date:20091118

During the last few days I have written code in support of a small DDL
language that encapsulates a concise representation of the
manipulations needed to make a deep subcopy of a Python-like data
structure. It is inspired by syntax from mainstream modern languages,
including, of course, Python. The DDL can be converted to an AST. That
AST can be walked to either generate Python code that expresses the
mapping or to generate Python objects that can execute the mapping.
Either of the prior outputs can then subsequently be applied to real
world inputs to create new Python data structures from old ones, using
the mechanisms specified in the original DDL for attribute access,
dictionary lookup, iteration, method invocation, etc.

Here is an example of the DDL (and I hate the terminology DDL, just
cannot think of anything better):


{
'show_table_of_contents',
'author' {
.person 'name',
.person 'location' as city,
.favorite_books()[
.title,
.cost() as expense
] as books}
}


There are more details here:

http://showellonprogramming.blogspot.com/2009/11/more-on-python-deep-copy-schema.html

Apart from shamelessly plugging my blog, I am hoping to generate
ideas, constructive criticism, etc.

Feel free to comment here or on the blog.  So far there are three
entries on the blog, all pertaining to Python.

The implementation of the idea is quite new, but it is a topic that I
have been pondering for a long time--no matter how expressive your
programming language of choice might be, there are certain programming
tasks that just seem needlessly tedious.  The mini-language above
proposes to solve one problem but solve it well.

I am particularly interested to find out whether somebody has tried
something like this before.





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Re: IOError: [Errno 28] No space left on device

2009-11-18 Thread Diez B. Roggisch


Lie Ryan schrieb:

hong zhang wrote:


--- On Tue, 11/17/09, Tim Chase python.l...@tim.thechases.com wrote:


From: Tim Chase python.l...@tim.thechases.com
Subject: Re: IOError: [Errno 28] No space left on device
To: Lie Ryan lie.1...@gmail.com
Cc: python-list@python.org
Date: Tuesday, November 17, 2009, 7:47 PM

for i in

glob.glob('/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx'):

with open(i, 'w') as f:
print
f, cont_tx

work perfectly.

But following get error like:
print f, cont_tx
IOError: [Errno 28] No space left on device

Apparently the harddisk where you stored the file is

full?

Likely a misinterpretation of the error.  I'm guessing
either one needs to be root to write to this [likely
virtual] file, or a member of an associated group..  It
would help to have the output of

bash$ whoami
bash$ id

and

bash$ ls -lsF
/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx


It is root. see following.
  File ../henry-cont-tx, line 186, in do_cont_tx
print f, cont_tx
IOError: [Errno 28] No space left on device
r...@tester-laptop:/home/tester/Desktop/sv-project/scripts/scripts# 
whoami

root
r...@tester-laptop:/home/tester/Desktop/sv-project/scripts/scripts# id
uid=0(root) gid=0(root) groups=0(root)
r...@tester-laptop:/home/tester/Desktop/sv-project/scripts/scripts# ls 
-lsF /sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx
0 -rw--- 1 root root 0 2009-11-17 17:51 
/sys/kernel/debug/ieee80211/phy2/iwlagn/data/continuous_tx




Where is the output file? Could it possibly be located in a device that 
is impossible to write even for root (e.g. filesystem mounted as 
read-only or CD or floppy with the readonly switch active or NTFS 
partition without ntfs-3g driver)?


Can you write to this file from outside python (try echo-ing to the 
file)? What's the permission of the folder?


The output of your 'df' shows that you only have one partition (for 
root) and nothing else; it is quite uncommon for linux/unix to be setup 
with only one partition, you didn't trim anything right?


/sys is not a block-device, it's similar to /proc (or replaces it, I 
forgot). It displays system-information and device-trees and whatnot, 
and some of those files can be written to change settings.


I think the error the OP sees is a mis-interpretion or unlucky re-map of 
an error-code the kernel gives when things go wrong, I can only guess 
but maybe he writes to fast to the files, or to often.



Diez
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Re: XML root node attributes

2009-11-18 Thread Slafs

Thanks

But this doesn't work. I've ended using something like this:

import xml.etree.ElementTree as ET
root = ET.Element(root, dict(a='v', b='v2', c='v3'))
n = ET.SubElement(root,'d')
tree = ET.ElementTree(root)
import sys
tree.write(sys.stdout)


On 17 Lis, 15:36, Stefan Behnel stefan...@behnel.de wrote:
 Slafs, 17.11.2009 15:19:

  I'm little confused about adding attributes to the root node when
  creating an XML document.
  Can I do this using minidom or something else.

 Yes, you /can/, but you /should/ use something else.

  I can't find anything that would fit my needs.

  i would like to have something like this:
  ?xml ... ?
  root a=v b=v2 c=v3
      d ...  /d
     
  /root

 Use ElementTree:

     import xml.etree.ElementTree as ET
     root = ET.Element(root, dict(a='v', b='v2', c='v3'))
     root.SubElement('d')

     print ET.tostring(root)

 Stefan

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Re: Language mavens: Is there a programming with if then else ENDIF syntax?

On the topic of switch statements and even-more-concise-then-we-have-
already if/elif/else/end constructs, I have to say that Python does
occasionally force you to write code like the code below.  Maybe
force is too strong a word, but Python lends itself to if/elif
blocks like below, which get the job done just fine, but which are not
syntactically pretty, due to the (el){0,1}if kind == duplication.
There are often cases where if/elif statements are just a smell that
you do not know how to do dictionary lookups, but if you converted the
below code to use dictionary lookups, you would complicate the code
almost as much as you abstracted the code, if not more, unless I am
just being very naive.  Anonymous methods would help to a certain
degree.  I am not saying I want either anonymous methods or switch
statements, but the lack of either in a language leads to very
procedural looking code when you use number-of-lines-of-code as a
(possibly dubious) metric.

Maybe this excerpt can be golfed down to something simpler, I would
love to see it!

if kind == 'dict':
return dictionary_schema(ast)
elif kind == 'list':
method = dictionary_schema(ast)
return lambda lst: map(method, lst)
elif kind == 'attr':
return ((lambda obj: getattr(obj, ast.field)), ast.field)
elif kind == 'key':
return (lambda obj: obj.get(ast.field), ast.field)
elif kind == 'as':
method, old_name = schema(ast.parent)
return (method, ast.synonym)
elif kind == 'call':
method, old_name = schema(ast.parent)
def call(obj):
return method(obj)()
return (call, old_name)
elif kind == 'recurse':
expr = ast.expr
kind = expr.kind
method, field_name = schema(ast.parent)
if kind in ['attr', 'key']:
new_method, new_field_name = schema(expr)
field_name = new_field_name
elif kind in ['dict', 'list']:
new_method = schema(expr)
else:
raise Exception('unknown kind!')
def recurse(obj):
obj = method(obj)
return new_method(obj)
return (recurse, field_name)
else:
raise Exception('unknown kind!')
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Re: What is the difference between 'except IOError as e:' and 'except IOError, e:'

2009-11-18 Thread Marcus Gnaß

See also
http://docs.python.org/dev/3.0/whatsnew/2.6.html#pep-3110-exception-handling-changes
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Re: Language mavens: Is there a programming with if then else ENDIF syntax?

On Wed, Nov 18, 2009 at 1:15 AM, Steve Howell showel...@yahoo.com wrote:
 On the topic of switch statements and even-more-concise-then-we-have-
 already if/elif/else/end constructs, I have to say that Python does
 occasionally force you to write code like the code below.  Maybe
 force is too strong a word, but Python lends itself to if/elif
 blocks like below, which get the job done just fine, but which are not
 syntactically pretty, due to the (el){0,1}if kind == duplication.
 There are often cases where if/elif statements are just a smell that
 you do not know how to do dictionary lookups, but if you converted the
 below code to use dictionary lookups, you would complicate the code
 almost as much as you abstracted the code, if not more, unless I am
 just being very naive.

I'm gonna have to disagree and say using the dictionary dispatch
technique would clean it up a good bit.
Yes, it would entail creating several functions, but those functions
could then be documented (vs. the currently opaque code blocks); and
due to their separation and smaller length, they would be easier to
understand and test than the given code.
Additionally, the sheer length of the given code segment probably
constitutes a code smell in and of itself for the function containing
that code.

Cheers,
Chris
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pygtk - icons?

2009-11-18 Thread Helmut Jarausch


Hi,

please bear in mind that I'm an absolute newcomer to (py)gtk.
I'm trying to install the nice synchronization tool
http://live.gnome.org/Conduit

which is written in Python and use pyGTK.

This installed several icons e.g.
/usr/share/icons/hicolor/16x16/apps/conduit.png

When run, Conduit fails to find its icons.

For testing purposes I've tried

import gtk
info=gtk.icon_theme_get_default().lookup_icon(conduit,16,0)

which produces the error message
 GtkWarning: Could not find the icon 'conduit'. The 'hicolor' theme
was not found either, perhaps you need to install it.
You can get a copy from:
http://icon-theme.freedesktop.org/releases



On my Gentoo system lots of packages have placed icons under
/usr/share/icons/hicolor

So, what am I missing.

Many thanks for a hint,
Helmut.

--
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Lehrstuhl fuer Numerische Mathematik
RWTH - Aachen University
D 52056 Aachen, Germany
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Re: Language mavens: Is there a programming with if then else ENDIF syntax?

On Nov 18, 1:32 am, Chris Rebert c...@rebertia.com wrote:
 On Wed, Nov 18, 2009 at 1:15 AM, Steve Howell showel...@yahoo.com wrote:
  On the topic of switch statements and even-more-concise-then-we-have-
  already if/elif/else/end constructs, I have to say that Python does
  occasionally force you to write code like the code below.  Maybe
  force is too strong a word, but Python lends itself to if/elif
  blocks like below, which get the job done just fine, but which are not
  syntactically pretty, due to the (el){0,1}if kind == duplication.
  There are often cases where if/elif statements are just a smell that
  you do not know how to do dictionary lookups, but if you converted the
  below code to use dictionary lookups, you would complicate the code
  almost as much as you abstracted the code, if not more, unless I am
  just being very naive.

 I'm gonna have to disagree and say using the dictionary dispatch
 technique would clean it up a good bit.
 Yes, it would entail creating several functions, but those functions
 could then be documented (vs. the currently opaque code blocks); and
 due to their separation and smaller length, they would be easier to
 understand and test than the given code.
 Additionally, the sheer length of the given code segment probably
 constitutes a code smell in and of itself for the function containing
 that code.


If you introduce seven tiny little methods, aren't you increasing the
length of the module by seven lines and introducing more complexity
with the dispatch mechanism? (Actually, it's 14 lines more if you put
a line of whitespace between your methods, and then you are also
blurring an important cue that each of the seven code blocks all
perform within the same context.)

I do agree with your point that separate methods lead to easier unit
testing.

I'm a little more skeptical about the documentation/understanding
argument, since code is often best understood within the context of
surrounding code.  I am also a bit skeptical of any coding technique
that leads to lexical duplication like {'attr': process_attr, 'key':
process_key, 'call': process_call}(ast); that is just replacing one
smell with another.  Of course, you could do something like __modules__
[kind](ast) too, but that gets a bit overly abstract for a simple
dispatch.

Having said all that, I'm gonna take your suggestion...thanks for the
response!


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Re: A different take on finding primes

2009-11-18 Thread Anh Hai Trinh

 1) google list of prime numbers
 2) see Prime numbers list in the results (number 3 in the results)
 3) click link that leads towww.prime-numbers.org

 I found 455042511 prime numbers in approx 15 seconds.

Not bad at all. How about using http://www.sagemath.org/ (written in
Python).

sage: time primes_first_n(10^7);
CPU times: user 4.36 s, sys: 2.43 s, total: 6.79 s
Wall time: 6.88 s

That used 3G of RAM, you could certainly go higher if you have more
memory.

aht
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Re: TODO and FIXME tags

2009-11-18 Thread Jean-Michel Pichavant


Scott David Daniels wrote:

Martin P. Hellwig wrote:

Ben Finney wrote:

Chris Rebert c...@rebertia.com writes:


2009/11/16 Yasser Almeida Hernández pedro...@fenhi.uh.cu:

How is the sintaxis for set the TODO and FIXME tags...?

...

There's no widely-followed “syntax” for this convention, though.
Except for _not_ doing what is suggested in those comments, which 
appears to be the biggest convention :-)


Perhaps: The comments are a directive to delete the comment if
you happen do this.

--Scott David Daniels
scott.dani...@acm.org
I guess the world is split in two categories, those how come back to fix 
the TODO, and those how don't. I for myself belong to the second, that 
is why I never write TODO comments, I either do the stuff or consider 
this is not important enough to waste time on it. In other words I 
mostly agree with Martin, and envy people belonging to the first category.


JM
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Re: Language mavens: Is there a programming with if then else ENDIF syntax?

On Nov 18, 1:32 am, Chris Rebert c...@rebertia.com wrote:
 On Wed, Nov 18, 2009 at 1:15 AM, Steve Howell showel...@yahoo.com wrote:
  On the topic of switch statements and even-more-concise-then-we-have-
  already if/elif/else/end constructs, I have to say that Python does
  occasionally force you to write code like the code below.  Maybe
  force is too strong a word, but Python lends itself to if/elif
  blocks like below, which get the job done just fine, but which are not
  syntactically pretty, due to the (el){0,1}if kind == duplication.
  There are often cases where if/elif statements are just a smell that
  you do not know how to do dictionary lookups, but if you converted the
  below code to use dictionary lookups, you would complicate the code
  almost as much as you abstracted the code, if not more, unless I am
  just being very naive.

 I'm gonna have to disagree and say using the dictionary dispatch
 technique would clean it up a good bit.
 Yes, it would entail creating several functions, but those functions
 could then be documented (vs. the currently opaque code blocks); and
 due to their separation and smaller length, they would be easier to
 understand and test than the given code.
 Additionally, the sheer length of the given code segment probably
 constitutes a code smell in and of itself for the function containing
 that code.



Here's the rewrite.  The indirection from the definition of _dict to
the first use of _dict is a little painful (36 lines away), but apart
from that I am pleased with how the new code looks, so your points are
well taken:

kind = ast.kind
def _dict(ast):
return dictionary(ast, metavar)

def _list(ast):
ignore, code = dictionary(ast, 'item')
code = '[%s for item in %s]' % (code, metavar)
return label, code

def _attr(ast):
return ast.field, '%s.%s' % (metavar, ast.field)

def _key(ast):
return ast.field, '%s[%s]' % (metavar, repr(ast.field))

def _as(ast):
ignore, parent = _code_generate(ast.parent, metavar)
return ast.synonym, parent

def _call(ast):
parent_name, parent = _code_generate(ast.parent, metavar)
parent += '()'
return parent_name, parent

def _recurse(ast):
parent = ast.parent
expr = ast.expr
parent_name, parent = _code_generate(parent, metavar)
kind = expr.kind
if kind in ['attr', 'key', 'list']:
parent_name, parent = _code_generate(expr, parent,
parent_name)
else:
subparent_name, subparent = _code_generate(expr,
parent_name)
parent = '(lambda %s:\n' % parent_name + indent_block
(subparent+')(%s)' % parent)
return parent_name, parent

dispatches = {
'dict': _dict,
'list': _list,
'attr': _attr,
'key': _key,
'as': _as,
'call': _call,
'recurse': _recurse,
}
if kind in dispatches:
return dispatches[kind](ast)
else:
raise Exception('unknown kind!')

Thanks!

P.S. The underscores before the method names might look a little funny
for inner methods, but it's the nature of the code..._dict and _list
would lead to confusion with builtins, if not actual conflict.
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Re: Stagnant Frame Data?

2009-11-18 Thread Mike

On Nov 15, 1:36 pm, Terry Reedy tjre...@udel.edu wrote:
 Peter Otten wrote:
  Mike wrote:

  I'll apologize first for this somewhat lengthy example. It does
  however recreate the problem I've run into. This is stripped-down code
  from a much more meaningful system.

  I have two example classes, AutoChecker and Snapshot that evaluate
  variables in their caller's namespace using the frame stack. As
  written, the output is not what is expected: the variables evaluate to
  stagnant values.

  However, if the one indicated line is uncommented, then the result is
  as expected.

  So my questions are: Is this a bug in Python?

 No. The existence and use of sys._getframe -- notice the leading
 underscore -- is a CPython implementation artifact. Use at your own risk.

   Is this an invalid use of frame data?

 Up to you to decide.

   Why does the single line sys._getframe(1).f_locals

  fix the behavior?

 It updates the dictionary.



  A simplified demonstration of your problem:

  def f(update):
  ...     a = locals()
  ...     x = 42
  ...     if update: locals()
  ...     print a
  ...
  f(False)
  {'update': False}
  f(True)
  {'a': {...}, 'x': 42, 'update': True}

  The local namespace is not a dictionary, and the locals()/f_locals
  dictionary contains a snapshot of the local namespace. Accessing the
  f_locals attribute is one way to trigger an update of that snapshot.

  What's puzzling is that the same dictionary is reused.

 Efficiency? Consistency? The doc for locals says locals()
 Update and return a dictionary representing the current local symbol
 table. In class statements, where (currently) the local namespace *is*
 a dict, no update is needed and locals() simply returns the dict, the
 same one each time.

 Terry Jan Reedy

Thanks for the replies.

If Peter's concise and much-appreciated example were to be modified as
such:

 def f(update):
   .: a = inspect.stack()[0][0].f_locals
   .: x = 42
   .: if update:
   .: inspect.stack()[0][0].f_locals
   .: print a
   .:
 f(False)
{'update': False}
 f(True)
{'a': {...}, 'x': 42, 'update': True}

Now there's no use of locals() to perform its documented Update, but
just a simple access of a dictionary. This behavior is curious.

Further modification by accessing 'a' instead of '...f_locals' upon
update produces:

 f(False)
{'update': False}
 f(True)
{'update': True}

Checking the id() of 'a' and '...f_locals' shows the same address.

How is it that '...f_locals' gets updated in this example? Is it done
in stack()?

Where exactly is the frame data stored prior to updating the
dictionary and can I get to it?

Thanks,
Mike
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Re: Stagnant Frame Data?

2009-11-18 Thread Mike

On Nov 15, 1:36 pm, Terry Reedy tjre...@udel.edu wrote:
 Peter Otten wrote:
  Mike wrote:

  I'll apologize first for this somewhat lengthy example. It does
  however recreate the problem I've run into. This is stripped-down code
  from a much more meaningful system.

  I have two example classes, AutoChecker and Snapshot that evaluate
  variables in their caller's namespace using the frame stack. As
  written, the output is not what is expected: the variables evaluate to
  stagnant values.

  However, if the one indicated line is uncommented, then the result is
  as expected.

  So my questions are: Is this a bug in Python?

 No. The existence and use of sys._getframe -- notice the leading
 underscore -- is a CPython implementation artifact. Use at your own risk.

   Is this an invalid use of frame data?

 Up to you to decide.

   Why does the single line sys._getframe(1).f_locals

  fix the behavior?

 It updates the dictionary.



  A simplified demonstration of your problem:

  def f(update):
  ...     a = locals()
  ...     x = 42
  ...     if update: locals()
  ...     print a
  ...
  f(False)
  {'update': False}
  f(True)
  {'a': {...}, 'x': 42, 'update': True}

  The local namespace is not a dictionary, and the locals()/f_locals
  dictionary contains a snapshot of the local namespace. Accessing the
  f_locals attribute is one way to trigger an update of that snapshot.

  What's puzzling is that the same dictionary is reused.

 Efficiency? Consistency? The doc for locals says locals()
 Update and return a dictionary representing the current local symbol
 table. In class statements, where (currently) the local namespace *is*
 a dict, no update is needed and locals() simply returns the dict, the
 same one each time.

 Terry Jan Reedy

Thanks for the replies.

If Peter's concise and much-appreciated example were to be modified as
such:

 def f(update):
   .: a = inspect.stack()[0][0].f_locals
   .: x = 42
   .: if update:
   .: inspect.stack()[0][0].f_locals
   .: print a
   .:
 f(False)
{'update': False}
 f(True)
{'a': {...}, 'x': 42, 'update': True}

Now there's no use of locals() to perform its documented Update, but
just a simple access of a dictionary. This behavior is curious.

Further modification by accessing 'a' instead of '...f_locals' upon
update produces:

 f(False)
{'update': False}
 f(True)
{'update': True}

Checking the id() of 'a' and '...f_locals' shows the same address.

How is it that '...f_locals' gets updated in this example? Is it done
in stack()?

Where exactly is the frame data stored prior to updating the
dictionary and can I get to it?

Thanks,
Mike
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PyQt4 4.4.4 : a bug with highlightBlock ?

2009-11-18 Thread Snouffy

Hello everybody,

I've been trying to do some syntax highlighting using PyQt4. I ported
the example given in the documentation of Qt4 to Python. It works fine
on my computer at work (which has PyQt4 version 4.3.3) but doesn't on
my home computer (which has version 4.4.4) : it gets stuck in an
infinite loop.
Here is the code :

class MyHighlighter(QtGui.QSyntaxHighlighter):
def __init__(self, edit):
QtGui.QSyntaxHighlighter.__init__(self,edit)

def highlightBlock(self, text):
myClassFormat = QtGui.QTextCharFormat()
myClassFormat.setFontWeight(QtGui.QFont.Bold)
myClassFormat.setForeground(QtCore.Qt.darkMagenta)
pattern = \\b[A-Z_]+\\b

expression = QtCore.QRegExp(pattern)
index = text.indexOf(expression);
while (index = 0):
length = expression.matchedLength()
self.setFormat(index, length, myClassFormat)
index = text.indexOf(expression, index + length)


What am I missing ? Is this a known bug of version 4.4.4 ?

Thank you,

Alexis.
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getting properly one subprocess output

2009-11-18 Thread Jean-Michel Pichavant


Hi python fellows,

I'm currently inspecting my Linux process list, trying to parse it in 
order to get one particular process (and kill it).

I ran into an annoying issue:
The stdout display is somehow truncated (maybe a terminal length issue, 
I don't know), breaking my parsing.


import subprocess
commandLine = ['ps', '-eo %p %U %P %y %t %C %c %a']
process = subprocess.Popen(commandLine, stdout=subprocess.PIPE, 
stderr=subprocess.PIPE)

processList, stderrdata = process.communicate()

Here is a sample of what I get in processList.split('\n'):

' 25487 1122  4344 ? 7-17:48:32  2.5 firefox-bin 
/usr/lib/iceweasel/firefox-',
' 25492 1122  4892 pts/6  00:08 57.2 ipython 
/usr/bin/python /usr/bin/ip',



As you can see, to complete process command line is truncated.
Any clue on how to get the full version ?

JM

(python 2.5)
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Re: ANN: Urwid 0.9.9 - Console UI Library

2009-11-18 Thread Daniel Fetchinson

 How did you make the html 'screenshots'? I guess you have some kind of
 urwid2html tool or some such or is it plain ncurses?

 It's all handled in the demo code. This is from tour.py:

 if urwid.web_display.is_web_request():
 screen = urwid.web_display.Screen()
 else:
 screen = urwid.raw_display.Screen()

Thanks, I missed that.

 Urwid is really cool!

 No argument there :)

None, indeed.

Cheers,
Daniel




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Re: Accessing a Web server --- how?

2009-11-18 Thread Nick Stinemates

This is what the History and Compare URL translates to:

http://service.nordea.com/nordea-openpages/six.action?target=/nordea.public/bond/nordeabond.pagemagic=(cc+(detail+(tsid+310746)+(view+hist)))

Some questions..
Do you have an idea on what the tsid is? It looks like it's a unique
identifier for the chart and the only thing you'll need to change.

Are you only interested in this chart or others?

How would you like to extract the data? Is saving the chart enough or would you
like to extract values from the chart?

On Mon, Nov 16, 2009 at 11:14:26AM +0100, Virgil Stokes wrote:
If one goes to the following URL:
http://www.nordea.se/Privat/Spara%2boch%2bplacera/Strukturerade%2bprodukter/Aktieobligation%2bNr%2b99%2bEuropa%2bAlfa/973822.html

it contains a link (click on Current courses NBD AT99 3113A) to:
http://service.nordea.com/nordea-openpages/six.action?target=/nordea.public/bond/nordeabond.pagemagic=%28cc+%28detail+%28tsid+310746%29%29%29;

and if you now click on the tab labeled history and compare this will
take you to:
http://service.nordea.com/nordea-openpages/six.action?target=/nordea.public/bond/nordeabond.pagemagic=%28cc+%28detail+%28tsid+310746%29+%28view+hist%29%29%29;

Finally...This is where I would like to connect to the data on a daily
basis or to gather data over different time intervals. I believe that if
I can get some help on this, then I will be able to customize the code
as needed for my own purposes.

It should be clear that this is financial data on a fond managed by
Nordea Bank AB. Nordea is one of the largest banks in Scandinavia.

Note, that I do have some experience with Python (2.6 mainly), and find
it a very useful and powerful language. However, I have no experience
with it in the area of Web services. Any suggestions/comments on how to
set up this financial data service project would be greatly appreciated,
and I would be glad to share this project with any interested parties.

Note, I posted a similar message to the list pywebsvcs; but, received no
responses.

-- V. Stokes

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Re: A different take on finding primes

2009-11-18 Thread Nigel Rowe

On Tue, 17 Nov 2009 05:21, Tobiah wrote in comp.lang.python
okgmm.17283$et3.3...@newsfe17.iad:

 
 Let me
 be clear, given 2min, how many primes can you find, they need not be
in
 order or consecutive.
 
 Do they have to go from low to high?   :( )

1) google list of prime numbers
2) see Prime numbers list in the results (number 3 in the results) 
3) click link that leads to www.prime-numbers.org

I found 455042511 prime numbers in approx 15 seconds.

Is that what you wanted?

-- 
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rho (snail) fisheggs (stop) name
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Re: Language mavens: Is there a programming with if then else ENDIFsyntax?

2009-11-18 Thread bartc


Dotan Cohen wrote:

2009/11/16 Steve Ferg steve.ferg.bitbuc...@gmail.com:



I've often thought that a language with this kind of block-free
syntax would be nice and intuitive:

if condition then
do stuff
elif condition then
do stuff
else
do stuff
endif

Note that you do not need block delimiters.



Does anybody know a language with this kind of syntax for
ifThenElseEndif?



PHP has exactly this:

if (condition) {
   // stuff
} elseif (otherContition) {
  // otherStuff
} elseif (yetAnotherCondition) {
  // yetOtherStuff
}


The OP explicitly said no block delimiters. Your example uses {..}, and 
doesn't have endif.


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Re: python simply not scaleable enough for google?

2009-11-18 Thread sturlamolden

On 18 Nov, 00:31, Terry Reedy tjre...@udel.edu wrote:

 The
 problem for the future is the switch to multiple cores for further speedups.

The GIL is not a big problem for scientists. Scientists are not so
dependent on threads as the Java/webdeveloper crowd:

- We are used to running multiple processes with MPI.

- Numerical libraries running C/Fortran/Assembler will often release
the GIL. Python threads are ok for multicores then.

- Numerical libraries can be written or compiles for multicores e.g.
using OpenMP or special compilers. If FFTW is compiled for multiple
cores it does not matter that Python has a GIL. LAPACK will use
multiple cores if you use MKL or GotoBLAS, regardless of the GIL.
Etc.

- A scientist used to MATLAB will think MEX function (i.e. C or
Fortran) if something is too slow. A web developer used to Java will
think multithreading.
































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Re: python simply not scaleable enough for google?

2009-11-18 Thread sturlamolden

On 18 Nov, 00:24, greg g...@cosc.canterbury.ac.nz wrote:

 NumPy, for example, is *extremely* flexible. Someone put
 in the effort, once, to write it and make it fast -- and
 now an endless variety of programs can be written very easily
 in Python to make use of it.

I'm quite sure David Cournapeau knows about NumPy...

By the way, NumPy is not particularly fast because of the way it is
written. It's performance is hampered by the creation of temporary
arrays. But NumPy provides a flexible way of managing memory in
scientific programs.






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break LABEL vs. exceptions + PROPOSAL

2009-11-18 Thread Lo'oris

I've found this email, back from 10 years ago:
http://mail.python.org/pipermail/python-list/1999-September/009983.html

I guess it went unnoticed, because that proposal looks really
intresting.

• break labels have been refused into python
• we can do it anyway using exceptions
• this is a proposal for something better, resembling the exception
way and much more powerful and python-like than break labels
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Re: Language mavens: Is there a programming with if then else ENDIF syntax?

2009-11-18 Thread Simon Brunning

2009/11/17 sjm sjms...@gmail.com:
 On Nov 16, 12:54 pm, Steve Ferg steve.ferg.bitbuc...@gmail.com
 wrote:
 snip
 Does anybody know a language with this kind of syntax for
 ifThenElseEndif?

 Modern-day COBOL:

 IF      some-condition
        do-something
 ELSE
        do-something-else
 END-IF.

RPG/400's SELEC statement: http://bit.ly/2LDegk

Thing of beauty.

Cheers,
Simon B.
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Re: break LABEL vs. exceptions + PROPOSAL

On Wed, Nov 18, 2009 at 4:05 AM, Lo'oris loo...@gmail.com wrote:
 I've found this email, back from 10 years ago:
 http://mail.python.org/pipermail/python-list/1999-September/009983.html

 I guess it went unnoticed, because that proposal looks really
 intresting.

 • break labels have been refused into python
 • we can do it anyway using exceptions
 • this is a proposal for something better, resembling the exception
 way and much more powerful and python-like than break labels

You're gonna have to wait 18-24 months:
http://www.python.org/dev/peps/pep-3003/

Also, the python-ideas list might be a better forum for discussing
this than the general-interest list:
http://mail.python.org/mailman/listinfo/python-ideas

Cheers,
Chris
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Re: ANN: a mini-language for encapsulating deep-copy operations on Python data structures

2009-11-18 Thread M.-A. Lemburg

Steve Howell wrote:
 During the last few days I have written code in support of a small DDL
 language that encapsulates a concise representation of the
 manipulations needed to make a deep subcopy of a Python-like data
 structure. It is inspired by syntax from mainstream modern languages,
 including, of course, Python. The DDL can be converted to an AST. That
 AST can be walked to either generate Python code that expresses the
 mapping or to generate Python objects that can execute the mapping.
 Either of the prior outputs can then subsequently be applied to real
 world inputs to create new Python data structures from old ones, using
 the mechanisms specified in the original DDL for attribute access,
 dictionary lookup, iteration, method invocation, etc.
 
 Here is an example of the DDL (and I hate the terminology DDL, just
 cannot think of anything better):
 
 
 {
 'show_table_of_contents',
 'author' {
 .person 'name',
 .person 'location' as city,
 .favorite_books()[
 .title,
 .cost() as expense
 ] as books}
 }
 

 There are more details here:
 
 http://showellonprogramming.blogspot.com/2009/11/more-on-python-deep-copy-schema.html

Personally, I find the explicit approach more intuitive, since
you immediately see what you are going to get:

show_table_of_contents = context['show_table_of_contents']
author = context['author']
d = {
'show_table_of_contents': show_table_of_contents,
'author': {
'name': author.person['name'],
'city': author.person['location'],
'books': [{
'title': item.title,
'expense': item.cost(),
}
for item in author.favorite_books()],
},
}

I particularly find this part non-intuitive:

 .favorite_books()[
 .title,
 .cost() as expense
 ] as books}

and would leave in the square brackets for __getitem__
lookups on these:

 .person 'name',
 .person 'location' as city,

For additional inspiration, you might want to look at XSLT
which provides similar transformations on XML data structures.

There are also a number of other transformation languages:

http://en.wikipedia.org/wiki/Model_Transformation_Language
http://en.wikipedia.org/wiki/Data_transformation

Regarding the term DDL: that's normally used for data definition
language and doesn't really have all that much to do with
transforming data. You normally define data structures using
DDL - without actually putting data into those structures.

Why not PyDTL Python data transformation language ?!

-- 
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eGenix.com

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Minimally intrusive XML editing using Python

2009-11-18 Thread Thomas Lotze

I wonder what Python XML library is best for writing a program that makes
small modifications to an XML file in a minimally intrusive way. By that I
mean that information the program doesn't recognize is kept, as are
comments and whitespace, the order of attributes and even whitespace
around attributes. In short, I want to be able to change an XML file while
producing minimal textual diffs.

Most libraries don't allow controlling the order of and the whitespace
around attributes, so what's generally left to do is store snippets of
original text along with the model objects and re-use that for writing the
edited XML if the model wasn't modified by the program. Does a library
exist that helps with this? Does any XML library at all allow structured
access to the text representation of a tag with its attributes?

Thank you very much.

-- 
Thomas


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Re: Redirect stdout to a buffer [Errno 9]

2009-11-18 Thread Ecir Hana

On Nov 17, 6:51 am, Gabriel Genellina gagsl-...@yahoo.com.ar
wrote:

 The code below now reads from the pipe everything that has been written --  
 except from Python :(

Thanks a lot for the fine code! So far I don't know why it fails to
print from Python - I'll post here any news I get...

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Re: Minimally intrusive XML editing using Python

2009-11-18 Thread Stefan Behnel

Thomas Lotze, 18.11.2009 13:55:
 I wonder what Python XML library is best for writing a program that makes
 small modifications to an XML file in a minimally intrusive way. By that I
 mean that information the program doesn't recognize is kept, as are
 comments and whitespace, the order of attributes and even whitespace
 around attributes. In short, I want to be able to change an XML file while
 producing minimal textual diffs.

Take a look at canonical XML (C14N). In short, that's the only way to get a
predictable XML serialisation that can be used for textual diffs. It's
supported by lxml.

Stefan
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Re: Minimally intrusive XML editing using Python

On Wed, Nov 18, 2009 at 4:55 AM, Thomas Lotze tho...@thomas-lotze.de wrote:
 I wonder what Python XML library is best for writing a program that makes
 small modifications to an XML file in a minimally intrusive way. By that I
 mean that information the program doesn't recognize is kept, as are
 comments and whitespace, the order of attributes and even whitespace
 around attributes. In short, I want to be able to change an XML file while
 producing minimal textual diffs.

 Most libraries don't allow controlling the order of and the whitespace
 around attributes, so what's generally left to do is store snippets of
 original text along with the model objects and re-use that for writing the
 edited XML if the model wasn't modified by the program. Does a library
 exist that helps with this? Does any XML library at all allow structured
 access to the text representation of a tag with its attributes?

Have you considered using an XML-specific diff tool such as:
* One off this list:
http://www.manageability.org/blog/stuff/open-source-xml-diff-in-java
* xmldiff (it's in Python even): http://www.logilab.org/859
* diffxml: http://diffxml.sourceforge.net/

[Note: I haven't actually used any of these.]

Cheers,
Chris
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Re: Minimally intrusive XML editing using Python

2009-11-18 Thread Thomas Lotze

Stefan Behnel wrote:

 Take a look at canonical XML (C14N). In short, that's the only way to get a
 predictable XML serialisation that can be used for textual diffs. It's
 supported by lxml.

Thank you for the pointer. IIUC, c14n is about changing an XML document so
that its textual representation is reproducible. While this representation
would certainly solve my problem if I were to deal with input that's
already in c14n form, it doesn't help me handling arbitrarily formatted
XML in a minimally intrusive way.

IOW, I don't want the XML document to obey the rules of a process, but
instead I want a process that respects the textual form my input happens
to have.

-- 
Thomas


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Re: Minimally intrusive XML editing using Python

2009-11-18 Thread Thomas Lotze

Chris Rebert wrote:

 Have you considered using an XML-specific diff tool such as:

I'm afraid I'll have to fall back to using such a thing if I don't find a
solution to what I actually want to do.

I do realize that XML isn't primarily about its textual representation, so
I guess I shouldn't be surprised if what I'm looking for doesn't exist.
Still, it would be nice if it did...

-- 
Thomas


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Re: ast manipulation

2009-11-18 Thread Tsize

Terry,

Thank you for responding.  I actually figured out how to do this
shortly after posting the message.  Sorry I wasn't quite clear enough
in my post, I will try to be a little more explict in the future.
Just to mention it I want to go to each node in the ast including
child nodes and change the values.  I am making a limited mutation
analysis program. If it looks generally useful as I get further along
I will release the code.  I did an early prototype that worked on the
text of the code itself but I thought that using the ast for this
would be better and maybe a little faster.

Regards,
Thomas

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Inserting Unicode text with MySQLdb in Python 2.4-2.5?

2009-11-18 Thread Keith Hughitt

Hi all,

I ran into a problem recently when trying to add support for earlier
versions of Python (2.4 and 2.5) to some database related code which
uses MySQLdb, and was wondering if anyone has any suggestions.

With later versions of Python (2.6), inserting Unicode is very simple,
e.g.:

# -*- coding: utf-8 -*-
...
cursor.execute('''INSERT INTO `table` VALUES (0,
'Ångström'),...''')

When the same code is run on earlier versions, however, the results is
either garbled text (e.g. Ã or ? instead of Å in Python 2.5), or
an exception being thrown (Python 2.4):

UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in
position 60: ordinal not in range(128)

So far I've tried a number of different things, including:

1. Using Unicode strings (e.g. u\u212B)

2. Manually specifying the encoding using sys.setdefaultencoding
('utf-8')

3. Manually enabling Unicode support in MySQLdb
(use_unicode=False, charset = utf8)

...but no combination of any of the above resulted in proper database
content.

To be certain that the issue was related to Python/MySQLdb and not
MySQL itself, I manually inserted the text and it worked just fine.
Furthermore, when working in a Python console, both print Å and
print u\u212B display the correct output.

Any ideas? The versions of the MySQLdb adapter tested were 1.2.1
(Python 2.4), and 1.2.2-10 (Python 2.5).

Thanks!
Keith
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Re: Inserting Unicode text with MySQLdb in Python 2.4-2.5?

2009-11-18 Thread Diez B. Roggisch

Keith Hughitt wrote:

 Hi all,
 
 I ran into a problem recently when trying to add support for earlier
 versions of Python (2.4 and 2.5) to some database related code which
 uses MySQLdb, and was wondering if anyone has any suggestions.
 
 With later versions of Python (2.6), inserting Unicode is very simple,
 e.g.:
 
 # -*- coding: utf-8 -*-
 ...
 cursor.execute('''INSERT INTO `table` VALUES (0,
 'Ångström'),...''')

You are aware that the coding-declaration only affects unicode-literals (the
ones like ui'm unicode)? So the above insert-statement is *not* unicode,
it's a byte-string in whatever encoding your editor happens to save the
file in.

And that's point two: make sure your editor reads and writes the file in the
same encoding you specified in the comment in the beginning. 

 
 When the same code is run on earlier versions, however, the results is
 either garbled text (e.g. Ã or ? instead of Å in Python 2.5), or
 an exception being thrown (Python 2.4):
 
 UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in
 position 60: ordinal not in range(128)

Makes sense if the execute tries to encode to unicode first - as you didn't
give it a unicode-object.

 
 So far I've tried a number of different things, including:
 
 1. Using Unicode strings (e.g. u\u212B)
 
 2. Manually specifying the encoding using sys.setdefaultencoding
 ('utf-8')
 
 3. Manually enabling Unicode support in MySQLdb
 (use_unicode=False, charset = utf8)

You *disabled* unicode here! Unicode is NOT utf-8!!! 

http://www.joelonsoftware.com/articles/Unicode.html


 
 ...but no combination of any of the above resulted in proper database
 content.
 
 To be certain that the issue was related to Python/MySQLdb and not
 MySQL itself, I manually inserted the text and it worked just fine.
 Furthermore, when working in a Python console, both print Å and
 print u\u212B display the correct output.
 
 Any ideas? The versions of the MySQLdb adapter tested were 1.2.1
 (Python 2.4), and 1.2.2-10 (Python 2.5).

Try the above, and better yet provide self-contained examples that show the
behavior.

Diez
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base64MIME problem, Or Just New Email Client

2009-11-18 Thread Victor Subervi

Hi;
I'm using SimpleMail, available from SF, that used to work fine for me but
now I can't build it on my new server. I get this error:

[Tue Nov 17 09:53:13 2009] [error] [client 208.84.198.58] import
smtplib, referer:
http://globalsolutionsgroup.vi/display_spreadsheet.py
[Tue Nov 17 09:53:13 2009] [error] [client 208.84.198.58]   File
/usr/lib64/python2.4/smtplib.
py, line 49, in ?, referer:
http://globalsolutionsgroup.vi/display_spreadsheet.py
[Tue Nov 17 09:53:13 2009] [error] [client 208.84.198.58] from
email.base64MIME import encode as encode_base64, referer:
http://globalsolutionsgroup.vi/display_spreadsheet.py
[Tue Nov 17 09:53:13 2009] [error] [client 208.84.198.58] ImportError:
No module named base64MIME, referer:
http://globalsolutionsgroup.vi/display_spreadsheet.py
[Tue Nov 17 09:53:13 2009] [error] [client 208.84.198.58] Premature
end of script headers: mail.py, referer:
http://globalsolutionsgroup.vi/display_spreadsheet.py

So, let's try this:
[r...@13gems simplemail]# find . |xargs grep 'base64MIME'
[r...@13gems simplemail]#

What gives? Well, if there ain't no solving this one, can someone recommend
a good client for easily generating emails from forms to inject into qmail?
TIA,
Victor
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Re: open source linux - windows database connectivity?

2009-11-18 Thread Tony Schmidt

Woo-hoo!  Forget ODBC.  Got this working with Jython and JDBC drivers!

On Nov 13, 1:03 am, M.-A. Lemburg m...@egenix.com wrote:
 TonySchmidtwrote:
  Note: The client part of this product is free. You only need to
  get a license for the server part.

  Yeah, but don't I need the server part to make the connection?

 Sure, but you don't need to get a license per client, unlike for
 e.g. the combination mxODBC + EasySoft OOB.

 Regards,
 --
 Marc-Andre Lemburg
 eGenix.com

 Professional Python Services directly from the Source  (#1, Nov 13 2009) 
 Python/Zope Consulting and Support ...        http://www.egenix.com/
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 ::: Try our new mxODBC.Connect Python Database Interface for free ! 

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best performance for storage of server information for python CGI web app?

2009-11-18 Thread davidj411

I am wondering what will give me the best performance for storing
information about the servers in our environment.
currently i store all info about all servers in a single shelve file,
but i have concerns.
1) as the size of the shelve file increases, will performance suffer ?
2) what about if 2 updates occur at the same time to the shelve file?
when a shelve file is opened, is the whole file read into memory?

if either scenario (1 or 2) is true, then should i think about
creating a shelve file per server?
i was also thinking about using SQL Lite with one DB to store all the
info.
with this option, i would not have to worry about concurrent updates,
but as the file size increases, i could expect performance to suffer
again?

I am running Python 2.6 CGI scripts on Apache web server on windows
platform. they interact with the current shelve file to pull info or
request info from a python service which will go collect the info and
put it into the shelve file.
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Re: IOError: [Errno 28] No space left on device

2009-11-18 Thread Grant Edwards

On 2009-11-18, hong zhang henryzhan...@yahoo.com wrote:

 Apparently the harddisk where you stored the file is full?

It's not a real file, and takes up no space.

 I have plenty space see:
 $ df -l
 Filesystem   1K-blocks  Used Available Use% Mounted on
 /dev/sda1 74027808   4910016  65357380   7% /

That doesn't matter.  /sys doesn't contain real files.  It's an
API to access kernel internals.

 but following is good.

 cont_tx = 1
 for i in 
 glob.glob('/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx'):
  with open(i, 'w') as f:
  print f, cont_tx

Well, if that works, then what's your problem?

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  at   to tell them about my
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non-copy slices

2009-11-18 Thread tbourden

Hi,

I was looking for a facility similar to slices in python library that would
avoid the implicit creation of a new list and copy of elements that is the
default behaviour. Instead I'd rather have a lazy iteratable object on the
original sequence. Well, in the end I wrote it myself but I was wondering if
I missed sth in the library. If I didn't is there a particular reason there
isn't sth like that? I find it hard to believe that all slice needs have
strictly copy semantics.

Cheers,
Themis
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Re: non-copy slices

2009-11-18 Thread Tim Golden


tbour...@doc.ic.ac.uk wrote:

Hi,

I was looking for a facility similar to slices in python library that would
avoid the implicit creation of a new list and copy of elements that is the
default behaviour. Instead I'd rather have a lazy iteratable object on the
original sequence. Well, in the end I wrote it myself but I was wondering if
I missed sth in the library. If I didn't is there a particular reason there
isn't sth like that? I find it hard to believe that all slice needs have
strictly copy semantics.


I suspect that itertools is your friend, specifically itertools.islice

TJG
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Re: non-copy slices

2009-11-18 Thread tbourden

Ahhh yes! that's exactly it. Thanks for pointing out!

Themis


On Wed, Nov 18, 2009 at 3:44 PM, Tim Golden m...@timgolden.me.uk wrote:

 tbour...@doc.ic.ac.uk wrote:
  Hi,
 
  I was looking for a facility similar to slices in python library that
 would
  avoid the implicit creation of a new list and copy of elements that is
 the
  default behaviour. Instead I'd rather have a lazy iteratable object on
 the
  original sequence. Well, in the end I wrote it myself but I was wondering
 if
  I missed sth in the library. If I didn't is there a particular reason
 there
  isn't sth like that? I find it hard to believe that all slice needs have
  strictly copy semantics.

 I suspect that itertools is your friend, specifically itertools.islice

 TJG
 --
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Re: getting properly one subprocess output

2009-11-18 Thread Jon Clements

On Nov 18, 11:25 am, Jean-Michel Pichavant jeanmic...@sequans.com
wrote:
 Hi python fellows,

 I'm currently inspecting my Linux process list, trying to parse it in
 order to get one particular process (and kill it).
 I ran into an annoying issue:
 The stdout display is somehow truncated (maybe a terminal length issue,
 I don't know), breaking my parsing.

 import subprocess
 commandLine = ['ps', '-eo %p %U %P %y %t %C %c %a']
 process = subprocess.Popen(commandLine, stdout=subprocess.PIPE,
 stderr=subprocess.PIPE)
 processList, stderrdata = process.communicate()

 Here is a sample of what I get in processList.split('\n'):

  ' 25487 1122      4344 ?         7-17:48:32  2.5 firefox-bin    
 /usr/lib/iceweasel/firefox-',
  ' 25492 1122      4892 pts/6          00:08 57.2 ipython        
 /usr/bin/python /usr/bin/ip',

 As you can see, to complete process command line is truncated.
 Any clue on how to get the full version ?

 JM

 (python 2.5)

What about ps -eo pid,tty,cmd ?

Sample:
12680 ?geany /usr/share/gramps/ReportBase/
_CommandLineReport.py
12682 ?gnome-pty-helper
12683 pts/0/bin/bash
13038 ?gnome-terminal
13039 ?gnome-pty-helper
13040 pts/1bash
13755 pts/1ps -eo pid,tty,cmd

...etc...


hth,

Jon.



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Re: getting properly one subprocess output

2009-11-18 Thread Jon Clements

On Nov 18, 4:14 pm, Jon Clements jon...@googlemail.com wrote:
 On Nov 18, 11:25 am, Jean-Michel Pichavant jeanmic...@sequans.com
 wrote:



  Hi python fellows,

  I'm currently inspecting my Linux process list, trying to parse it in
  order to get one particular process (and kill it).
  I ran into an annoying issue:
  The stdout display is somehow truncated (maybe a terminal length issue,
  I don't know), breaking my parsing.

  import subprocess
  commandLine = ['ps', '-eo %p %U %P %y %t %C %c %a']
  process = subprocess.Popen(commandLine, stdout=subprocess.PIPE,
  stderr=subprocess.PIPE)
  processList, stderrdata = process.communicate()

  Here is a sample of what I get in processList.split('\n'):

   ' 25487 1122      4344 ?         7-17:48:32  2.5 firefox-bin    
  /usr/lib/iceweasel/firefox-',
   ' 25492 1122      4892 pts/6          00:08 57.2 ipython        
  /usr/bin/python /usr/bin/ip',

  As you can see, to complete process command line is truncated.
  Any clue on how to get the full version ?

  JM

  (python 2.5)

 What about ps -eo pid,tty,cmd ?

 Sample:
 12680 ?        geany /usr/share/gramps/ReportBase/
 _CommandLineReport.py
 12682 ?        gnome-pty-helper
 12683 pts/0    /bin/bash
 13038 ?        gnome-terminal
 13039 ?        gnome-pty-helper
 13040 pts/1    bash
 13755 pts/1    ps -eo pid,tty,cmd

 ...etc...

 hth,

 Jon.

Another thought: if you're only wanting to find and kill a process,
what about pkill? Saves you having to filter the list in Python and
then issue a kill command.

Jon.
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using struct module on a file

2009-11-18 Thread Ulrich Eckhardt

Hia!

I need to read a file containing packed binary data. For that, I find the 
struct module pretty convenient. What I always need to do is reading a chunk 
of data from the file (either using calcsize() or a struct.Struct instance) 
and then parsing it with unpack(). For that, I repeatedly write utility 
functions that help me do just that, but I can't imagine that there is no 
better way for that.

Questions:
0. Am I approaching this from the wrong direction? I'm not a programming 
noob, but rather new to Python still.
1. The struct module has pack_into() or unpack_from(), could I somehow 
combine that with a file?
2. Is there some easier way to read files? I know about array and xdrlib, 
but neither really fit my desires.
3. Failing all that, would you consider this a useful addition to the struct 
module, i.e. should I write a feature request?

Thanks!

Uli

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question about tree in python

2009-11-18 Thread nospam

How should I write a tree using diconary. I have used a dictonary to 
make a tree.


tree={best:collections.defaultdict(lambda:default)} in a id3 tree.

Is there a way to multple values and when then only return on type of 
values.


I tried this apporach but it did not work.

class Tree:
def __init__(self):
pass



def ini(self,default_tree,d_attr):
self.tree={d_attr:collections.defaultdict(lambda:default_tree)}
self.tree_A={d_attr:collections.defaultdict(lambda:default_tree)}
self.tree_I={d_attr:collections.defaultdict(lambda:default_tree)}
self.tree_p={d_attr:collections.defaultdict(lambda:default_tree)}
self.tree_n={d_attr:collections.defaultdict(lambda:default_tree)}
return self.tree

def __call__(self,best,val,subtree):
self.tree[best][val]=subtree

def 
input_tree(self,best,val,subtree,postive,negative,attribute_value,info_gain):

tree=self.tree
print best
print val
tree[best][val]=subtree
print self.tree
self.tree_A[best][val]= attribute_value
self.tree_I[best][val]= info_gain
self.tree_p[best][val]= postive
self.tree_n=negative
tree=self.tree
return tree
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Re: Beautifulsoup code that is not running

2009-11-18 Thread Peter Pearson

On Tue, 17 Nov 2009 14:38:55 -0800 (PST), Zeynel azeyn...@gmail.com wrote:
[snip]
 from BeautifulSoup import BeautifulSoup

 soup = BeautifulSoup (file(test.html).read())
 title = soup.find('title')
 titleString = title.string
 open('extract.text', 'w').write(titleString)

 This runs without an error, but nothing is written into the
 extract.text file. test.html has title/title tags in it.

Hmm.  Works for me, but of course I don't have your test.html.
Why don't you try examining title and titleString?  Perhaps
title/title has resulted in titleString being the empty string.

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Re: ANN: a mini-language for encapsulating deep-copy operations on Python data structures

On Nov 18, 4:34 am, M.-A. Lemburg m...@egenix.com wrote:
Steve Howell wrote:
[...]
Here is an example of the DDL (and I hate the terminology DDL, just
cannot think of anything better):

{
'show_table_of_contents',
'author' {
.person 'name',
.person 'location' as city,
.favorite_books()[
.title,
.cost() as expense
] as books}
}

There are more details here:

http://showellonprogramming.blogspot.com/2009/11/more-on-python-deep-...

Thanks for your feedback, Marc-Andre! Comments inline...

Personally, I find the explicit approach more intuitive, since
you immediately see what you are going to get:

show_table_of_contents = context['show_table_of_contents']
author = context['author']
d = {
'show_table_of_contents': show_table_of_contents,
'author': {
'name': author.person['name'],
'city': author.person['location'],
'books': [{
'title': item.title,
'expense': item.cost(),
}
for item in author.favorite_books()],
},
}

I understand what you mean about the explicit approach. When you go
for brevity, you sacrifice some explicitness. One of the things I'm
actually looking to do next is to be able to generate code like what
you've written above. You could make the generated code even more
procedural in terms of how it walks the structure--for example,
replace the list comprehension with a for loop. This could be useful
for inserting tracing code, for example.

I particularly find this part non-intuitive:

.favorite_books()[
.title,
.cost() as expense
] as books}

Yep, I think what I really want is this:

.favorite_books()[{
.title,
.cost() as expense
}] as books}

I am not sure the curlies make the transformation completely
intuitive, but they are more suggestive that you are generating a list
of dictionaries.

and would leave in the square brackets for __getitem__
lookups on these:

.person 'name',
.person 'location' as city,

Yep, I agree. The square brackets were not a deliberate omission.
They were just slightly more tricky to implement because of '[' having
double syntactical meaning.

For additional inspiration, you might want to look at XSLT
which provides similar transformations on XML data structures.

There are also a number of other transformation languages:

http://en.wikipedia.org/wiki/Model_Transformation_Languagehttp://en.wikipedia.org/wiki/Data_transformation

Thanks for the links!

Regarding the term DDL: that's normally used for data definition
language and doesn't really have all that much to do with
transforming data. You normally define data structures using
DDL - without actually putting data into those structures.

Why not PyDTL Python data transformation language ?!

Yep, I like that suggestion. The language does indeed describe a
transformation. In some ways I was wanting to think of it more
broadly, in terms that the transformation also acts as a schema for
any input objects. For example, you could use '{.title, .publisher,
{.name} }' as a schema to validate that an object behaves like a
book. I suppose that's still a transformation in an abstract sense,
where the output is just True, False, or maybe even the slice of the
transformation that can/cannot be executed.

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Re: using struct module on a file

2009-11-18 Thread Jon Clements

On Nov 18, 4:42 pm, Ulrich Eckhardt dooms...@knuut.de wrote:
 Hia!

 I need to read a file containing packed binary data. For that, I find the
 struct module pretty convenient. What I always need to do is reading a chunk
 of data from the file (either using calcsize() or a struct.Struct instance)
 and then parsing it with unpack(). For that, I repeatedly write utility
 functions that help me do just that, but I can't imagine that there is no
 better way for that.

 Questions:
 0. Am I approaching this from the wrong direction? I'm not a programming
 noob, but rather new to Python still.
 1. The struct module has pack_into() or unpack_from(), could I somehow
 combine that with a file?
 2. Is there some easier way to read files? I know about array and xdrlib,
 but neither really fit my desires.
 3. Failing all that, would you consider this a useful addition to the struct
 module, i.e. should I write a feature request?

 Thanks!

 Uli

First time I've seen zero based indexing for paragraph markers :)

unpack_from() will work on anything that supports the buffer
interface.

To work with files you can use something like:

my4chars = struct.Struct('4c')
def struct_read(s, f):
  return s.unpack_from(f.read(s.size))

Which isn't hideously painful.

Jon.



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Re: _winreg error on open key (64bit) - proper usage of _winreg.DisableReflectionKey

2009-11-18 Thread Brian Curtin

On Tue, Nov 17, 2009 at 19:59, Mark Hammond skippy.hamm...@gmail.comwrote:

 On 18/11/2009 6:29 AM, Randall Walls wrote:

 I don't believe so, but it seems like I'm in a catch 22, where I need to
 _winreg.OpenKey the key first before I can pass it to
 _winreg.DisableReflectionKey, but it doesn't exist, so I can't open it.

 I did find out that I can open the key using:
 hKey = _winreg.OpenKey(_winreg.HKEY_LOCAL_MACHINE,
 rSOFTWARE\ODBC\ODBC.INI\
 DRSQL2000_mu0100\\, 0, _winreg.KEY_READ | _winreg.KEY_WOW64_64KEY)

 The 'trick' was adding _winreg.KEY_WOW64_64KEY, which apparently tells
 the system to look in the 64bit key area, and not under the Wow6432Node.
 That brings up problem #2, though... I can't seem to CREATE a key in the
 above path, and _winreg.CreateKey doesn't accept _winreg.KEY_WOW64_64KEY
 (in fact it doesn't accept any options other than key, sub_key).
 _winreg.CreateKey does work, it just puts the key in
 SOFTWARE\Wow6432Node\ODBC\ODBC.INI. So I'm in a quandry... I'd like to
 use one or the other, and not have to account for both.


 It looks like _winreg needs to be enhanced to make the RegCreateKeyEx API
 function available.  It can be called via the win32api module of pywin32, or
 could also be called via ctypes.

 HTH,

 Mark


Created http://bugs.python.org/issue7347 and added a patch which I think
will solve the problem moving forward.
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Re: IOError: [Errno 28] No space left on device



--- On Wed, 11/18/09, Grant Edwards inva...@invalid.invalid wrote:

 From: Grant Edwards inva...@invalid.invalid
 Subject: Re: IOError: [Errno 28] No space left on device
 To: python-list@python.org
 Date: Wednesday, November 18, 2009, 9:22 AM
 On 2009-11-18, hong zhang henryzhan...@yahoo.com
 wrote:
 
  Apparently the harddisk where you stored the file
 is full?
 
 It's not a real file, and takes up no space.
 
  I have plenty space see:
  $ df -l
  Filesystem       
    1K-blocks      Used
 Available Use% Mounted on
  /dev/sda1         
    74027808   4910016 
 65357380   7% /
 
 That doesn't matter.  /sys doesn't contain real
 files.  It's an
 API to access kernel internals.
 
  but following is good.
 
  cont_tx = 1
  for i in
 glob.glob('/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx'):
       with open(i, 'w') as f:
           print f,
 cont_tx
 
 Well, if that works, then what's your problem?

But error comes from following, above is good. That is point here.

def do_cont_tx( is_start):
global cont_tx_started, stdscr
if is_start == START and not cont_tx_started:
cont_tx = 1
for i in 
glob.glob('/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx'):
with open(i, 'w') as f:
print f, cont_tx -- 

                
            
    visi.com         
   PREVIOUS LIFE as a COMPLETE
                
                
                
    STRANGER?
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DOM related question and problem

2009-11-18 Thread elca


Hello,
these day im making python script related with DOM.

problem is these day many website structure is very complicate .

what is best method to check DOM structure and path..

i mean...following is some example.

what is best method to check  can extract such like following info quickly?

before i was spent much time to extract such info .

and yes im also new to python and DOM.

IE.Document.Frames(1).Document.forms('comment').value = 'hello'

if i use DOM inspector, can i extract such info quickly ? if so would you
show me some sample?

here is some site . i want to extract some dom info. 

today i was spent all day long to extract what is dom info. but failed

http://www.segye.com/Articles/News/Politics/Article.asp?aid=20091118001261ctg1=06ctg2=00subctg1=06subctg2=00cid=010101060

at the end of this page,can find some comment input box.

i want to know what kind of dom element should have to use, such like 

IE.Document.Frames(1).Document.forms('comment').value = 'hello'

anyhelp much appreciate thanks


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Re: ANN: Urwid 0.9.9 - Console UI Library

2009-11-18 Thread Chris Jones

I noticed that when run on a 256-color capable xterm, upon exiting the
demo programs the colors in the bash shell are modified - e.g the bash
prompt, the output of colored ls commands. 

For instance, due to my fiddling with dircolors, a file with executable
flags on is normally displayed in light green and it now appears in
bright green, presumably #00ff00.

CJ



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Re: DOM related question and problem

On Wed, Nov 18, 2009 at 10:04 AM, elca high...@gmail.com wrote:
 Hello,
 these day im making python script related with DOM.

 problem is these day many website structure is very complicate .

 what is best method to check DOM structure and path..

 i mean...following is some example.

 what is best method to check  can extract such like following info quickly?

 before i was spent much time to extract such info .

 and yes im also new to python and DOM.

    IE.Document.Frames(1).Document.forms('comment').value = 'hello'

 if i use DOM inspector, can i extract such info quickly ? if so would you
 show me some sample?

 here is some site . i want to extract some dom info.

 today i was spent all day long to extract what is dom info. but failed

 http://www.segye.com/Articles/News/Politics/Article.asp?aid=20091118001261ctg1=06ctg2=00subctg1=06subctg2=00cid=010101060

 at the end of this page,can find some comment input box.

 i want to know what kind of dom element should have to use, such like

    IE.Document.Frames(1).Document.forms('comment').value = 'hello'

 anyhelp much appreciate thanks

This sounds suspiciously like a spambot. Why do you want to submit
comments in an automated fashion exactly?

Cheers,
Chris
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Re: break LABEL vs. exceptions + PROPOSAL

2009-11-18 Thread Terry Reedy


Chris Rebert wrote:

On Wed, Nov 18, 2009 at 4:05 AM, Lo'oris loo...@gmail.com wrote:

I've found this email, back from 10 years ago:
http://mail.python.org/pipermail/python-list/1999-September/009983.html

I guess it went unnoticed, because that proposal looks really
intresting.


I think it went unnoticed because it is not very good, once looked at.


• break labels have been refused into python
• we can do it anyway using exceptions


So the proposal is not needed


• this is a proposal for something better, resembling the exception
way and much more powerful and python-like than break labels


It amounts to duplicating raise x...exception x as break xcontinue x 
in the name of aesthetics and supposed efficiency. There would be no new 
functionality nor any abbreviation of code. The semantics of 
break/continue as specific loop subcommands would be changed to 'use 
anyplace'. The OP gives as a reason the possibility of a typo creating a 
raise x ... except y mis-match. But a break x ... continue y mismatch is 
equally likely.


Anyway, I think the example given would be better written with immediate 
assignment followed by simple break, rather than the proposed delayed 
assignment.


The exception example as given would have to be rewritten to work in 3.x.


You're gonna have to wait 18-24 months:
http://www.python.org/dev/peps/pep-3003/

Also, the python-ideas list might be a better forum for discussing
this than the general-interest list:
http://mail.python.org/mailman/listinfo/python-ideas


This is a fine place to discuss it.

Terry Jan Reedy


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Re: IOError: [Errno 28] No space left on device

2009-11-18 Thread Diez B. Roggisch

hong zhang wrote:

 
 
 --- On Wed, 11/18/09, Grant Edwards inva...@invalid.invalid wrote:
 
 From: Grant Edwards inva...@invalid.invalid
 Subject: Re: IOError: [Errno 28] No space left on device
 To: python-list@python.org
 Date: Wednesday, November 18, 2009, 9:22 AM
 On 2009-11-18, hong zhang henryzhan...@yahoo.com
 wrote:
 
  Apparently the harddisk where you stored the file
 is full?
 
 It's not a real file, and takes up no space.
 
  I have plenty space see:
  $ df -l
  Filesystem
 1K-blocks      Used
 Available Use% Mounted on
  /dev/sda1
 74027808   4910016
 65357380   7% /
 
 That doesn't matter.  /sys doesn't contain real
 files.  It's an
 API to access kernel internals.
 
  but following is good.
 
  cont_tx = 1
  for i in
 glob.glob('/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx'):
 with open(i, 'w') as f:
 print f,
 cont_tx
 
 Well, if that works, then what's your problem?
 
 But error comes from following, above is good. That is point here.
 
 def do_cont_tx( is_start):
 global cont_tx_started, stdscr
 if is_start == START and not cont_tx_started:
 cont_tx = 1
 for i in
 glob.glob('/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx'):
 with open(i, 'w') as f: print f, cont_tx --

cont_x -- doesn't work. So the above can't be the actual code.

Diez
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Re: Minimally intrusive XML editing using Python

2009-11-18 Thread Anthra Norell


Thomas Lotze wrote:

Chris Rebert wrote:

  

Have you considered using an XML-specific diff tool such as:



I'm afraid I'll have to fall back to using such a thing if I don't find a
solution to what I actually want to do.

I do realize that XML isn't primarily about its textual representation, so
I guess I shouldn't be surprised if what I'm looking for doesn't exist.
Still, it would be nice if it did...

  

Thomas,
  I just might have what you are looking for. But I want to be sure I 
understand your problem. So, please show a small sample and explain how 
you want it modified.

Frederic
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Re: Command line arguments??

2009-11-18 Thread Nobody

On Tue, 17 Nov 2009 23:57:55 +, Rhodri James wrote:

 Quote the filenames or escape the spaces:

 C:\Python26\Python.exe C:\echo.py C:\New Folder\text.txt

 We've been living with this pain ever since windowed GUIs encouraged  
 users
 to put spaces in their file names (Apple, I'm looking at you!).
 Fundamentally, if people want the pretty they have to live with the
 consequences.

 We've been living with much worse ever since Unix allowed users to put
 not only spaces but even newlines in their filenames.
 
 You'll notice I said encouraged, not allowed.

You'll notice I said allowed, not encouraged.

Code which can't handle spaces in filenames is broken from the outset; it
doesn't suddenly break the first time that someone passes a filename
containing spaces.

I have a suspicion that Win95 put spaces in two of the most important
directory names specifically to force developers to deal with this.

Nowadays, any Windows program which cannot handle spaces in pathnames is
usually a port of a Unix program (and a shoddy one at that).

OTOH, I'm surprised at how much Windows software still cannot handle
filenames outside of the system codepage (i.e. it's using the
byte-oriented API rather than the Unicode API).

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Re: Calling Python functions from Excel

2009-11-18 Thread Cannonbiker

On 18 lis, 03:09, Mark Tolonen metolone+gm...@gmail.com wrote:
 Chris Withers ch...@simplistix.co.uk wrote in message

 news:4b02d1e3.6080...@simplistix.co.uk...

  Mark Tolonen wrote:

  Please I need Calling Python functions from Excel and receive result
  back in Excel. Can me somebody advise simplest solution please? I am
  more VBA programmer than Python.

  Tryhttp://code.google.com/p/pyinex/

  The book Python: Programming on Win32 has a whole chapter on COM, and a
  section on COM servers.

  ...and it's generally accepted that COM sucks rocks through straws, so
  explore alternatives when they're available ;-)

  Chris

 True, but as usual Python makes it pretty darn easy (requires PyWin32):

 - ex.py ---
 class Example(object):
     _public_methods_ = ['Add','Mul']
     _reg_progid_ = 'MyPython.Example'
     _reg_clsid_ = '{insert_GUID_here}'

     def Add(self,a,b):
         return a+b

     def Mul(self,a,b):
         return a*b

 if __name__ == '__main__':
     import win32com.server.register
     win32com.server.register.UseCommandLine(Example)
 -

 -- Excel Macro --
 Sub Testit()
     Set ex = CreateObject(MyPython.Example)
     Range(A1) = ex.Add(1, 2)
     Range(A2) = ex.Mul(3, 4)
 End Sub
 

 Just run the script to register the server.  ex.py --unregister will
 remove it.

 -Mark

Thanks very much. It works perfectly!!! :-)
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Re: getting properly one subprocess output

2009-11-18 Thread Nobody

On Wed, 18 Nov 2009 12:25:14 +0100, Jean-Michel Pichavant wrote:

 I'm currently inspecting my Linux process list, trying to parse it in 
 order to get one particular process (and kill it).
 I ran into an annoying issue:
 The stdout display is somehow truncated (maybe a terminal length issue, 
 I don't know), breaking my parsing.

 As you can see, to complete process command line is truncated.
 Any clue on how to get the full version ?

If you only need it to work on Linux, you can just enumerate 
/proc/[1-9]*/exe or /proc/[1-9]*/cmdline.

Or you can add -ww to ps to avoid truncating the output.

Note that the /proc/*/exe report the actual executable. The command line
reported by ps (from /proc/*/cmdline) can be modified by the program, so
it doesn't necessarily reflect the program being run.


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Re: non-copy slices

2009-11-18 Thread Terry Reedy


tbour...@doc.ic.ac.uk wrote:

Hi,

I was looking for a facility similar to slices in python library that 
would avoid the implicit creation of a new list and copy of elements 
that is the default behaviour. Instead I'd rather have a lazy iteratable 
object on the original sequence. Well, in the end I wrote it myself but 
I was wondering if I missed sth in the library  If I didn't is there a
particular reason there isn't sth like that? I find it hard to believe 
that all slice needs have strictly copy semantics.


It is a strict *shallow* copy. There is no copying of contents.
That aside, you are right, hence itertools.islice as already mentioned. 
In the design of 3.0, I believe the idea was raised of making slices 
iterables in 3.0, just as was done for map, filter, and range. However, 
it would have been highly disruptive, and not save much space. Map and 
range create an unbounded number of new objects, rather than just a 
sequence of references to existing objects (or bytes or words for bytes 
and str slices). There is also the problem of virtual slices preventing 
garbage collection of the source sequence when it is not otherwise needed.


Terry Jan Reedy

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Re: IOError: [Errno 28] No space left on device



--- On Wed, 11/18/09, Grant Edwards inva...@invalid.invalid wrote:

 From: Grant Edwards inva...@invalid.invalid
 Subject: Re: IOError: [Errno 28] No space left on device
 To: python-list@python.org
 Date: Wednesday, November 18, 2009, 9:22 AM
 On 2009-11-18, hong zhang henryzhan...@yahoo.com
 wrote:
 
  Apparently the harddisk where you stored the file
 is full?
 
 It's not a real file, and takes up no space.
 
  I have plenty space see:
  $ df -l
  Filesystem       
    1K-blocks      Used
 Available Use% Mounted on
  /dev/sda1         
    74027808   4910016 
 65357380   7% /
 
 That doesn't matter.  /sys doesn't contain real
 files.  It's an
 API to access kernel internals.
 
  but following is good.
 
  cont_tx = 1
  for i in
 glob.glob('/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx'):
       with open(i, 'w') as f:
           print f,
 cont_tx
 
 Well, if that works, then what's your problem?

But error comes from following, above is good. That is point here.

def do_cont_tx( is_start):
global cont_tx_started, stdscr
if is_start == START and not cont_tx_started:
cont_tx = 1
for i in 
glob.glob('/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx'):
with open(i, 'w') as f:
print f, cont_tx 


  
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Re: IOError: [Errno 28] No space left on device

--- On Wed, 11/18/09, Diez B. Roggisch de...@nospam.web.de wrote:

 From: Diez B. Roggisch de...@nospam.web.de
 Subject: Re: IOError: [Errno 28] No space left on device
 To: python-list@python.org
 Date: Wednesday, November 18, 2009, 12:11 PM
 hong zhang wrote:

  --- On Wed, 11/18/09, Grant Edwards inva...@invalid.invalid
 wrote:

  From: Grant Edwards inva...@invalid.invalid
  Subject: Re: IOError: [Errno 28] No space left on
 device
  To: python-list@python.org
  Date: Wednesday, November 18, 2009, 9:22 AM
  On 2009-11-18, hong zhang henryzhan...@yahoo.com
  wrote:

   Apparently the harddisk where you stored
 the file
  is full?

  It's not a real file, and takes up no space.

   I have plenty space see:
   $ df -l
   Filesystem
  1K-blocks      Used
  Available Use% Mounted on
   /dev/sda1
  74027808   4910016
  65357380   7% /

  That doesn't matter.  /sys doesn't contain real
  files.  It's an
  API to access kernel internals.

   but following is good.

   cont_tx = 1
   for i in

 glob.glob('/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx'):
  with open(i, 'w') as f:
  print f,
  cont_tx

  Well, if that works, then what's your problem?

  But error comes from following, above is good. That is
 point here.

  def do_cont_tx( is_start):
  global cont_tx_started, stdscr
  if is_start == START and not cont_tx_started:
  cont_tx = 1
  for i in

 glob.glob('/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx'):
  with open(i, 'w') as f: print f, cont_tx --

 cont_x -- doesn't work. So the above can't be the actual
 code.

Sorry, -- is typo.

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Re: Minimally intrusive XML editing using Python

2009-11-18 Thread Dave Angel


Thomas Lotze wrote:

Chris Rebert wrote:

  

Have you considered using an XML-specific diff tool such as:



I'm afraid I'll have to fall back to using such a thing if I don't find a
solution to what I actually want to do.

I do realize that XML isn't primarily about its textual representation, so
I guess I shouldn't be surprised if what I'm looking for doesn't exist.
Still, it would be nice if it did...

  
What's your real problem, or use case?  Are you just concerned with 
diffing, or are others likely to read the xml, and want it formatted the 
way it already is?  And how general do you need this tool to be?  For 
example, if the only thing you're doing is modifying existing attributes 
or existing tags, the minimal change would be pretty unambiguous.  But 
if you're adding tags, or adding content on what was an empty element, 
then the requirement gets fuzzy  And finding an existing library for 
something fuzzy is unlikely.


Sample input, change list, and desired output would be very  useful.

DaveA

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Re: Minimally intrusive XML editing using Python

2009-11-18 Thread Nobody

On Wed, 18 Nov 2009 13:55:52 +0100, Thomas Lotze wrote:

 I wonder what Python XML library is best for writing a program that makes
 small modifications to an XML file in a minimally intrusive way. By that I
 mean that information the program doesn't recognize is kept, as are
 comments and whitespace, the order of attributes and even whitespace
 around attributes. In short, I want to be able to change an XML file while
 producing minimal textual diffs.
 
 Most libraries don't allow controlling the order of and the whitespace
 around attributes, so what's generally left to do is store snippets of
 original text along with the model objects and re-use that for writing the
 edited XML if the model wasn't modified by the program. Does a library
 exist that helps with this? Does any XML library at all allow structured
 access to the text representation of a tag with its attributes?

Expat parsers have a CurrentByteIndex field, while SAX parsers have
locators. You can use this to identify the portions of the input which
need to be processed, and just copy everything else. One downside is that
these only report either the beginning (Expat) or end (SAX) of the tag;
you'll have to deduce the other side yourself.

OTOH, diff is probably the wrong tool for the job.

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Re: python gui builders

2009-11-18 Thread Dave Cook

On 2009-11-18, sturlamolden sturlamol...@yahoo.no wrote:

 GPL

If it's an issue for your project, I suggest wxPython.  It's
cross-platform, fairly complete, and extensible.  But the API is
clunky compared to Qt.

Dave Cook
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A Good Mailer

2009-11-18 Thread Victor Subervi

Hi;
I need a good mailer that will enable me to mail email from web forms.
Suggestions?
TIA,
Victor
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Re: WindowsError is not available on linux?

2009-11-18 Thread Aahz

In article mailman.599.1258510702.2873.python-l...@python.org,
Peng Yu  pengyu...@gmail.com wrote:

It's not clear to me whether WindowsError is available on linux or
not, after I read the document. 

Here's what I told a co-worker to do yesterday:

if os.name == 'nt':
DiskError = (OSError, WindowsError)
else:
DiskError = WindowsError

try:
disk_operation()
except DiskError:
logit()
-- 
Aahz (a...@pythoncraft.com)   * http://www.pythoncraft.com/

Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are, by
definition, not smart enough to debug it.  --Brian W. Kernighan
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Re: IOError: [Errno 28] No space left on device

2009-11-18 Thread Grant Edwards

On 2009-11-18, Diez B. Roggisch de...@nospam.web.de wrote:
 hong zhang wrote:
 
  but following is good.
 
  cont_tx = 1
  for i in
 glob.glob('/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx'):
 with open(i, 'w') as f:
 print f,
 cont_tx
 
 Well, if that works, then what's your problem?
 
 But error comes from following, above is good. That is point here.
 
 def do_cont_tx( is_start):
 global cont_tx_started, stdscr
 if is_start == START and not cont_tx_started:
 cont_tx = 1
 for i in
 glob.glob('/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx'):
 with open(i, 'w') as f: print f, cont_tx --

 cont_x -- doesn't work. So the above can't be the actual code.

You never want to post the actual code you're running.  That
would make it too easy for people to help.

-- 
Grant Edwards   grante Yow! My mind is making
  at   ashtrays in Dayton ...
   visi.com
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Re: Language mavens: Is there a programming with if then else ENDIF syntax?

2009-11-18 Thread Simon Forman

On Wed, Nov 18, 2009 at 4:15 AM, Steve Howell showel...@yahoo.com wrote:
 On the topic of switch statements and even-more-concise-then-we-have-
 already if/elif/else/end constructs, I have to say that Python does
 occasionally force you to write code like the code below.  Maybe
 force is too strong a word, but Python lends itself to if/elif
 blocks like below, which get the job done just fine, but which are not
 syntactically pretty, due to the (el){0,1}if kind == duplication.
 There are often cases where if/elif statements are just a smell that
 you do not know how to do dictionary lookups, but if you converted the
 below code to use dictionary lookups, you would complicate the code
 almost as much as you abstracted the code, if not more, unless I am
 just being very naive.  Anonymous methods would help to a certain
 degree.  I am not saying I want either anonymous methods or switch
 statements, but the lack of either in a language leads to very
 procedural looking code when you use number-of-lines-of-code as a
 (possibly dubious) metric.

 Maybe this excerpt can be golfed down to something simpler, I would
 love to see it!

        if kind == 'dict':
            return dictionary_schema(ast)
        elif kind == 'list':
            method = dictionary_schema(ast)
            return lambda lst: map(method, lst)
        elif kind == 'attr':
            return ((lambda obj: getattr(obj, ast.field)), ast.field)
        elif kind == 'key':
            return (lambda obj: obj.get(ast.field), ast.field)
        elif kind == 'as':
            method, old_name = schema(ast.parent)
            return (method, ast.synonym)
        elif kind == 'call':
            method, old_name = schema(ast.parent)
            def call(obj):
                return method(obj)()
            return (call, old_name)
        elif kind == 'recurse':
            expr = ast.expr
            kind = expr.kind
            method, field_name = schema(ast.parent)
            if kind in ['attr', 'key']:
                new_method, new_field_name = schema(expr)
                field_name = new_field_name
            elif kind in ['dict', 'list']:
                new_method = schema(expr)
            else:
                raise Exception('unknown kind!')
            def recurse(obj):
                obj = method(obj)
                return new_method(obj)
            return (recurse, field_name)
        else:
            raise Exception('unknown kind!')


This code is perhaps not a great example of your point.  Every
(el){0,1}if clause (other than the ones in the 'recurse' branch) end
in return statements, so the el's are pointless.

FWIW I might write it like so:

class ASTthing:

def processAST(self, ast, kind):
try:
method = getattr(self, 'do_' + kind)
except AttributeError:
raise Exception('unknown kind!')

self.ast = ast

return method()

def do_dict(self):
return dictionary_schema(self.ast)

def do_list(self):
method = dictionary_schema(self.ast)
return lambda lst: map(method, lst)

def do_attr(self):
field_name = self.ast.field
return lambda obj: getattr(obj, field_name), field_name

def do_key(self):
field_name = self.ast.field
return lambda obj: obj.get(field_name), field_name

def do_as(self):
method, old_name = schema(self.ast.parent)
return method, self.ast.synonym

def do_call(self):
method, old_name = schema(self.ast.parent)
return lambda obj: method(obj)(), old_name

def do_recurse(self):
expr = self.ast.expr
kind = expr.kind

method, field_name = schema(self.ast.parent)

if kind in 'attrkey':
new_method, field_name = schema(expr)

elif kind in 'dictlist':
new_method = schema(expr)

else:
raise Exception('unknown kind!')

def recurse(obj):
obj = method(obj)
return new_method(obj)

return recurse, field_name


IMO, that's more pythonic and less complicated.
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Re: Language mavens: Is there a programming with if then else ENDIFsyntax?

2009-11-18 Thread Dotan Cohen

 The OP explicitly said no block delimiters. Your example uses {..}, and
 doesn't have endif.


Just out of habit. I think that PHP, like C, lets you avoid the block
deliminators so long as the block all fits on one line.


-- 
Dotan Cohen

http://what-is-what.com
http://gibberish.co.il
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Re: non-copy slices

2009-11-18 Thread Themis Bourdenas

Sth else that I noticed as I started using islice. The name is somewhat
misleading. Having the slice part in the name I would expect it to imitate
the functionality of normal slices. Random access, sub-slicing etc. However,
it is only iteratable. Any particular reasons for that? My guess is that
it's inside the itertools so it's meant only for iteration and not random
access. However, as I told before the name implies the same functionality
while the only thing they share is iteration. It's nothing in the library
that completely imitates the slice without the copies, right?

Cheers,
Themis


On Wed, Nov 18, 2009 at 6:49 PM, Terry Reedy tjre...@udel.edu wrote:

 tbour...@doc.ic.ac.uk wrote:
  Hi,
 
  I was looking for a facility similar to slices in python library that
  would avoid the implicit creation of a new list and copy of elements
  that is the default behaviour. Instead I'd rather have a lazy iteratable
  object on the original sequence. Well, in the end I wrote it myself but
  I was wondering if I missed sth in the library  If I didn't is there a
  particular reason there isn't sth like that? I find it hard to believe
  that all slice needs have strictly copy semantics.

 It is a strict *shallow* copy. There is no copying of contents.
 That aside, you are right, hence itertools.islice as already mentioned.
 In the design of 3.0, I believe the idea was raised of making slices
 iterables in 3.0, just as was done for map, filter, and range. However,
 it would have been highly disruptive, and not save much space. Map and
 range create an unbounded number of new objects, rather than just a
 sequence of references to existing objects (or bytes or words for bytes
 and str slices). There is also the problem of virtual slices preventing
 garbage collection of the source sequence when it is not otherwise needed.

 Terry Jan Reedy

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Re: WindowsError is not available on linux?

2009-11-18 Thread Benjamin Kaplan

On Wed, Nov 18, 2009 at 2:53 PM, Aahz a...@pythoncraft.com wrote:
 In article mailman.599.1258510702.2873.python-l...@python.org,
 Peng Yu  pengyu...@gmail.com wrote:

It's not clear to me whether WindowsError is available on linux or
not, after I read the document.

 Here's what I told a co-worker to do yesterday:

 if os.name == 'nt':
    DiskError = (OSError, WindowsError)
 else:
    DiskError = WindowsError

 try:
    disk_operation()
 except DiskError:
    logit()
 --

Shouldn't that be the other way?
if os.name == 'nt':
DiskError = OSError, WindowsError
else :
DiskError = OSError


 Aahz (a...@pythoncraft.com)           *         http://www.pythoncraft.com/

 Debugging is twice as hard as writing the code in the first place.
 Therefore, if you write the code as cleverly as possible, you are, by
 definition, not smart enough to debug it.  --Brian W. Kernighan
 --
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Using setup.py for an application, not a library module.

2009-11-18 Thread John Nagle


Most of the documentation for setup.py assumes you're packaging a
library module. (Ref: http://docs.python.org/distutils/setupscript.html;)
How do you properly package an application?  What happens
on setup.py install?  Where does the application get installed?  Where does
the main program go?

  If I package and build my app, it packages properly, and
unpacks and builds into

Messager1.0/build/lib

which is appropriate for a library, but not an application.
Here's the setup file.


distutils.core.setup(
name='Messager',
description=Baudot Teletype RSS and SMS program,
version='1.0',
author=John Nagle,
author_email=na...@animats.com,
packages=['messager'],
requires=['pyserial', 'feedparser']
)


John Nagle
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Re: WindowsError is not available on linux?

2009-11-18 Thread exarkun


On 07:53 pm, a...@pythoncraft.com wrote:

In article mailman.599.1258510702.2873.python-l...@python.org,
Peng Yu  pengyu...@gmail.com wrote:


It's not clear to me whether WindowsError is available on linux or
not, after I read the document.


Here's what I told a co-worker to do yesterday:

if os.name == 'nt':
   DiskError = (OSError, WindowsError)
else:
   DiskError = WindowsError

try:
   disk_operation()
except DiskError:
   logit()


This isn't necessary.  WindowsError subclasses OSError.

Jean-Paul
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Re: python gui builders

2009-11-18 Thread Simon Hibbs

On 18 Nov, 07:51, sturlamolden sturlamol...@yahoo.no wrote:


 GPL

PyQT is GPL for now, but Qt itself is available under the LGPL as is
PySide. Eventualy PySide, which tracks the PyQT API, will supplant it
and the issue will be moot. For now it can be a problem, but PyQT
developer licenses are very afordable at only a few hundred dollars.
If a commercial project can't aford that, it's got problems.

Only you can know enough to make an informed decision. Wx does look
more usable than last time I used it for a project and is a fine
option too, for me though QT is the gold standard against all others
are measured, and generaly found wanting.

Simon Hibbs
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Re: IOError: [Errno 28] No space left on device

--- On Wed, 11/18/09, Grant Edwards inva...@invalid.invalid wrote:

 From: Grant Edwards inva...@invalid.invalid
 Subject: Re: IOError: [Errno 28] No space left on device
 To: python-list@python.org
 Date: Wednesday, November 18, 2009, 2:00 PM
 On 2009-11-18, Diez B. Roggisch
 de...@nospam.web.de
 wrote:
  hong zhang wrote:

   but following is good.

   cont_tx = 1
   for i in

 glob.glob('/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx'):
  with open(i, 'w') as f:
  print f,
  cont_tx

  Well, if that works, then what's your
 problem?

  But error comes from following, above is good.
 That is point here.

  def do_cont_tx( is_start):
  global cont_tx_started, stdscr
  if is_start == START and not cont_tx_started:
  cont_tx = 1
  for i in

 glob.glob('/sys/kernel/debug/ieee80211/phy*/iwlagn/data/continuous_tx'):
  with open(i, 'w') as f: print f, cont_tx
 --

  cont_x -- doesn't work. So the above can't be the
 actual code.

 You never want to post the actual code you're
 running.  That
 would make it too easy for people to help.

 -- 

It is typo.

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

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Re: WindowsError is not available on linux?

2009-11-18 Thread Christian Heimes

Dave Angel wrote:
 Worse, even if the exception cannot be thrown on a non-Windows 
 environment, leaving it undefined makes it very awkward to write 
 portable code.  An except clause that can never happen in a particular 
 environment is pretty innocent.  Or somebody can use a base class for 
 his except clause, to catch this error and other related ones.  But it 
 blows up if you explicitly use this exception.  I think that needs 
 documentation, at a minimum.

WindowsError is a subclass of OSError that contains additional Windows
specific error information. Just catch OSError and you are on the safe
side.

Christian

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Re: non-copy slices

2009-11-18 Thread Ethan Furman


tbour...@doc.ic.ac.uk wrote:

Hi,

I was looking for a facility similar to slices in python library that 
would avoid the implicit creation of a new list and copy of elements 
that is the default behaviour. Instead I'd rather have a lazy iteratable 
object on the original sequence. Well, in the end I wrote it myself but 
I was wondering if I missed sth in the library. If I didn't is there a 
particular reason there isn't sth like that? I find it hard to believe 
that all slice needs have strictly copy semantics.


Cheers,
Themis


Two questions:  1) What is sth?  and 2), What copy?

Python 2.5.4 (r254:67916, Dec 23 2008, 15:10:54) [MSC v.1310 32 bit (Intel)]
In [1]: class dummy(object):
   ...: pass
   ...:

In [2]: a = dummy()
In [3]: b = dummy()
In [4]: c = dummy()
In [5]: d = dummy()
In [6]: e = dummy()
In [7]: list1 = [a, b, c, d, e]
In [8]: list1
Out[8]:
[__main__.dummy object at 0x0130C510,
 __main__.dummy object at 0x013F1A50,
 __main__.dummy object at 0x00A854F0,
 __main__.dummy object at 0x00A7EF50,
 __main__.dummy object at 0x00A7E650]

In [9]: list2 = list1[1:3]
In [10]: list2
Out[10]:
[__main__.dummy object at 0x013F1A50,
 __main__.dummy object at 0x00A854F0]

In [11]: list2[0] is list1[1]
Out[11]: *True*
In [12]: list2[1] is list1[2]
Out[12]: *True*

No copying of items going on here.  What do you get?

~Ethan~
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Re: python gui builders

2009-11-18 Thread Simon Hibbs

On 17 Nov, 23:25, Kevin Walzer k...@codebykevin.com wrote:
 On 11/17/09 4:25 PM, Tim Daneliuk wrote:

  +1 Tkinter for the simple stuff

 You can actually use Tkinter to do quite sophisticated GUI's that rival
 anything found in Qt or wx...

Neither Tkinteror Wx have anything that come close to QGraphicsView,
the Model-View-Delegate framework, the Phonon multimedia framework
integration, QtSQL, QtXML, QtSVG, and the many other first grade
components in Qt. You can substitute components from other frameworks,
e.g. for database access, but then you lose the integration QtSQL has
with the model-view-delegate features in other parts of the Qt world.

Qt is much more than just a GUI framework, it's more of a rival to
something like the MacOS development libraries, or the .NET framework
in terms of the library facilities it offers. I think that's why Nokia
bought into it. Qt provides them with a platform with the potential to
rival the iPhone dev environment.

Of course to take full advantage of it you need to invest in learning
it all, which is non-trivial. It comes at a cost in time and potential
lock-in. But the point is you can't just say Qt is just like Wx.

Simon Hibbs
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Re: python gui builders

2009-11-18 Thread David Bolen

Simon Hibbs simon.hi...@gmail.com writes:

 I've had this problem for a few years. I've tried PythonCard,
 WxWidgets with WxDesigner, BoaConstructor, etc. None of them come
 anywhere close to PyQT/QTDesigner.

For me, the killer feature missing from of all of the wx-based
designers is that they require sizer based designs at all stages, not
even permitting a fixed layout up front as a first draft.  Either that
or any case I've found permitting a fixed layout, then didn't permit
turning that easily into a sizer-based layout.

From an overall design perspective, that was the feature I found most
intriguing in QTDesigner.  I could randomly drop stuff around the
window while doing an initial layout, which is especially helpful when
you aren't quite sure yet how you want the layout to look.  Then you
can select groups of objects and apply the containers to provide for
flexible layout.

I absolutely prefer sizer-based layouts for a final implementation,
but early in the design stages find it more helpful, and freeing, not
to be as tied to the containers.

With that said, for various reasons I still prefer wxPython to Qt, and
at the moment, find wxFormBuilder the best fit for my own designs
(even before the direct Python support, just using XRC).

-- David
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Re: Language mavens: Is there a programming with if then else ENDIF syntax?

2009-11-18 Thread Steven D'Aprano

On Wed, 18 Nov 2009 09:33:38 +0200, Dotan Cohen wrote:

 Is there any particular reason why this might be a *bad* language-
 design idea?
 
 It is about as far from OO as one could get. Whether or not that is
 bad depends on the use case.


That's crazy talk. IF...ENDIF is *syntax*, not a programming model. How 
is this hypothetical Python-like syntax not object oriented?

class Parrot:
def speak(self):
if self.name is None:
name = Polly
else:
name = self.name
endif
return %s wants a cracker! % name


Syntax controls *how* you instruct the compiler, the programming model 
controls *what* you instruct the compiler to do.



-- 
Steven
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Re: WindowsError is not available on linux?

2009-11-18 Thread Dave Angel




Benjamin Kaplan wrote:

On Wed, Nov 18, 2009 at 2:53 PM, Aahz a...@pythoncraft.com wrote:
  

In article mailman.599.1258510702.2873.python-l...@python.org,
Peng Yu  pengyu...@gmail.com wrote:


It's not clear to me whether WindowsError is available on linux or
not, after I read the document.
  

Here's what I told a co-worker to do yesterday:

if os.name ='nt':
   DiskError =OSError, WindowsError)
else:
   DiskError =indowsError

try:
   disk_operation()
except DiskError:
   logit()
--



Shouldn't that be the other way?
if os.name ='nt':
DiskError =SError, WindowsError
else :
DiskError =SError


  
Doesn't matter.  It's not needed anyway, since WindowsError is derived 
from OSError.   So just use OSError in the except clause.


DaveA

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Solved: Inserting Unicode text with MySQLdb in Python 2.4-2.5?

2009-11-18 Thread Threader Slash

-- Forwarded message --
From: Keith Hughitt keith.hugh...@gmail.com
To: python-list@python.org
Date: Wed, 18 Nov 2009 06:09:11 -0800 (PST)
Subject: Inserting Unicode text with MySQLdb in Python 2.4-2.5?
Hi all,

I ran into a problem recently when trying to add support for earlier
versions of Python (2.4 and 2.5) to some database related code which
uses MySQLdb, and was wondering if anyone has any suggestions.

With later versions of Python (2.6), inserting Unicode is very simple,
e.g.:

   # -*- coding: utf-8 -*-
   ...
   cursor.execute('''INSERT INTO `table` VALUES (0,
'Ångström'),...''')

When the same code is run on earlier versions, however, the results is
either garbled text (e.g. Ã or ? instead of Å in Python 2.5), or
an exception being thrown (Python 2.4):

   UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in
position 60: ordinal not in range(128)

So far I've tried a number of different things, including:

   1. Using Unicode strings (e.g. u\u212B)

   2. Manually specifying the encoding using sys.setdefaultencoding
('utf-8')

   3. Manually enabling Unicode support in MySQLdb
(use_unicode=False, charset = utf8)

...but no combination of any of the above resulted in proper database
content.

To be certain that the issue was related to Python/MySQLdb and not
MySQL itself, I manually inserted the text and it worked just fine.
Furthermore, when working in a Python console, both print Å and
print u\u212B display the correct output.

Any ideas? The versions of the MySQLdb adapter tested were 1.2.1
(Python 2.4), and 1.2.2-10 (Python 2.5).

Thanks!
Keith

Hello Keithm,

Here is your answer...

I run on Python2.5, this syntax works fine for me -- a piece of my code:

getMaxID_Query = SELECT MAX(customerID)
FROM customer;

self.cursorMySQL.execute(getMaxID_Query)

Try to use:  instead of ''' . It will solve your problem.

ThreaderSlash
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Re: python gui builders

2009-11-18 Thread Stef Mientki


Simon Hibbs wrote:

On 18 Nov, 07:51, sturlamolden sturlamol...@yahoo.no wrote:

  

GPL



PyQT is GPL for now, but Qt itself is available under the LGPL as is
PySide. Eventualy PySide, which tracks the PyQT API, will supplant it
and the issue will be moot. For now it can be a problem, but PyQT
developer licenses are very afordable at only a few hundred dollars.
If a commercial project can't aford that, it's got problems.

Only you can know enough to make an informed decision. Wx does look
more usable than last time I used it for a project and is a fine
option too, for me though QT is the gold standard against all others
are measured, and generaly found wanting.

Simon Hibbs
  

Wouldn't it be nice
if each fan of some form of GUI-package,
would post it's code (and resulting images) for generating one or two 
standard GUI-forms ?


Then everyone can judge the differences,
and see what's simple and not  so simple !!

And of course I'm willing to contribute the wxPython (wrapped in some 
convenience procedures) for it.


cheers,
Stef

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Re: Using setup.py for an application, not a library module.

2009-11-18 Thread Philip Semanchuk



On Nov 18, 2009, at 3:53 PM, John Nagle wrote:


   Most of the documentation for setup.py assumes you're packaging a
library module. (Ref: http://docs.python.org/distutils/setupscript.html 
)

How do you properly package an application?  What happens
on setup.py install?  Where does the application get installed?   
Where does

the main program go?

 If I package and build my app, it packages properly, and
unpacks and builds into

Messager1.0/build/lib

which is appropriate for a library, but not an application.
Here's the setup file.


distutils.core.setup(
name='Messager',
description=Baudot Teletype RSS and SMS program,
version='1.0',
author=John Nagle,
author_email=na...@animats.com,
packages=['messager'],
requires=['pyserial', 'feedparser']
   )


Hi John,
I'm not sure what part you find unpalatable other than lib being in  
the pathname. I recently wrote a setup.py for an app called Analysis.  
Under OS X, Linux and Windows it installs into the site-packages  
directory so I can run it like so:


python C:\Python25\Lib\site-packages\analysis\main.py

or:

python /usr/local/lib/python2.6/dist-packages/analysis/main.py


Now, packaging an application according to the expectations of the  
platform to provide a double-clickable icon will require something  
like py2exe or py2app. distutils doesn't provide a facility for that.


DOes that give you an idea about what you were asking?

bye
Philip




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Re: A Good Mailer

2009-11-18 Thread Nick Stinemates

On Wed, Nov 18, 2009 at 03:27:11PM -0400, Victor Subervi wrote:
 Hi;
 I need a good mailer that will enable me to mail email from web forms.

smtplib

 Suggestions?

silly example..

#!/usr/bin/env python
import smtplib

session = smtplib.SMTP(localhost)
username = abc
password = def
session.login(username, password) # only if it requires auth

subject = Hello, 

header = Subject: %s \r\nContent-type: text/html;
charset=utf-8\r\n\r\n

message = world!

email_from = vic...@is.awesome
email_to = [em...@myhost.com]

session.sendmail(email_from, email_to, header+messages)

HTH,
Nick Stinemates


 TIA,
 Victor

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Re: using struct module on a file

2009-11-18 Thread Simon Forman

On Wed, Nov 18, 2009 at 11:42 AM, Ulrich Eckhardt dooms...@knuut.de wrote:
 Hia!

 I need to read a file containing packed binary data. For that, I find the
 struct module pretty convenient. What I always need to do is reading a chunk
 of data from the file (either using calcsize() or a struct.Struct instance)
 and then parsing it with unpack(). For that, I repeatedly write utility
 functions that help me do just that, but I can't imagine that there is no
 better way for that.

 Questions:
 0. Am I approaching this from the wrong direction? I'm not a programming
 noob, but rather new to Python still.
 1. The struct module has pack_into() or unpack_from(), could I somehow
 combine that with a file?
 2. Is there some easier way to read files? I know about array and xdrlib,
 but neither really fit my desires.
 3. Failing all that, would you consider this a useful addition to the struct
 module, i.e. should I write a feature request?

 Thanks!

 Uli

You might look at Construct:

http://construct.wikispaces.com/

~Simon
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Re: python gui builders

2009-11-18 Thread Kevin Walzer


On 11/18/09 4:15 PM, Simon Hibbs wrote:

On 17 Nov, 23:25, Kevin Walzerk...@codebykevin.com  wrote:

On 11/17/09 4:25 PM, Tim Daneliuk wrote:


+1 Tkinter for the simple stuff


You can actually use Tkinter to do quite sophisticated GUI's that rival
anything found in Qt or wx...


Neither Tkinteror Wx have anything that come close to QGraphicsView,
the Model-View-Delegate framework, the Phonon multimedia framework
integration, QtSQL, QtXML, QtSVG, and the many other first grade
components in Qt. You can substitute components from other frameworks,
e.g. for database access, but then you lose the integration QtSQL has
with the model-view-delegate features in other parts of the Qt world.


A few points of response:

-I was focusing primarily on the UI bits, not the other parts of Qt. 
People tend to think that Tkinter only has labels, listboxes, buttons 
and menus: recent advances in Tk have greatly expanded and modernized 
the available widgets. There's also a rich econsystem of widget packages 
within Tk that can be wrapped in Tkinter.


-Qt's support for things like SQL and XML make sense in a Pythonic 
context mainly if you're focusing on their integration with other parts 
of Qt. Python has many of these things just fine on its own, as you 
doubtless know.




Qt is much more than just a GUI framework, it's more of a rival to
something like the MacOS development libraries, or the .NET framework
in terms of the library facilities it offers. I think that's why Nokia
bought into it. Qt provides them with a platform with the potential to
rival the iPhone dev environment.


Of course, and I certainly wasn't claiming otherwise.



Of course to take full advantage of it you need to invest in learning
it all, which is non-trivial. It comes at a cost in time and potential
lock-in. But the point is you can't just say Qt is just like Wx.



wxWidgets (the C++ library) has support for a lot of things other than 
UI bits, as well. wxPython itself is mainly a GUI library because the 
additional features of wxWidgets in C++ are redundant in Python.


--Kevin

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Code by Kevin
http://www.codebykevin.com
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Re: Using setup.py for an application, not a library module.

2009-11-18 Thread Alan Franzoni

On 11/18/09 9:53 PM, John Nagle wrote:
 Most of the documentation for setup.py assumes you're packaging a
 library module. (Ref: http://docs.python.org/distutils/setupscript.html;)
 How do you properly package an application?  What happens
 on setup.py install?  Where does the application get installed?  Where
 does
 the main program go?

Usually, just package the lib and from your main program (e.g. the
script that goes in /usr/bin, for instance), do just something like that:

#!/usr/bin/python
from mylib import main
import sys

sys.exit(main())


-- 
Alan Franzoni
contact me at pub...@[mysurname].eu
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Re: Language mavens: Is there a programming with if then else ENDIF syntax?

2009-11-18 Thread Steven D'Aprano

On Wed, 18 Nov 2009 01:53:50 -0800, Steve Howell wrote:

 On Nov 18, 1:32 am, Chris Rebert c...@rebertia.com wrote:
 On Wed, Nov 18, 2009 at 1:15 AM, Steve Howell showel...@yahoo.com
 wrote:
  On the topic of switch statements and
  even-more-concise-then-we-have- already if/elif/else/end constructs,
  I have to say that Python does occasionally force you to write code
  like the code below.  Maybe force is too strong a word, but Python
  lends itself to if/elif blocks like below, which get the job done
  just fine, but which are not syntactically pretty, due to the
  (el){0,1}if kind == duplication. There are often cases where
  if/elif statements are just a smell that you do not know how to do
  dictionary lookups, but if you converted the below code to use
  dictionary lookups, you would complicate the code almost as much as
  you abstracted the code, if not more, unless I am just being very
  naive.

 I'm gonna have to disagree and say using the dictionary dispatch
 technique would clean it up a good bit. Yes, it would entail creating
 several functions, but those functions could then be documented (vs.
 the currently opaque code blocks); and due to their separation and
 smaller length, they would be easier to understand and test than the
 given code. Additionally, the sheer length of the given code segment
 probably constitutes a code smell in and of itself for the function
 containing that code.


 If you introduce seven tiny little methods, aren't you increasing the
 length of the module by seven lines and introducing more complexity with
 the dispatch mechanism? (Actually, it's 14 lines more if you put a line
 of whitespace between your methods, and then you are also blurring an
 important cue that each of the seven code blocks all perform within the
 same context.)


Dear me, the 1960s called, they want their controversy over structured 
programming back *wink*

Yes, you increase the length of the module by having function headers. 
You also increase the length of the module by using meaningful names 
instead of calling everything a, b, c etc. We're not playing code 
golf, there's no reward for making unreadable code.

The dispatch mechanism is no more complicated than a series of if...elif 
statements. In fact, you can replace an arbitrary number of if x == y 
statements with a *single* lookup:

if x == 1:
return 27
elif x == 2:
return 14
elif x == 5:
return 7
else:
return -1

becomes the single line:

return {1: 27, 2: 14, 5: 7}.get(x, -1)

(although for more complicated examples, you would put the dict into its 
own line, or even lines).

Dispatching isn't a panacea. You can't (easily) replace a series of 
if...elif statements where the conditions being tested aren't equality 
tests, e.g.:

if 0 = x = 1:
return 27
elif 1  x  1.5 or x == 2:
return 14
elif ...

is hard to turn into a dispatcher. But it's still a very useful technique 
when it applies.



 I do agree with your point that separate methods lead to easier unit
 testing.
 
 I'm a little more skeptical about the documentation/understanding
 argument, since code is often best understood within the context of
 surrounding code.

That depends on the code. In particular, it depends on how coupled the 
code is. Ideally, you should have loosely coupled code, not highly 
coupled. If the code is loosely coupled, then there's no problem with 
understanding it in isolation. If the code is highly coupled, then it is 
hard to refactor it into a separate function, but that's a side-effect of 
the original problem, namely the high degree of coupling.

As a general rule, if you need to know the context of the surrounding 
code to understand a function, you have too much coupling.



 I am also a bit skeptical of any coding technique
 that leads to lexical duplication like {'attr': process_attr, 'key':
 process_key, 'call': process_call}(ast); that is just replacing one
 smell with another.

But how is that different from this?

if condition(x, 'attr'):
return process_attr(x)(ast)
elif condition(x, 'key'):
return process_key(x)(ast)
elif ...


Lexical duplication is one of the weakest code smells around, because it 
is so prone to false negatives. You often can't avoid referring to the 
same lexical element multiple times:


def sinc(x):
if x != 0:
return sin(x)/x
return 1

That's four references to x in a four line function. Is this a problem? 
No, of course not.



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Re: New syntax for blocks

2009-11-18 Thread Steven D'Aprano

On Wed, 18 Nov 2009 18:28:11 +1300, greg wrote:

 r wrote:
 I think the syntax was chosen because the alternatives are even worse
 AND since assignment is SO common in programming, would you *really*
 rather type two chars instead of one?
 
 Smalltalk solved the problem by using a left-arrow character for
 assignment. But they had an unfair advantage in being able to use a
 non-standard character set on their custom-built machines.
 
 We should be able to do a lot better now using Unicode. We could even
 heal the  vs != rift by using a real not-equal symbol!

The problem isn't with the available characters, but with *typing* them.

It is hard to enter arbitrary Unicode characters by the keyboard, which 
frankly boggles my mind. I don't know what the state of the art on Mac is 
these days, but in 1984s Macs had a standard keyboard layout that let you 
enter most available characters via the keyboard, using sensible 
mnemonics. E.g. on a US keyboard layout, you could get ≠ by holding down 
the Option key and typing =.

For me, I had to:

Click Start menu  Utilities  More Applications  KCharSelect.
Click through thirty-four(!) tables scanning by eye for the symbol I 
wanted.
Click the ≠ character.
Click To Clipboard.
Go back to my editor window and paste.



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Arcane question regarding white space, editors, and code collapsing

2009-11-18 Thread Wells

I work in TextMate a lot, which I generally love, but it's code
collapsing confounds me. Essentially you have to indent blank lines to
the proper level for the current block. Then it will collapse that
section as one section. If you have simply a new line, it will see it
as a break, and not collapse, though the python interpreter doesn't
care- it only cares about lines of actual code.

Is it... pythonic, then, to have these lines of tabs/spaces to support
code collapsing? Is it proper, improper, or irrelevant?

Thanks.
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Re: Arcane question regarding white space, editors, and code collapsing

2009-11-18 Thread Ben Finney

Wells we...@submute.net writes:

 Is it... pythonic, then, to have these lines of tabs/spaces to support
 code collapsing? Is it proper, improper, or irrelevant?

It's quite improper (though syntactically null, in Python) to have
trailing whitespace on lines. That includes blank lines.

One major reason is that trailing whitespace causes spurious invisible
differences between otherwise-identical lines when doing an automatic
comparison, which is done quite a lot in collaboration and version
control.

Fix your text editor (which may entail switching to a better text
editor) to respect blank lines and the conventions of the language.

-- 
 \  “Hey Homer! You're late for English!” “Pff! English, who needs |
  `\  that? I'm never going to England!” —Barney  Homer, _The |
_o__)Simpsons_ |
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Re: Language mavens: Is there a programming with if then else ENDIF syntax?