command to restart the program?
>


You could try something like this using pygsear
(http://www.nongnu.org/pygsear/)

The button can call either start() which just makes
a new Game instance in the same process, or
full_restart() which starts a new process and quits
the current one.



from pygsear import Game, Widget
from pygsear.locals import RED


class G(Game.Game):
def initialize(self):
print 'starting up...'

self.button = Widget.SpriteTextButton(self.window, "Restart",
size=40, color=RED, padding=20)
self.events.add(self.button.events)
self.button.set_callback(self.restart)
self.button.set_position((200, 100))
self.sprites.add(self.button)

def restart(self, ev):
print 'restarting...'
#start()
full_restart()
self.quit = True



def start():
g = G()
g.mainloop()


def full_restart():
import os
import sys
cmd = 'python %s &' % sys.argv[0]
os.system(cmd)


if __name__ == '__main__':
start()

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Re: HTML generation vs PSP vs Templating Engines

[has]

[EMAIL PROTECTED] wrote:
> I dislike embedding code or html in each other, apart from the
> 'impurity' of mixing code and user interface it makes them inseparable.
>
> Using templates means that the code can work with different templates,
> and this should be seamless, it also means that different code can be
> used with the templates, for example if different languages are used.

This seems to contradict your statement that you dislike 'embedding
code or html in each other', since the scenarios you describe still
involve embedding presentation logic in markup. (The only templating
systems that *completely* separate logic from markup are the DOM-style
ones.)

I assume what you really meant is that you don't like embedding *model*
logic in markup, which is generally good design practice. However,
templating systems that use Python for presentation logic (Karrigell,
PSP, Nevow, HTMLTemplate, etc) certainly don't force you to put model
logic into the template; you are quite entitled to keep that separate
as per MVC. They just don't *enforce* the model logic/presentation
logic separation as some authoritarian custom language-based systems
do.

HTH

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Re: path module / class

[Neil Hodgson]

Peter Hansen:

> Compelling to whom?  I wonder if it's even possible for Guido to find 
> compelling anything which obsoletes much of os.path and shutil and 
> friends (modules which Guido probably added first and has used the most 
> and feels most comfortable with).

To me, most uses of path.py are small incremental improvements over 
os.path rather than being compelling. Do a number of small improvements 
add up to be large enough to make this change?  There is a cost to the 
change as there will be two libraries that have to be known to 
understand code. Does someone have an example application that moved to 
path.py with a decrease in errors or noticeable decrease in complexity? 
Could all path manipulation code be switched or is coverage incomplete?

The duplication argument should be answered by looking at all the 
relevant modules and finding a coherent set of features that work with 
path.py without overlap so that the obsolete methods can be deprecated. 
If adding path.py leads to a fuzzy overlapping situation where os.path 
is occasionally useful then we are complicating the user's life rather 
than simplifying it.

Neil
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Re: Underscores in Python numbers

[Steven D'Aprano]

On Sat, 19 Nov 2005 13:08:57 -0500, Peter Hansen wrote:

> Umm... in other words, "the underscore is under-used so let's assign 
> some arbitrary meaning to it" (to make the language more like Perl 
> perhaps?).

+1

I *really* don't like the idea of allowing underscores in numeric
literals. Firstly, for aesthetic reasons: I think 123_456 is seriously
ugly. Secondly, for pragmatic reasons, I think it is too easy to mistype
as 123-456. I know that Python can't protect you from typing 9-1 instead
of 901, but why add special syntax that makes that sort of error MORE
common?)

> Or maybe one should instead interpret this as "numeric literals need 
> more bells and whistles, and I don't care which of these two we add, but 
> we have to do *something*!". :-)

-1

That's a tad unfair. Dealing with numeric literals with lots of digits is
a real (if not earth-shattering) human interface problem: it is hard for
people to parse long numeric strings. In the wider world outside of IT,
people deal with long numeric digits by grouping. This is *exceedingly*
common: mathematicians do it, economists do it, everybody who handles long
numeric literals does it *except* computer language designers.

Depending on personal preference and context, we use any of comma, period,
dash or space as a separator. Underscore is never used. Of these, the
comma clashes with tuples, the period opens a rather large can of worms
vis-a-vis internationalisation, and the dash clashes with the minus sign.
Allowing spaces to group digits is subtle but effective, doesn't clash
with other syntax, and is analogous to string concatenation.

I don't believe it is either practical or desirable for a computer
language to accept every conceivable digit separator in literals. If you
need full support for internationalised numbers, that should go into a
function. But the question of including a digit separator for numeric
literals does solve a real problem, it isn't just meaningless bells and
whistles.

Likewise, base conversion into arbitrary bases is not, in my opinion,
common enough a task that support for it needs to be built into the syntax
for literals. If somebody cares enough about it, write a module to handle
it and try to get it included with the Python standard modules.


-- 
Steven.

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Re: Underscores in Python numbers

[Steve Holden]

Steven D'Aprano wrote:
[...]
> Likewise, base conversion into arbitrary bases is not, in my opinion,
> common enough a task that support for it needs to be built into the syntax
> for literals. If somebody cares enough about it, write a module to handle
> it and try to get it included with the Python standard modules.
> 
In fact Icon managed to offer a syntax that allowed every base up to 36 
to be used: an "r" was used to indicate the radix of the literal, so hex 
453FF would be represented as "16r453FF". This worked fine. Upper- and 
lower-case letters werw regarded as equivalent.

regards
  Steve
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Holden Web LLC www.holdenweb.com
PyCon TX 2006  www.python.org/pycon/

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Re: Underscores in Python numbers

[[EMAIL PROTECTED]]

Steve Holden wrote:
> Being European myself I am well aware of the notational differences of
> the different locales, and I am perfectly happy that users can enter
> numbers in their preferred format when they execute a program.
>
> However, I am not happy about the idea that a program source would need
> to be edited before it would work after being moved to another locale.
>
Huh ?

Up to now, all I am talking about is making the three init
function(int/float/decimal) to be smarter on coverting string to their
type. It doesn't affect the code in anyway if you don't need it or want
to use it. It is more like a helper function for the issue of people
are so concern about the seperators in big numbers. It introduce no new
syntax to the language at all. And should you say use the imaginary
format "E500.000,23", it still works no matter where your program is
running or what the hosting locale is. Don't understand what changes
you are referring to.

We are facing similar issue today. A typical case is MM/DD/ date
format. Or may be I need to import text file(csv for example) which may
already contain numbers in this format.

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Re: Underscores in Python numbers

[[EMAIL PROTECTED]]

Steven D'Aprano wrote:
> That's a tad unfair. Dealing with numeric literals with lots of digits is
> a real (if not earth-shattering) human interface problem: it is hard for
> people to parse long numeric strings. In the wider world outside of IT,
> people deal with long numeric digits by grouping. This is *exceedingly*
> common: mathematicians do it, economists do it, everybody who handles long
> numeric literals does it *except* computer language designers.
However, what is the percentage of these big number literals appears in
source code ? I believe most of them either appears in some data
file(thus is nothing but string) or during data input(again string).
Why change the language when we just want a smarter string converter ?

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Re: Immutable instances, constant values

[Steven D'Aprano]

On Sun, 20 Nov 2005 08:56:33 +1100, Ben Finney wrote:

> Steven D'Aprano <[EMAIL PROTECTED]> wrote:
>> On Fri, 18 Nov 2005 14:32:46 +1100, Ben Finney wrote:
>> > Is there any difference between a Python immutable value, and a
>> > constant? I suppose "constant" also implies that the *name* binds
>> > unchangeably to a particular value. Is that meaningful?
>> 
>> That's precisely how I understand "constant" to be useful.
> 
> The Python docs don't really talk about such a thing. However, the
> None name cannot be re-bound. Is that all that's required to have a
> "constant" in Python?

I think None is a special case. The docs have said that None will become
a keyword in the future.

> If so, it's part of the assignment statement, and not something the
> object itself can decide. True?

Yes, that would be how I interpret constants: You want a name which can't
be re-bound to something else.

One work-around is to use the convention of writing the name in all caps:

CONSTANT = some_value

and then trust that your module user doesn't rebind CONSTANT. I'd like to
see support for something a little stronger than just "cross your fingers
and hope", without necessarily going all the way to Pascal's full
enforcement of constants. "We're all adults here" -- if somebody *really*
wants to rebind CONSTANT, I'm not going to stop them, but I want them to
jump through a hoop to do it, as a reminder that the module creator thinks
they shouldn't be doing it.

The obvious analogy is with name mangling of __private attributes in
classes. 


>> > How does one actually ensure an object is immutable? Is it a matter
>> > of overriding a bunch of methods, or is ther a neater way?
> 
> Really hoping someone can come up with an answer for this.

So am I :-)

Have you looked at the source for Frozenset? It was a pure Python module
in Python 2.3, before becoming a built-in in 2.4.



-- 
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PATH environment variable

[mirandacascade]

O/S: Win2K
Vsn of Python:2.4

Based on a search of other posts in this group, it appears as though
os.environ['PATH'] is one way to obtain the PATH environment variable.

My questions:
1) is it correct that os.environ['PATH'] contains the PATH environment
variable?
2) are there other ways to obtain the PATH environment variable? if so,
is one way of obtaining the PATH environment variable preferable to
another way?

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Re: Underscores in Python numbers

[Steven D'Aprano]

On Sun, 20 Nov 2005 01:39:04 +, Steve Holden wrote:

> Steven D'Aprano wrote:
> [...]
>> Likewise, base conversion into arbitrary bases is not, in my opinion,
>> common enough a task that support for it needs to be built into the syntax
>> for literals. If somebody cares enough about it, write a module to handle
>> it and try to get it included with the Python standard modules.
>> 
> In fact Icon managed to offer a syntax that allowed every base up to 36 
> to be used: an "r" was used to indicate the radix of the literal, so hex 
> 453FF would be represented as "16r453FF". This worked fine. Upper- and 
> lower-case letters werw regarded as equivalent.

Forth goes significantly further than that: you can tell the Forth
interpreter what base you are using, and all numbers are then read and
displayed using that base. Numbers were case sensitive, which meant Forth
understood bases to at least 62. I don't remember whether it allows
non-alphanumeric digits, and therefore higher bases -- I think it does,
but am not sure.

Nevertheless, I don't believe that sort of functionality belongs in the
language itself. It is all well and good to be able to write 32r37gm, but
how often do you really need to write numbers in base 32?



-- 
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Re: Behaviour of enumerated types

[Bengt Richter]

On Sun, 20 Nov 2005 08:42:48 +1100 (EST), Ben Finney <[EMAIL PROTECTED]> wrote:

>Bengt Richter <[EMAIL PROTECTED]> wrote:
>> On Sat, 19 Nov 2005 11:10:42 +1100 (EST), Ben Finney <[EMAIL PROTECTED]> 
>> wrote:
>> >Bengt Richter <[EMAIL PROTECTED]> wrote:
>> >> If [an enumeration has a fixed sequence], what is more natural
>> >> than using their index values as keys to other ordered info?
>> >I don't see why. If you want sequence numbers, use enumerate(). If
>> >not, the enum object itself can be used directly as an iterable.
>>
>> I changed mine so the enum _class_ is iterable, but enum instances
>> are not.
>
>I'm not really understanding your design.
>
>In my enum package, an enumeration is an instance of Enum. Those
>instances are iterable, producing EnumValue instances; the EnumValue
>instances are also available as named attributes of the Enum instance.
I have a similar situation, except I have an enum factory function makeEnum
instead of a class Enum, and the factory returns not an instance of Enum,
but an enum as a unique type, i.e., a class. But it is functionally analogous,
except I differentiate by
>
>>>> from enum import Enum
>>>> colours = Enum('red', 'blue', 'green')
>>>> for val in colours:
>... print str(val)
>...
>red
>blue
>green
>
That corresponds to

 >>> from makeenum import makeEnum
 >>> Colours = makeEnum('Colours', 'red blue green')
 >>> for val in Colours:
 ... print str(val),'-(repr)->', repr(val)
 ...
 red -(repr)-> Colours.red
 blue -(repr)-> Colours.blue
 green -(repr)-> Colours.green

I added the repr to show that the vals were instances of something,
and they are actuall instances of the Colours type, which was uniquely
created to represent the enumeration, along with its fixed set of internally
cached immutable instances, references to which are returned by the Colours
constructor (__new__) instead of creating potentially duplicate instances.
So these instances can serve as sentinels too. The id's don't change, no
matter how many you construct (of a given member of the instance set). Of
course there are len(Colours) fixed (once created and cached) instances
of Colours in all.

 >>> list(Colours)
 [Colours.red, Colours.blue, Colours.green]
 >>> map(str, Colours)
 ['red', 'blue', 'green']
 >>> map(int, Colours)
 [0, 1, 2]
 >>> int(Colours.blue)
 1
 >>> Colours[1]
 Colours.blue


>Why would the Enum *class* be iterable?
That corresponds to asking why my makeEnum should be iterable,
and the it is not. What makeEnum makes functionally corresponds
to your Enum instance, except my "instance" is a unique manufactured class.
>
>> >> OTOH, the index values (and hence my enums) are[1] not very good
>> >> as unique dict keys, since they compare[2] promiscuously with
>> >> each other and other number types.
>> >Indeed, that's why (in my design) the values from the enum are only
>> >useful for comparing with each other. This, to me, seems to be the
>> >purpose of an enumerated type.
>>
>> Have you tried yet to use two different enum instances as keys in
>> the same dict?
>
>What do you mean by "enum instances"? I presume you mean "values from
>a single enum".
Yes, by analogy to your functionality, but since my "single enum" is
actually a class returned by makeEnum, not an instance of Enum, i.e.,

 >>> Colours
 

and the "values" are immutable singleton instances that you can access via
the class (which I gave some unusual capabilities -- i.e., some methods
that apply to it as an ordered collection of immutable instances, and
which aren't accessible as methods of the instances (though the instances
have special methods of their own, and inherit methods from int).

>
>>>> colour_german = { colours.red: "rot", colours.green: "grün",
>>>> colours.blue: "blau" }
>>>> for val in colours:
>... print colour_german[val]
>...
>rot
>blau
>grün
That's a plain dict with colour "values" as keys. Same as (checking the order 
first
to get the zip correspondence right ;-)

 >>> list(Colours)
 [Colours.red, Colours.blue, Colours.green]


 >>> colour_german = dict(zip(Colours, ('rot', 'blau', 'grün')))
 >>> for val in Colours:
 ... print 'colour_german[%r] => %s' %(val, colour_german[val])
 ...
 colour_german[Colours.red] => rot
 colour_german[Colours.blue] => blau
 colour_german[Colours.green] => grün


>
>> Then try to sort the keys(or items is the values are misc different
>> enums).
>
>Oh, perhaps you mean "enum values from different enum instances". No,
Yes, again by analogy.
>those won't compare against each other; there's no meaningful
>relationship, since different enum instances are conceptually
>different types.
Well, yes, I made that the strict default cmp, but I can optionally make
"Enum instances" (makeEnum returned classes) whose values cmp differently.
But now that I think of it, sorting is pretty controllable anyway, e.g,
suppose we had a Coins enum:

 >>> Coins = makeEnum('Coins', 'penny nickel dime quarter')
 

Re: How to write an API for a Python application?

[Cameron Laird]

In article <[EMAIL PROTECTED]>, I mumbled:
.
.
.
>Pyro might be perfect.  My own instinct is to start even more
>primitively, with a minimal asynchat client and server.  I've
>looked through the *Cookbook*, and see that it doesn't have
>what I want.  Maybe it's time Phaseit donate one of the
>little models we use ...  

Ah-ha!  See Example 19-7, on page 447 of *Python in a Nutshell*:
under two dozen lines that provide an echo server which correctly
handles multiple concurrent clients.  

But that's also about as much as I've found publicly in that 
direction.  The original questioner wanted, or thought he wanted,
an object-capable protocol, so he could invoke methods remotely;
for that, I return to Paul Boddie's correct observation that 
folks can use CORBA, or imitate CORBA badly (as much of this
season's "SOA" does).  What I don't see, though, is a nice client-
server pair that are minimal, and exhibit *symmetric* event-oriented
performance and scalability.  Some people mistakenly regard this
"peering" architecture as a dark secret.  I think I'll write a model
in under fifty lines of Python this week ...
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Re: Underscores in Python numbers

[Peter Hansen]

Steven D'Aprano wrote:
> Dealing with numeric literals with lots of digits is
> a real (if not earth-shattering) human interface problem: it is hard for
> people to parse long numeric strings.

I'm totally unconvinced that this _is_ a real problem, if we define 
"real" as being even enough to jiggle my mouse, let alone shattering the 
planet.

What examples does anyone have of where it is necessary to define a 
large number of large numeric literals?  Isn't it the case that other 
than the odd constants in various programs, defining a large number of 
such values would be better done by creating a data file and parsing it?

And if that's the case, one could easily define any convention one 
desired for formatting the raw data.

And for the odd constant, either take a moment to verify the value, or 
define it in parts (e.g. 24*60*60*1000*1000 microseconds per day), or 
write a nice little variant on int() that can do exactly what you would 
have done for the external data file if you had more values.

-Peter
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Re: Python obfuscation

[Alex Martelli]

Anton Vredegoor <[EMAIL PROTECTED]> wrote:
   ...
> Suppose I grant all your theories about optimal marketing strategies.
> This still doesn't account for the way the market is behaving *now*. It
> isn't in any way logical or optimal. For example in Holland (where I
> live) complete governmental departments are dedicated to make life

What makes you think that governmental departments are part of the
*market*?!  Government behavior is controlled by laws that are vastly
different from those controlling market behavior; if you're interested,
you could study the "theory of public choice".

Studying "perfect" markets (which can be mathematically proven to be
optimal in some senses -- the Arrow-Debreu Model, for example) is
parallel to studying physical systems that do not have attrition or
other such complications -- it's mathematically sharp (not easy, but WAY
easier than taking account of all the complications of the real world),
intellectually fascinating, AND practically useful in many (not all)
cases, since many real systems can be usefully modeled as "perfect" ones
with "perturbations" (second-order effects) considered separately.

If Galileo had tried to START physics by studying real-world systems in
all of their complexity, we'd still be at square zero; fortunately, he
was able to identify systems "close enough to perfect" (e.g., heavy
weights faling to the ground, compact enough to ignore air resistance,
etc) to get the ball rolling.  Physics still faces a lot of challenges
after many centuries in areas where the "perturbations" are much
stronger than "second-order" -- I'm told our physical modeling of cloud
systems or such everyday phenomena as welding is still way from perfect,
for example (forget quantum and relativistic effects... I'm talking of
everyday observations!-), and of course so does the much younger
discipline of mathematical economics.  Nevertheless the study of the
"perturbations" is well under way, with Nobel memorial prizes having
already been awarded in such fields as "bounded rationality" and
asymmetric-information markets.

Just like a gunner in the mid-19th century had to know fundamental
physics pretty well, but also developed experience-based heuristics to
compensate for all of the "perturbations" in his system, so the
practicing economic actor today needs a mix of science and art (in the
original meaning of "art", of course).


> You seem to tackle the problem of python obfuscation by first proving
> that it isn't feasible and then giving some kind of solution that will
> work and give the desired result: webservices. However when I look at

That seems to me to be a practicable technical approach, yes.

> obfuscation techniques I see a desire to profit from giving some person
> the idea that he or she is superior to someone else because he has a
> better product. In order to avoid copying we now need obfuscation. The

You're discussing the *motivation* for obfuscating, while what I was
giving was a possible way of *implementing* similar effects.

> difficulty to copy the thing (whether it is a swiss watch, a sportscar,
> designer clothes, the latest computer game, an ipod, a computer
> program) is part of the advertising game and is the basis for
> associating it with a certain status. If you look for a few minutes at

Yes, this is close to the theory of luxury goods (which is WAY
underdeveloped, by the way: if you're a post-doctoral student in
economics and are wondering where best to direct your research in order
to stand a chance to gain a Nobel memorial prize some day, you could do
worse than turn your efforts to this field).  The maths are complicated,
in the theory of luxury goods, because utility is RELATIVE: buyer's
advantage cannot be computed, even theoretically, from knowing just the
buyer's utility curve and the amount of good supplied to that buyer,
because the curve depends on the *relative* amounts supplied to that
buyer versus other buyers.

Throw asymmetric information into the mix, and, besides a mathematically
unmanageable mess, you get the famous anomaly whereby an INCREASE i the
price may locally result in an INCREASE in demand (backwards-sloping
price-demand curve) -- each buyer, lacking information about other
buyers, infers it from price signals, and *assumes* (as is normally the
case) that higher price means fewer buyers; since fewer buyers means a
higher relative advantage, this assumption increases each buyer's
appetite and thus, in the aggregate, raises demand.

While this is fascinating as an open research topic, AND crucial to
economic survival for purveyors of luxury good, I dispute the wisdom of
trying to model MOST markets of interest as subject to the fascinating
complications of "luxury goods theory".

Take, again, the specific example of the sawmill with NC saws, doing
custom work by cutting customer-specified shapes out of standard planks
of wood.  If things can be optimized, so that six such shapes can be cut
out of each plant rather than

Re: path module / class

[Peter Hansen]

Neil Hodgson wrote:
>To me, most uses of path.py are small incremental improvements over 
> os.path rather than being compelling. Do a number of small improvements 
> add up to be large enough to make this change?  

If the number of small improvements is large enough then, as with other 
such situations in the world, the overall change can definitely become 
qualitative.  For me that's the case with using path.py.

> There is a cost to the 
> change as there will be two libraries that have to be known to 
> understand code. 

Could you please clarify?  Which two do you mean?

> Does someone have an example application that moved to 
> path.py with a decrease in errors or noticeable decrease in complexity? 

We've mandated use of path.py internally for all projects because we've 
noticed (especially with non-expert Python programmers... i.e. junior 
and intermediate types, and senior types new to Python) a decrease in 
errors.  Adoption of the appropriate methods in path.py (e.g. 
joinpath(), .name and .ext, .files()) is higher than the use of the 
equivalent methods or idioms with the standard libraries.  How to do 
something, if not immediately obvious, is easier to discover because the 
docs and code are all in one place (for path.py).

There's certainly a noticeable decrease in complexity.  I could 
elaborate, but I honestly believe that this should be obvious to anyone 
who has seen almost any of the examples that have been posted, where a 
dozen lines of regular Python collapse to half that with path.py.  Just 
removing imports of os, shutil, fnmatch, and glob in favour of a single 
one makes things "noticeably" (though admittedly not hugely) less complex.

> Could all path manipulation code be switched or is coverage incomplete?

As far as I can tell with our own usage, it is complete.  We have not 
yet written code that required falling back to one of the existing 
modules, though I certainly wouldn't be shocked if someone had examples.

>The duplication argument should be answered by looking at all the 
> relevant modules and finding a coherent set of features that work with 
> path.py without overlap so that the obsolete methods can be deprecated. 
> If adding path.py leads to a fuzzy overlapping situation where os.path 
> is occasionally useful then we are complicating the user's life rather 
> than simplifying it.

I agree with that, but don't believe it is the case.  And if one or two 
minor examples exist, fixing those cases would make more sense to me 
than abandoning the entire idea.

For the record, though, if I haven't said it before, it doesn't really 
bother me that this isn't part of the standard library.  I find it 
trivial to install in site-packages for all our workstations, and as we 
deliver code with py2exe it comes along for the ride.  (And I feel no 
particular personal need to make things a lot simpler for newcomers to 
the language (other than those who work with me), though for people who 
do feel that need I definitely promote the idea of path.py becoming 
standard.)

-Peter
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Re: How to write an API for a Python application?

[Alex Martelli]

Cameron Laird <[EMAIL PROTECTED]> wrote:

> In article <[EMAIL PROTECTED]>, I mumbled:
>   .
>   .
>   .
> >Pyro might be perfect.  My own instinct is to start even more
> >primitively, with a minimal asynchat client and server.  I've
> >looked through the *Cookbook*, and see that it doesn't have
> >what I want.  Maybe it's time Phaseit donate one of the
> >little models we use ...  
> 
> Ah-ha!  See Example 19-7, on page 447 of *Python in a Nutshell*:
> under two dozen lines that provide an echo server which correctly
> handles multiple concurrent clients.  

Note also that you can freely download all of the code in my book as
http://examples.oreilly.com/pythonian/pythonian-examples.zip (it's just
36 KB).  In that same chapter you will find several implementations of
mutually compatible clients and servers for that same echo-oid
"protocol" (as well as one incompatible one using UDP -- all the others
use TCP).  I hope they can be useful to anybody wanting to kludge
together some simple TCP/IP thingy (though, for the problem being
discussed in this thread, I'd rather recommend Corba;-).


Alex
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Re: Confused about namespaces

[Alex Martelli]

KvS <[EMAIL PROTECTED]> wrote:

> Thanks a lot for all the answers. After rereading everything said here
> today it's become more clear to me what you guys are telling me and
> I'll actively try to forget about "from ... import *" ;).

I commend you for your decision.  It's a construct that I sometimes find
quite handy in an experimentation session in the interactive
interpreter, but just has no really good place in 'true' code;-0.


Alex

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Re: what happens when the file begin read is too big for all lines to be read with "readlines()"

[Xiao Jianfeng]

[EMAIL PROTECTED] wrote:

>newer python should use "for x in fh:", according to the doc :
>
>fh = open("your file")
>for x in fh: print x
>
>which would only read one line at a time.
>
>  
>
 I have some other questions:

 when "fh" will be closed?

 And what shoud I do if I want to explicitly close the file immediately 
after reading all data I want?

>Ross Reyes wrote:
>  
>
>>HI -
>>Sorry for maybe a too simple a question but I googled and also checked my
>>reference O'Reilly Learning Python
>>book and I did not find a satisfactory answer.
>>
>>When I use readlines, what happens if the number of lines is huge?I have
>>a very big file (4GB) I want to
>>read in, but I'm sure there must be some limitation to readlines and I'd
>>like to know how it is handled by python.
>>I am using it like this:
>>slines = infile.readlines() # reads all lines into a list of strings called
>>"slines"
>>
>>Thanks for anyone who knows the answer to this one.
>>
>>
>
>  
>

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Re: Underscores in Python numbers

[Roy Smith]

Steven D'Aprano <[EMAIL PROTECTED]> wrote:
> That's a tad unfair. Dealing with numeric literals with lots of digits is
> a real (if not earth-shattering) human interface problem: it is hard for
> people to parse long numeric strings. 

There are plenty of ways to make numeric literals easier to read without 
resorting to built-in language support.  One way is:

sixTrillion = 6 * 1000 * 1000 * 1000 * 1000

Or, a more general solution might be to write a little factory function 
which took a string, stripped out the underscores (or spaces, or commas, or 
whatever bit of punctuation turned you on), and then converted the 
remaining digit string to an integer.  You could then write:

creditCardNumber = myInt ("1234 5678 9012 3456 789")

Perhaps not as convenient as having it built into the language, but 
workable in those cases which justify the effort.
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exception raised by nested iterator being ignored by for loop

[james t kirk]

I'm writing a wrapper class to handle the line merging and filtering
for a log file analysis app

The problem I'm running into is that the StopIteration exception
raised when the wrapped file goes past EOF isn't causing the second
for loop to stop. Wrapping the second for loop in a try/except clause
shows that the exception is being raised though. 

Could someone more familiar with the underlying implementation please
give me a hint as to why this is happening?


import gzip
class wrapper :

def __init__ (self, filename) :
if filename[-3:] == ".gz" :
self.fh = gzip.GzipFile(filename, "r")
else :
self.fh = open(filename, "r")

def __iter__ (self) :
return self

def next (self) :
for line in self.fh :   # StopIteration raised here when
file exhausted
if line[:1] == "t" :# filter out lines starting with
't'
continue
return line.rstrip()

if __name__ == "__main__" :
# using the file handle
fh = open("test.txt")
for line in fh :
print line.rstrip()
fh.close()

# using the wrapper class
fh = wrapper("test.txt")
for line in fh :# StopIteration ignored here
print line

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Re: Can a function access its own name?

[B Mahoney]

Decorate any function with @aboutme(), which
will print the function name each time the function is called.

All the 'hello' stuff is in the aboutme() decorator code.
There is no code in the decorated functions themselves
doing anything to telling us the function name.


# The decorator
def aboutme():

def thecall(f, *args, **kwargs):
# Gets to here during module load of each decorated function

def wrapper( *args, **kwargs):
# Our closure, executed when the decorated function is called
print "Hello\nthe name of this function is '%s'\n" \
% f.func_name
return f(*args, **kwargs)

return wrapper

return thecall

@aboutme()
def testing(s):
print "string '%s' is argument for function" % s


@aboutme()
def truing():
return True

# Try these 
testing('x')

testing('again')

truing()

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query domain registry from python?

[randomtalk]

hi, does anyone know of a library that can query domain registry or any
site that provide information to such an activity? as i want to build a
simple domain name searching program for my own benefit.. thanks alot :D

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Re: Hot to split string literals that will across two or more lines ?

[Mike Meyer]

Steven D'Aprano <[EMAIL PROTECTED]> writes:
> Brackets include:
>
> parentheses or round brackets ( )
> square brackets [ ]
> braces or curly brackets { }
> chevrons or angle brackets 〈 〉
>
> The symbols for chevrons are not available on common keyboards, are not
> available in ordinary ASCII, and may not show up correctly in many
> typefaces, so a common alternative is to substitute less than and greater
> than signs < > as brackets. HTML and XML use that convention.

Hmm. I'm used to seeing "angle brackets" - aka brokets - used to refer
to . That may be the convention you mention leaking across, though.

You imply that HTML/XML might use chevrons. I don't think that's the
case. They inherit their start/end tag characters from SGML's
default.

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Re: what happens when the file begin read is too big for all lines to be read with "readlines()"

[Steven D'Aprano]

On Sun, 20 Nov 2005 11:05:53 +0800, Xiao Jianfeng wrote:

>  I have some other questions:
> 
>  when "fh" will be closed?

When all references to the file are no longer in scope:

def handle_file(name):
fp = file(name, "r")
# reference to file now in scope
do_stuff(fp)
return fp


f = handle_file("myfile.txt)
# reference to file is now in scope
f = None
# reference to file is no longer in scope

At this point, Python *may* close the file. CPython currently closes the
file as soon as all references are out of scope. JPython does not -- it
will close the file eventually, but you can't guarantee when.

>  And what shoud I do if I want to explicitly close the file immediately 
> after reading all data I want?

That is the best practice.

f.close()


-- 
Steven.

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Re: Underscores in Python numbers

[Mike Meyer]

Steven D'Aprano <[EMAIL PROTECTED]> writes:
> On Sat, 19 Nov 2005 13:08:57 -0500, Peter Hansen wrote:
>> Umm... in other words, "the underscore is under-used so let's assign 
>> some arbitrary meaning to it" (to make the language more like Perl 
>> perhaps?).
>
> +1
>
> I *really* don't like the idea of allowing underscores in numeric
> literals. Firstly, for aesthetic reasons: I think 123_456 is seriously
> ugly. Secondly, for pragmatic reasons, I think it is too easy to mistype
> as 123-456. I know that Python can't protect you from typing 9-1 instead
> of 901, but why add special syntax that makes that sort of error MORE
> common?)

I've seen at least one language (forget which one) that allowed such
separators, but only for groups of three. So 123_456 would be valid,
but 9_1 would be a syntax error. This kind of thing might help with
the detecting typos issue, and probably won't be noticed by most
users.

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Delays getting data on sys.stdin.readline() ?

[Christian Convey]

Hello,

I've got a program that (ideally) perpetually monitors sys.stdin for
lines of text. As soon as a line comes in, my program takes some
action.

The problem is, it seems like a very large amount of data must
accumulate on sys.stdin before even my first invocation of readline()
returns.  This delay prevents my program from being responsive in the
way it must be.

Has anyone else seen this effect?  If so, is there a reasonable workaround?

Thanks very much,
Christian
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Re: Underscores in Python numbers

[Roy Smith]

Mike Meyer <[EMAIL PROTECTED]> wrote:
> I've seen at least one language (forget which one) that allowed such
> separators, but only for groups of three.

That seems a bit silly.  Not all numbers are naturally split into groups of 
three.  Credit card numbers are (typically) split into groups of four.  
Account numbers are often split into all sorts of random groupings.
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