Re: ANN: equivalence 0.1

[Giuseppe Ottaviano]

Interesting.. it took me a while to figure out why the second case is
so much slower and you're right, it is indeed quadratic. I don't know
how likely would such pathological cases be in practice, given that
the preferred way to merge a batch of objects is
eq.merge(*xrange(10001)), which is more than 3 times faster than the
non-pathologic first case (and which I optimized even further to avoid
attribute lookups within the loop so it's more like 5 times faster
now). Also the batch version in this case remains linear even if you
merge backwards, eq.merge(*xrange(1,-1,-1)), or in any order for
that matter.


The example just showed what could happen if the merges are done in  
pathological order, it is not about batch merging. I think that  
pathological cases like this indeed show up in real cases: many  
algorithms of near duplicate elimination and clustering reduce to  
finding connected components of a graph whose edges are given as a  
stream, so you can't control their order.
With this implementation, every time a component sized N is given a  
second (or following) argument to merge, you pay Omega(N).



I am familiar with it and I will certainly consider it for the next
version; for now I was primarily interested in functionality (API) and
correctness.


Good :) 
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Re: Better performance

[Arnaud Delobelle]

Franck Y [EMAIL PROTECTED] writes:

 Hello Folks,

 I am facing a problem where i need to parse around 200 files, i have a
 bit of knowledge in PHP/Perl/Python (the magic P :-P)

 Which one would you suggest me since i have to generate a web
 interface ?
 And each one has his  area of 'work'


 Thanks for your help !

Python, of course.

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Re: Python's doc problems: sort

[szr]

szr wrote:
 Jürgen Exner wrote:
 Andrew Koenig [EMAIL PROTECTED] wrote:
 [EMAIL PROTECTED] wrote in message

 [Subject:  Python's doc problems: sort]
 I want to emphasize a point here, as i have done quite emphatically
 in the past. The Python documentation, is the world's worst
 technical

 And WTF does Python documentation have to do with Perl of Lisp?

 szr, do you still have any doubts about the nature of xahlee?

 I wasn't involved in this thread, but no, after that statement
 comparing Perl's and Python's docs, I no doubts.

* should have been, , I have no doubts.

-- 
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platypus in page header

[Laszlo Nagy]

Is it possible to use platypus in page header and footer? I need to 
create a document with long paragraphs but also I need to put tables and 
images in page header and multi line info in page footer with alignment etc.


Thanks,

  Laszlo

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Re: The Importance of Terminology's Quality

[szr]

Arne Vajhøj wrote:
 szr wrote:
 Arne Vajhøj wrote:
 szr wrote:
 Peter Duniho wrote:
 On Fri, 30 May 2008 22:40:03 -0700, szr [EMAIL PROTECTED]
 wrote:
 Arne Vajhøj wrote:
 Stephan Bour wrote:
 Lew wrote:
 } John Thingstad wrote:
 }  Perl is solidly based in the UNIX world on awk, sed, } 
 bash and C. I don't like the style, but many do.
 }
 } Please exclude the Java newsgroups from this discussion.

 Did it ever occur to you that you don't speak for entire news
 groups?
 Did it occur to you that there are nothing about Java in the
 above ?
 Looking at the original post, it doesn't appear to be about any
 specific language.
 Indeed.  That suggests it's probably off-topic in most, if not
 all, of the newsgroups to which it was posted, inasmuch as they
 exist for topics specific to a given programming language.
 Perhaps - comp.programming might of been a better place, but not
 all people who follow groups for specific languages follow a
 general group like that - but let me ask you something. What is it
 you really have against discussing topics with people of
 neighboring groups? Keep in mind you don't have to read anything
 you do not want to read. [1]
 I very much doubt that the original thread is relevant for the Java
 group.

 But the subthread Lew commente don was about Perl and Unix. That is
 clearly off topic.

 I agree with and understand what you are saying in general, but
 still, isn't it possible that were are people in the java group (and
 others) who might of been following the thread, only to discover
 (probably not right away) that someone decided to remove the group
 they were reading the thread from? I know I would not like that,
 even if it wasn't on topic at the branch.

 Personally, I find it very annoying to have to switch news groups in
 order to resume a thread and weed my way down the thread to where it
 left off before it was cut off from the previous group.

 I am relative tolerant towards threads that are a bit off topic, if
 the S/N ratio overall is good.

Agreed.

[...]

If a thread, that is cross-posted, branches off on a tangent that has 
nothing to do with one or more groups what so ever, then yes, it makes 
sense to prune the 'newsgroup:' list / set follow ups, but in this case, 
someone made one mention or so of 'Perl', which was being used as an 
example, and someone (lew) moved to have the Java group removed.

There was little reason to cut off the thread, when people very well may 
have been following it, over the utterance of one word, which was being 
used as an example. The bulk of the thread had to do with general 
programming, and suddenly writing the name of a language doesn't mean 
it's way off on a tangent.

I hope this clears up some waters.

Regards.

-- 
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Re: Better performance

[Bruno Desthuilliers]

Franck Y a écrit :

Hello Folks,

I am facing a problem where i need to parse around 200 files, i have a
bit of knowledge in PHP/Perl/Python (the magic P :-P)

Which one would you suggest me since i have to generate a web
interface ?
And each one has his  area of 'work'



And where's your performance problem ?

You don't give enough details to seriously answer your question, but 
Python is a good tool for file parsing and web development anyway...

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printf in python

[gianluca]

Hy, I've a problem with may python library generated with swig from C
code. I works and I can access all function but a  simèple function
that print a string don't work's.
The function is like this:
int PrintTEST()
{
 printf(TEST );
 return 1;
}

If I call the function (myDLL.PrintTEST() ) the function print only
the returned value, not the string TEST. Could anybody help me?

Thanks

Gianluca
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Re: php vs python

[Arnaud Delobelle]

Joel Koltner [EMAIL PROTECTED] writes:

 There's potentially a large difference between a good speaker of 
 English/German/etc. vs. eloquent.

 I'd tend to agree with Jerry that if you can write good code in
 one language, you can in pretty much any other as well... but that
 doesn't imply you're necessarily eloquent in any languages. :-)
 Eloquence is nice, but eradicating bad code in this world is about
 a million times more important than attempting to move people from
 good code to eloquent code.

This is wrong, because if you know well one language only, you tend to
think that the principles that underpin it are universal.  So you will
try to shoehorn these principles into any other language you use.

It's only when you have become reasonably proficient in a number of
conceptually different languages that you start to build a picture of
what a programming language is.

I understand that there are some sane practices that are useful to
know when programming in any language, but it is wrong to say that the
skill of programming can be reduced to that, the rest being syntax.
There is (hopefully!) a design behind the syntax, you have to
understand it to use the language well.

You may be great at building Turing machines.  That doesn't make you a
master of crafting lambda-expressions.

 To be Pythonic here, eloquent code would perhaps often have clear,
 clean list comprehensions used when good code would use a for
 loop but still be easy to follow as well and perfectly acceptable in
 the vast majority of cases.

I find that eloquent Python speakers often tend to write a for loop
when mere good ones will try to stick a list comprehension in!

Regards

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Formatting Output

[[EMAIL PROTECTED]]

Hi,

i am building a little script and i want to output a series of columns
more or less like this:

1  5  6
2  2  8
2  9  5

The matter is that i don't know in advance how many columns there will
be. By the way, each column will be actually FLOATs, not INTs. How can
i do this ? Any help welcome. Regards,

Victor
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Re: php vs python

[Duncan Booth]

Arnaud Delobelle [EMAIL PROTECTED] wrote:

 I find that eloquent Python speakers often tend to write a for loop
 when mere good ones will try to stick a list comprehension in!
 

+1 QOTW

-- 
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Writing HTML

[miller . paul . w]

I've searched the standard library docs, and, while there are a couple
options for *reading* HTML from Python, I didn't notice any for
*writing* it.  Does anyone have any recommendations (particularly ones
not listed on PyPI)?

Thanks
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Re: printf in python

[Hrvoje Niksic]

gianluca [EMAIL PROTECTED] writes:

 Hy, I've a problem with may python library generated with swig from C
 code. I works and I can access all function but a  simèple function
 that print a string don't work's.
 The function is like this:
 int PrintTEST()
 {
  printf(TEST );
  return 1;
 }

Finish the printed string with a newline, or call fflush(stdout).  By
default stdout is line-buffered when connected to interactive displays.
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How solid is PyPy?

[miller . paul . w]

I've been looking at PyPy recently, and I see it's reached version 1.0
(and supports language version 2.4).  Given that, I was wondering what
level of backwards-compatibility one can expect from future versions,
i.e. if I run code on, say, a translated stackless PyPy now, what is
the probability that it will run unmodified on PyPy 1.x, 2.x, etc.?

Thanks!
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Re: Writing HTML

[Marc 'BlackJack' Rintsch]

On Mon, 02 Jun 2008 01:03:05 -0700, miller.paul.w wrote:

 I've searched the standard library docs, and, while there are a couple
 options for *reading* HTML from Python, I didn't notice any for
 *writing* it.

I guess that's where the many templating engines are used.

Ciao,
Marc 'BlackJack' Rintsch
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Re: Formatting Output

[Marc 'BlackJack' Rintsch]

On Mon, 02 Jun 2008 00:34:09 -0700, [EMAIL PROTECTED] wrote:

 i am building a little script and i want to output a series of columns
 more or less like this:
 
 1  5  6
 2  2  8
 2  9  5
 
 The matter is that i don't know in advance how many columns there will
 be. By the way, each column will be actually FLOATs, not INTs. How can
 i do this ? Any help welcome. Regards,

Look at string methods, `join()` for example, and string formatting with
the ``%`` operator.

Ciao,
Marc 'BlackJack' Rintsch
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Re: Formatting Output

[Chris]

On Jun 2, 9:34 am, [EMAIL PROTECTED]
[EMAIL PROTECTED] wrote:
 Hi,

 i am building a little script and i want to output a series of columns
 more or less like this:

 1  5  6
 2  2  8
 2  9  5

 The matter is that i don't know in advance how many columns there will
 be. By the way, each column will be actually FLOATs, not INTs. How can
 i do this ? Any help welcome. Regards,

 Victor

import sys
float_list = [1.0, 5.0, 6.0, 2.0, 2.0, 8.0, 2.0, 9.0, 5.0]
num_columns = 3
for i,item in enumerate(float_list):
sys.stdout.write('%.4f\t' % item)
if not (i+1) % num_columns:
sys.stdout.write('\n')

Problem with this approach is it doesn't cater for instances where you
exceed the standard 80 characters for a terminal window.
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Re: Why does python not have a mechanism for data hiding?

[Antoon Pardon]

On 2008-05-24, Ben Finney [EMAIL PROTECTED] wrote:
 Sh4wn [EMAIL PROTECTED] writes:

 first, python is one of my fav languages, and i'll definitely keep
 developing with it. But, there's 1 one thing what I -really- miss:
 data hiding. I know member vars are private when you prefix them with
 2 underscores, but I hate prefixing my vars, I'd rather add a keyword
 before it.

 From whom are you trying to hide your attributes?

 In Python, the philosophy we're all consenting adults here applies.
 You shouldn't pretend to know, at the time you write it, all the uses
 to which your code will be put. Barriers such as enforced private
 attributes will only cause resentment when people, despite your
 anticipations, *need* to access them and are then forced to hack their
 way around them.

I don't find this argument very compelling.

You can't anticipate all functionality people would like your function
to have. Acces to information in a (private) attribute is just one of
those possible functionallities. People will resent you if you don't
provide functionality they think fits logically in your package.

 If you want the users of your code to know that an attribute should
 not be used as a public API for the code, use the convention of naming
 the attribute with a single leading underscore. This is a string
 signal that the attribute is part of the implementation, not the
 interface. The reader is then on notice that they should not rely on
 that attribute; but they are not *prohibited* from using it if
 necessary to their ends.

But they will resent you just as much if you decide to rewrite
your module in such a way that the attribute is no longer present
or is used now in a slightly different way, so that it break code.

-- 
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Re: Why does python not have a mechanism for data hiding?

[Antoon Pardon]

On 2008-05-24, Sh4wn [EMAIL PROTECTED] wrote:
 Hi,

 first, python is one of my fav languages, and i'll definitely keep
 developing with it. But, there's 1 one thing what I -really- miss:
 data hiding. I know member vars are private when you prefix them with
 2 underscores, but I hate prefixing my vars, I'd rather add a keyword
 before it.

 Python advertises himself as a full OOP language, but why does it miss
 one of the basic principles of OOP? Will it ever be added to python?

 Thanks in advance,
 Lucas

If you really need it, you can do data hiding in python. It just
requires a bit more work.

- Hide.py -
class Rec(object):
 def __init__(__, **kwargs):
 for key,value in kwargs.items():
 setattr(__, key, value)

 def __getitem__(self, key):
 return getattr(self, key)

 def __setitem__ (self, key, val):
 setattr(self, key, val)

class Foo(object):

  def __init__(self):

hidden = Rec(x=0, y=0)

def SetX(val):
  hidden.x = val

def SetY(val):
  hidden.y = val

def GetX():
  return hidden.x

def GetY():
  return hidden.y

self.SetX = SetX
self.SetY = SetY
self.GetX = GetX
self.GetY = GetY

--
$ python
Python 2.5.2 (r252:60911, Apr 17 2008, 13:15:05) 
[GCC 4.2.3 (Debian 4.2.3-3)] on linux2
Type help, copyright, credits or license for more information.
 From Hide import Foo
 var = Foo()
 var.GetX()
0
 var.SetX(5)
 var.GetX()
5
 var.x
Traceback (most recent call last):
  File stdin, line 1, in module
AttributeError: 'Foo' object has no attribute 'x'
 var.hidden.x
Traceback (most recent call last):
  File stdin, line 1, in module
AttributeError: 'Foo' object has no attribute 'hidden'

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Re: Why does python not have a mechanism for data hiding?

[Duncan Booth]

Antoon Pardon [EMAIL PROTECTED] wrote:

 If you really need it, you can do data hiding in python. It just
 requires a bit more work.
snip
 --- $ python
 Python 2.5.2 (r252:60911, Apr 17 2008, 13:15:05) 
 [GCC 4.2.3 (Debian 4.2.3-3)] on linux2
 Type help, copyright, credits or license for more information.
 From Hide import Foo
 var = Foo()
 var.GetX()
 0
 var.SetX(5)
 var.GetX()
 5
 var.x
 Traceback (most recent call last):
   File stdin, line 1, in module
 AttributeError: 'Foo' object has no attribute 'x'
 var.hidden.x
 Traceback (most recent call last):
   File stdin, line 1, in module
 AttributeError: 'Foo' object has no attribute 'hidden'


That sort of hiding isn't any more secure than the 'hiding' you get in C++.
 
 var.GetX.func_closure[0].cell_contents.x
5

All you've done is force the user who wants to bypass it to use a longer 
expression, and if that's your criterion for 'hiding' then just use two 
leading underscores.

-- 
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Re: Why does python not have a mechanism for data hiding?

[Carl Banks]

On Jun 2, 5:38 am, Antoon Pardon [EMAIL PROTECTED] wrote:
 If you really need it, you can do data hiding in python. It just
 requires a bit more work.

 - Hide.py -
 class Rec(object):
  def __init__(__, **kwargs):
  for key,value in kwargs.items():
  setattr(__, key, value)

  def __getitem__(self, key):
  return getattr(self, key)

  def __setitem__ (self, key, val):
  setattr(self, key, val)

 class Foo(object):

   def __init__(self):

 hidden = Rec(x=0, y=0)

 def SetX(val):
   hidden.x = val

 def SetY(val):
   hidden.y = val

 def GetX():
   return hidden.x

 def GetY():
   return hidden.y

 self.SetX = SetX
 self.SetY = SetY
 self.GetX = GetX
 self.GetY = GetY

Red Herring.

1. This doesn't hide the variables; it just changes their spelling.
2. This also hides the variables from its own class.

In other words, it's a useless no-op.

In fact, I'd say this is even worse than useless.  Creating accessor
functions is a sort of blessing for external use.  Knowing that there
are accessor functions is likely to cause a user to show even less
restraint.


Carl Banks

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Re: Writing HTML

[Ken Starks]

[EMAIL PROTECTED] wrote:

I've searched the standard library docs, and, while there are a couple
options for *reading* HTML from Python, I didn't notice any for
*writing* it.  Does anyone have any recommendations (particularly ones
not listed on PyPI)?

Thanks


My approach is usually to write the data-load in XML rather than
directly in HTML, and then use XSLT to produce the (X)HTML.

You can do the whole of this, or just the second part, using
FourSuite.

If the XML, later, needs to be changed, you can use FourSuite
to drill down to somewhere using XPath and change that
particular part.

But none of this is really specific to Python, its the
XML skill-set you really need.

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Re: Writing HTML

[miller . paul . w]

On Jun 2, 6:11 am, Ken Starks [EMAIL PROTECTED] wrote:

 My approach is usually to write the data-load in XML rather than
 directly in HTML, and then use XSLT to produce the (X)HTML.

That's a good idea I hadn't considered.  Thanks!
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Shed my a light :)

[TheSaint]

Hi,
I using eval for quite strange reason, as long as I don't know a different
way to implement.

An example:

actions= ('print', 'sum', 'divide', 'myfunction')
parameters=(5, 'nothing',5.63, object)

for routines in actions:
 routines(parameters)

I'd like to note that actions are string or string expressions of the program
functions or python itself, so I've in my program something like:

for nn in actions:
   eval('cp.%s' %nn)

Where cp is an instance.

So I'm asking here whether exist a way that these string become functions
inside my program, without using eval()

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Re: Why does python not have a mechanism for data hiding?

[Antoon Pardon]

On 2008-06-02, Duncan Booth [EMAIL PROTECTED] wrote:
 Antoon Pardon [EMAIL PROTECTED] wrote:

 If you really need it, you can do data hiding in python. It just
 requires a bit more work.
snip
 --- $ python
 Python 2.5.2 (r252:60911, Apr 17 2008, 13:15:05) 
 [GCC 4.2.3 (Debian 4.2.3-3)] on linux2
 Type help, copyright, credits or license for more information.
 From Hide import Foo
 var = Foo()
 var.GetX()
 0
 var.SetX(5)
 var.GetX()
 5
 var.x
 Traceback (most recent call last):
   File stdin, line 1, in module
 AttributeError: 'Foo' object has no attribute 'x'
 var.hidden.x
 Traceback (most recent call last):
   File stdin, line 1, in module
 AttributeError: 'Foo' object has no attribute 'hidden'


 That sort of hiding isn't any more secure than the 'hiding' you get in C++.

So?

 var.GetX.func_closure[0].cell_contents.x
 5

 All you've done is force the user who wants to bypass it to use a longer 
 expression, and if that's your criterion for 'hiding' then just use two 
 leading underscores.

That you can find a lock pick to get at an object doesn't contradict
that the object is locked away.

I think the intention of not having these variables accesable to
the application programmer is much stronger expressed than with
two leading underscores.

Even if the current implementation of the language makes it
relatively easy to get at the information if you really want
to.

-- 
Antoon Pardon
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Re: Why does python not have a mechanism for data hiding?

[Antoon Pardon]

On 2008-06-02, Carl Banks [EMAIL PROTECTED] wrote:
 On Jun 2, 5:38 am, Antoon Pardon [EMAIL PROTECTED] wrote:
 If you really need it, you can do data hiding in python. It just
 requires a bit more work.

 - Hide.py -
 class Rec(object):
  def __init__(__, **kwargs):
  for key,value in kwargs.items():
  setattr(__, key, value)

  def __getitem__(self, key):
  return getattr(self, key)

  def __setitem__ (self, key, val):
  setattr(self, key, val)

 class Foo(object):

   def __init__(self):

 hidden = Rec(x=0, y=0)

 def SetX(val):
   hidden.x = val

 def SetY(val):
   hidden.y = val

 def GetX():
   return hidden.x

 def GetY():
   return hidden.y

 self.SetX = SetX
 self.SetY = SetY
 self.GetX = GetX
 self.GetY = GetY

 Red Herring.

 1. This doesn't hide the variables; it just changes their spelling.
 2. This also hides the variables from its own class.

 In other words, it's a useless no-op.

 In fact, I'd say this is even worse than useless.  Creating accessor
 functions is a sort of blessing for external use.  Knowing that there
 are accessor functions is likely to cause a user to show even less
 restraint.

I think you completed missed the point.

This is just a proof of concept thing. In a real example there would
of course no Set en Get methods but just methods that in the course
of their execution would access or update the hidden attributes 

-- 
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Re: Shed my a light :)

[Chris]

On Jun 2, 12:35 pm, TheSaint [EMAIL PROTECTED] wrote:
 Hi,
 I using eval for quite strange reason, as long as I don't know a different
 way to implement.

 An example:

 actions= ('print', 'sum', 'divide', 'myfunction')
 parameters=(5, 'nothing',5.63, object)

 for routines in actions:
      routines(parameters)

 I'd like to note that actions are string or string expressions of the program
 functions or python itself, so I've in my program something like:

 for nn in actions:
        eval('cp.%s' %nn)

 Where cp is an instance.

 So I'm asking here whether exist a way that these string become functions
 inside my program, without using eval()

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help(getattr)
Help on built-in function getattr in module __builtin__:

getattr(...)
getattr(object, name[, default]) - value

Get a named attribute from an object; getattr(x, 'y') is
equivalent to x.y.
When a default argument is given, it is returned when the
attribute doesn't
exist; without it, an exception is raised in that case.


for nn in actions:
func = getattr(cp, nn)
if callable(func):
func(parameters)

or alternatively

for nn in actions:
getattr(cp, nn)(parameters)

Hope that helps.
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Re: Shed my a light :)

[Duncan Booth]

TheSaint [EMAIL PROTECTED] wrote:

 actions= ('print', 'sum', 'divide', 'myfunction')
 parameters=(5, 'nothing',5.63, object)
 
 for routines in actions:
  routines(parameters)
 
 I'd like to note that actions are string or string expressions of the
 program functions or python itself, so I've in my program something
 like: 
 
 for nn in actions:
eval('cp.%s' %nn)
 
 Where cp is an instance.
 
 So I'm asking here whether exist a way that these string become
 functions inside my program, without using eval()

eval('cp.%s' %nn) is more cleanly done as: getattr(cp, nn)

In the more general case, you could just use the functions/methods directly 
instead of using their names:

actions = (cp.Print, cp.sum, cp.divide, cp.myfunction)
for nn in actions:
nn(parameters)


-- 
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mocking a logging object

[Peter Bengtsson]

In my unittest I want to override the logger of a working module so
that it puts all logging messages in /tmp/test.log instead so that in
my unittest I can inspect that it logs things correctly. Hopefully
this pseudo code will explain my problem::

 import logging, os
 logging.basicConfig(filename='/tmp/real.log', level=logging.INFO)
 logger = logging.getLogger('Real')
 logger.info('Real stuff')
 os.path.isfile('/tmp/real.log')
True
 # do the monkey patching like the unit test does
 logging.basicConfig(filename='/tmp/test.log', level=logging.INFO)
 logger = logging.getLogger('Test')
 logger.info('Test stuff')
 os.path.isfile('/tmp/test.log')
False
 open('/tmp/real.log').read()
'INFO:Real:Real stuff\nINFO:Test:Test stuff\n'

How can I change what file the logger should write to?
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Re: mocking a logging object

[Diez B. Roggisch]

Peter Bengtsson wrote:

 In my unittest I want to override the logger of a working module so
 that it puts all logging messages in /tmp/test.log instead so that in
 my unittest I can inspect that it logs things correctly. Hopefully
 this pseudo code will explain my problem::
 
 import logging, os
 logging.basicConfig(filename='/tmp/real.log', level=logging.INFO)
 logger = logging.getLogger('Real')
 logger.info('Real stuff')
 os.path.isfile('/tmp/real.log')
 True
 # do the monkey patching like the unit test does
 logging.basicConfig(filename='/tmp/test.log', level=logging.INFO)
 logger = logging.getLogger('Test')
 logger.info('Test stuff')
 os.path.isfile('/tmp/test.log')
 False
 open('/tmp/real.log').read()
 'INFO:Real:Real stuff\nINFO:Test:Test stuff\n'
 
 How can I change what file the logger should write to?

You should simply attach a new handler to the logger in question that logs
the data into a stream/StringIO-object for later retrieval. Then remove
that handler after the test.

Diez
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Re: Why does python not have a mechanism for data hiding?

[Carl Banks]

On Jun 2, 6:40 am, Antoon Pardon [EMAIL PROTECTED] wrote:
 On 2008-06-02, Carl Banks [EMAIL PROTECTED] wrote:



  On Jun 2, 5:38 am, Antoon Pardon [EMAIL PROTECTED] wrote:
  If you really need it, you can do data hiding in python. It just
  requires a bit more work.

  - Hide.py -
  class Rec(object):
   def __init__(__, **kwargs):
   for key,value in kwargs.items():
   setattr(__, key, value)

   def __getitem__(self, key):
   return getattr(self, key)

   def __setitem__ (self, key, val):
   setattr(self, key, val)

  class Foo(object):

def __init__(self):

  hidden = Rec(x=0, y=0)

  def SetX(val):
hidden.x = val

  def SetY(val):
hidden.y = val

  def GetX():
return hidden.x

  def GetY():
return hidden.y

  self.SetX = SetX
  self.SetY = SetY
  self.GetX = GetX
  self.GetY = GetY

  Red Herring.

  1. This doesn't hide the variables; it just changes their spelling.
  2. This also hides the variables from its own class.

  In other words, it's a useless no-op.

  In fact, I'd say this is even worse than useless.  Creating accessor
  functions is a sort of blessing for external use.  Knowing that there
  are accessor functions is likely to cause a user to show even less
  restraint.

 I think you completed missed the point.

I'm not sure I missed the point so much as I failed to read your mind.


 This is just a proof of concept thing. In a real example there would
 of course no Set en Get methods but just methods that in the course
 of their execution would access or update the hidden attributes

Fair enough, but I don't see anything in your example that suggests a
way to discriminate between access from within the class and access
from outside the class, which is the crucial aspect of data hiding.


Carl Banks


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GOZERBOT 0.8.1.0 released

[Bart Thate]

0.8.1.0 is here and can be downloaded from http://gozerbot.org

new features:

* ssl connections are now supported
* third party software included into gozerbot:
  o feedparser (used by RSS) .. makes atom feeds possible
  o simplejson (used by COLLECTIVE)
  o BeautifulSoup (used to parse webpages)
* renewed RSS plugin
* renewed collective plugin
* renewed webserver plugin .. new webserver API
* tcp.py notification plugin as well as a totcp.py client program

the following plugins were removed from the main distribition:

* autovoice
* away
* convert
* country
* event
* grab
* jcoll
* probe

if you are using one of these plugins use install-plug plugin to
install them from the plugin server.

any problems with the bot can be reported on #dunkbots on IRCnet or
email [EMAIL PROTECTED]

debian package and freebsd port will follow

have fun ;]

about gozerbot:

Requirements

* a shell
* python 2.4 or higher
* if you want to remotely install plugins: the gnupg module
* if you want mysql support: the py-MySQLdb module
* if you want jabber support: the xmpppy module

Why gozerbot?

* provide both IRC and Jabber support
* user management by userhost .. bot will not respond if it
doesn't know you
* fleet .. use more than one bot in a program (list of bots)
* use the bot through dcc chat
* fetch rss feeds
* remember items
* relaying between bots
* program your own plugins
* run the builtin webserver
* query other bots webserver via irc
* serve as a udp - irc or jabber notification bot
* mysql and sqlite support
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Re: Why does python not have a mechanism for data hiding?

[Carl Banks]

On Jun 2, 8:14 am, Carl Banks [EMAIL PROTECTED] wrote:
 Fair enough, but I don't see anything in your example that suggests a
 way to discriminate between access from within the class and access
 from outside the class, which is the crucial aspect of data hiding.


And, if you want an example of something that does that, how about
this metaclass.  It creates a class that checks the stack frame to see
if the caller was defined in the same class.

Issues:
Classes are prevented from defining their own __setattr__ and
__getattribute__.
Classes and subclasses should not use the same names for their private
variables.
Private attribute access is pretty slow, but that's obvious.
Pretty easy to thwart.


#--
import sys
import itertools

class PrivateAccessError(Exception):
pass

class PrivateDataMetaclass(type):
def __new__(metacls,name,bases,dct):

function = type(lambda x:x)

privates = set(dct.get('__private__',()))

codes = set()
for val in dct.itervalues():
if isinstance(val,function):
codes.add(val.func_code)

getframe = sys._getframe
count = itertools.count

def __getattribute__(self,attr):
if attr in privates:
for i in count(1):
code = getframe(i).f_code
if code in codes:
break
if code.co_name != '__getattribute__':
raise PrivateAccessError(
attribute '%s' is private % attr)
return super(cls,self).__getattribute__(attr)

def __setattr__(self,attr,val):
if attr in privates:
for i in count(1):
code = getframe(i).f_code
if code in codes:
break
if code.co_name != '__setattr__':
raise PrivateAccessError(
attribute '%s' is private % attr)
return super(cls,self).__setattr__(attr,val)

dct['__getattribute__'] = __getattribute__
dct['__setattr__'] = __setattr__

cls = type.__new__(metacls,name,bases,dct)

return cls

#--
import traceback

class A(object):
__metaclass__ = PrivateDataMetaclass
__private__ = ['internal']

def __init__(self,n):
self.internal = n

def inc(self):
self.internal += 1

def res(self):
return self.internal


class B(A):
__private__ = ['internal2']

def __init__(self,n,m):
super(B,self).__init__(n)
self.internal2 = m

def inc(self):
super(B,self).inc()
self.internal2 += 2

def res(self):
return self.internal2 + super(B,self).res()

def bad(self):
return self.internal2 + self.internal


a = A(1)
a.inc()

print Should print 2:
print a.res()
print

print Should raise PrivateAccessError:
try:
print a.internal
except PrivateAccessError:
traceback.print_exc()
print

b = B(1,1)
b.inc()

print Should print 5:
print b.res()
print

print Should raise PrivateAccessError:
try:
print b.internal2
except PrivateAccessError:
traceback.print_exc()
print

print Should raise PrivateAccessError:
try:
print b.bad()
except PrivateAccessError:
traceback.print_exc()
print
#--



Carl Banks
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Re: Why does python not have a mechanism for data hiding?

[Antoon Pardon]

On 2008-06-02, Carl Banks [EMAIL PROTECTED] wrote:
 On Jun 2, 6:40 am, Antoon Pardon [EMAIL PROTECTED] wrote:
 On 2008-06-02, Carl Banks [EMAIL PROTECTED] wrote:



  On Jun 2, 5:38 am, Antoon Pardon [EMAIL PROTECTED] wrote:
  If you really need it, you can do data hiding in python. It just
  requires a bit more work.

  - Hide.py -
  class Rec(object):
   def __init__(__, **kwargs):
   for key,value in kwargs.items():
   setattr(__, key, value)

   def __getitem__(self, key):
   return getattr(self, key)

   def __setitem__ (self, key, val):
   setattr(self, key, val)

  class Foo(object):

def __init__(self):

  hidden = Rec(x=0, y=0)

  def SetX(val):
hidden.x = val

  def SetY(val):
hidden.y = val

  def GetX():
return hidden.x

  def GetY():
return hidden.y

  self.SetX = SetX
  self.SetY = SetY
  self.GetX = GetX
  self.GetY = GetY

  In other words, it's a useless no-op.

  In fact, I'd say this is even worse than useless.  Creating accessor
  functions is a sort of blessing for external use.  Knowing that there
  are accessor functions is likely to cause a user to show even less
  restraint.

 I think you completed missed the point.

 I'm not sure I missed the point so much as I failed to read your mind.

Fine with me, it is just the other side of the coin.

 This is just a proof of concept thing. In a real example there would
 of course no Set en Get methods but just methods that in the course
 of their execution would access or update the hidden attributes

 Fair enough, but I don't see anything in your example that suggests a
 way to discriminate between access from within the class and access
 from outside the class, which is the crucial aspect of data hiding.

The fact is that hidden and its attributes are not accessible from
outside the instance. They are only accessible to the local functions
of __init__. By binding those local functions as atributes to the
instance, hidden can be modified by what for all practical purposes
looks like a method call, but really is a closure call.

-- 
Antoon Pardon
--
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Re: a question about the #prefix of sys.argv

[Fossil Pan]

On Jun 2, 8:50 am, Aldarion [EMAIL PROTECTED] wrote:
 On 6月2日, 上午8时05分, Peter Otten [EMAIL PROTECTED] wrote:

  Aldarion wrote:
   for the little script
   #egg.py
   import sys
   for k,v in enumerate(sys.argv):
   print k,v

   it ignores  the part after # on linux
   below is the running output on windows and linux. no clue here.

  This has nothing to do with python, it's the shell that treats the # and
  everything that follows as a comment.

  $ ./listargs.py alpha #beta
  0 ./listargs.py
  1 alpha

  But you can escape it:

  $ ./listargs.py alpha \#beta
  0 ./listargs.py
  1 alpha
  2 #beta

  $ ./listargs.py alpha '#beta'
  0 ./listargs.py
  1 alpha
  2 #beta

  Peter

 thanks everyone for the quickly reply, i see now.

Thank you Aldarion for your post.
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Re: Why does python not have a mechanism for data hiding?

[Carl Banks]

On Jun 2, 9:07 am, Antoon Pardon [EMAIL PROTECTED] wrote:
 On 2008-06-02, Carl Banks [EMAIL PROTECTED] wrote:



  On Jun 2, 6:40 am, Antoon Pardon [EMAIL PROTECTED] wrote:
  On 2008-06-02, Carl Banks [EMAIL PROTECTED] wrote:

   On Jun 2, 5:38 am, Antoon Pardon [EMAIL PROTECTED] wrote:
   If you really need it, you can do data hiding in python. It just
   requires a bit more work.

   - Hide.py -
   class Rec(object):
def __init__(__, **kwargs):
for key,value in kwargs.items():
setattr(__, key, value)

def __getitem__(self, key):
return getattr(self, key)

def __setitem__ (self, key, val):
setattr(self, key, val)

   class Foo(object):

 def __init__(self):

   hidden = Rec(x=0, y=0)

   def SetX(val):
 hidden.x = val

   def SetY(val):
 hidden.y = val

   def GetX():
 return hidden.x

   def GetY():
 return hidden.y

   self.SetX = SetX
   self.SetY = SetY
   self.GetX = GetX
   self.GetY = GetY

   In other words, it's a useless no-op.

   In fact, I'd say this is even worse than useless.  Creating accessor
   functions is a sort of blessing for external use.  Knowing that there
   are accessor functions is likely to cause a user to show even less
   restraint.

  I think you completed missed the point.

  I'm not sure I missed the point so much as I failed to read your mind.

 Fine with me, it is just the other side of the coin.

  This is just a proof of concept thing. In a real example there would
  of course no Set en Get methods but just methods that in the course
  of their execution would access or update the hidden attributes

  Fair enough, but I don't see anything in your example that suggests a
  way to discriminate between access from within the class and access
  from outside the class, which is the crucial aspect of data hiding.

 The fact is that hidden and its attributes are not accessible from
 outside the instance. They are only accessible to the local functions
 of __init__. By binding those local functions as atributes to the
 instance, hidden can be modified by what for all practical purposes
 looks like a method call, but really is a closure call.

You haven't hidden the data at all, all you've done is to change the
means of accessing it.  What difference does it make whether I write
foo.getX() or foo.x?  Everyone in the world still has full access to
the data.

You are not realizing that only useful(**) thing about data hiding is
that some code has access to the data, other code does not.  If you
hide data equally from everyone it's just a useless spelling change.


** - Usefulness is questionable in most cases, but we assume it is
here for the sake of argument.


Carl Banks
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Re: Shed my a light :)

[Paul Melis]

TheSaint wrote:

On 19:06, lunedì 02 giugno 2008 Chris wrote:



actions= ('print', 'sum', 'divide', 'myfunction')
parameters=(5, 'nothing',5.63, object)



8 8


getattr(...)
   getattr(object, name[, default]) - value


8 8


for nn in actions:
   func = getattr(cp, nn)
   if callable(func):
   func(parameters)


I got the point of Duncan and I should remain on evail() because the
evaluation is made on a construct of string expression, which give me the
final name of the function I want to call.


Why do you still need eval? Can't you just construct the string 
describing the function to call and then use getattr() to get the actual 
function object to call?



I've tried on Pyshell and clearly said the object str is not callable.


Well no, but I don't think anyone suggested that it would be.
The name of a function to call and the function itself are different 
things. getattr() helps you to get from the first to the latter.



Some of those string are functions inside the module, so I was expecting a
sequence of calls according the passed in functions names, but they *must*
be processed as a python statements ;(


This doesn't exactly make sense, as what you want isn't really clear...

Paul
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Re: Why does python not have a mechanism for data hiding?

[Antoon Pardon]

On 2008-06-02, Carl Banks [EMAIL PROTECTED] wrote:
 On Jun 2, 9:07 am, Antoon Pardon [EMAIL PROTECTED] wrote:
 On 2008-06-02, Carl Banks [EMAIL PROTECTED] wrote:



  On Jun 2, 6:40 am, Antoon Pardon [EMAIL PROTECTED] wrote:
  On 2008-06-02, Carl Banks [EMAIL PROTECTED] wrote:

   On Jun 2, 5:38 am, Antoon Pardon [EMAIL PROTECTED] wrote:
   If you really need it, you can do data hiding in python. It just
   requires a bit more work.

   - Hide.py -
   class Rec(object):
def __init__(__, **kwargs):
for key,value in kwargs.items():
setattr(__, key, value)

def __getitem__(self, key):
return getattr(self, key)

def __setitem__ (self, key, val):
setattr(self, key, val)

   class Foo(object):

 def __init__(self):

   hidden = Rec(x=0, y=0)

   def SetX(val):
 hidden.x = val

   def SetY(val):
 hidden.y = val

   def GetX():
 return hidden.x

   def GetY():
 return hidden.y

   self.SetX = SetX
   self.SetY = SetY
   self.GetX = GetX
   self.GetY = GetY

   In other words, it's a useless no-op.

   In fact, I'd say this is even worse than useless.  Creating accessor
   functions is a sort of blessing for external use.  Knowing that there
   are accessor functions is likely to cause a user to show even less
   restraint.

  I think you completed missed the point.

  I'm not sure I missed the point so much as I failed to read your mind.

 Fine with me, it is just the other side of the coin.

  This is just a proof of concept thing. In a real example there would
  of course no Set en Get methods but just methods that in the course
  of their execution would access or update the hidden attributes

  Fair enough, but I don't see anything in your example that suggests a
  way to discriminate between access from within the class and access
  from outside the class, which is the crucial aspect of data hiding.

 The fact is that hidden and its attributes are not accessible from
 outside the instance. They are only accessible to the local functions
 of __init__. By binding those local functions as atributes to the
 instance, hidden can be modified by what for all practical purposes
 looks like a method call, but really is a closure call.

 You haven't hidden the data at all, all you've done is to change the
 means of accessing it.  What difference does it make whether I write
 foo.getX() or foo.x?  Everyone in the world still has full access to
 the data.

Can't you look beyond the specific example? The GetX is just an example.
Any local function of __init__ has access to hidden and its attributes
and could manipulate them, even if the class wouldn't define getters
and setters.


 You are not realizing that only useful(**) thing about data hiding is
 that some code has access to the data, other code does not.  If you
 hide data equally from everyone it's just a useless spelling change.

I already explained this. The code is a proof of concept. I agree that
the example itself doesn't do anything usefull, that doesn't mean that
the concept it is trying to illustrate is useless too.


Your metaclass can be used to make attributes private. Your metaclass
doesn't stop doing that because someone makes a class with a getter
and a setter for those private attributes. The same goes for my example.
The closure makes a variable inaccessable to the outside. That doesn't
change because I defined a getter and a setter for that closure
variable.

-- 
Antoon Pardon
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Re: mocking a logging object

[Peter Bengtsson]

On Jun 2, 12:34 pm, Diez B. Roggisch [EMAIL PROTECTED] wrote:
 Peter Bengtsson wrote:
  In my unittest I want to override the logger of a working module so
  that it puts all logging messages in /tmp/test.log instead so that in
  my unittest I can inspect that it logs things correctly. Hopefully
  this pseudo code will explain my problem::

  import logging, os
  logging.basicConfig(filename='/tmp/real.log', level=logging.INFO)
  logger = logging.getLogger('Real')
  logger.info('Real stuff')
  os.path.isfile('/tmp/real.log')
  True
  # do the monkey patching like the unit test does
  logging.basicConfig(filename='/tmp/test.log', level=logging.INFO)
  logger = logging.getLogger('Test')
  logger.info('Test stuff')
  os.path.isfile('/tmp/test.log')
  False
  open('/tmp/real.log').read()
  'INFO:Real:Real stuff\nINFO:Test:Test stuff\n'

  How can I change what file the logger should write to?

 You should simply attach a new handler to the logger in question that logs
 the data into a stream/StringIO-object for later retrieval. Then remove
 that handler after the test.

 Diez

Thanks! I'll try that.
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Re: parse dates

[Eddie Corns]

brechmos [EMAIL PROTECTED] writes:

Hi,

I have been using PHP the last while and in particular strtotime.
What I want to replicate is finding the second or fourth Monday of the
next month.  In PHP with strtotime it is easy (strtotime(second
Monday, strtotime(next month), but I can't find an easy way to do
it in Python.  I have seen DateUtil, but it seems to be able to do
only the simpler parsing (could be wrong).

Any other ideas?

http://code-bear.com/code/parsedatetime/

 import parsedatetime.parsedatetime as pdt
 p = pdt.Calendar()
 p.parse('next month')
((2008, 7, 1, 9, 0, 0, 1, 183, -1), 1)

Eddie
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Re: ValueError: unknown locale: UTF-8

[mr]

On Jun 1, 8:43 pm, Martin v. Löwis [EMAIL PROTECTED] wrote:
  ValueError: unknown locale: UTF-8

  This is on open bug or is there more to it?

 Do you have an environment variable set who is named
 either LANG or starts with LC_?

Actually, yes:

LC_CTYPE=UTF-8

where is it coming from? This is basically on a clean new machine...
who might be setting it? It is coming from a program elsewhere on the
system? How should python code deal with this?

Thanks! mario
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Greetings, fellow Pythonistas!

[The Pythonista]

Hello, all!

This post is to announce a new Python-oriented blog.  See my .sig for the 
URL.

I also have a question: is there any official method for getting listed 
on Planet Python?

Thanks!

A fellow Pythonista

-- 
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http://pythonista.wordpress.com
** Posted from http://www.teranews.com **
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Re: Shed my a light :)

[TheSaint]

On 19:06, lunedì 02 giugno 2008 Chris wrote:

 actions= ('print', 'sum', 'divide', 'myfunction')
 parameters=(5, 'nothing',5.63, object)

8 8
 getattr(...)
 getattr(object, name[, default]) - value
8 8
 for nn in actions:
 func = getattr(cp, nn)
 if callable(func):
 func(parameters)
I got the point of Duncan and I should remain on evail() because the
evaluation is made on a construct of string expression, which give me the
final name of the function I want to call.
I've tried on Pyshell and clearly said the object str is not callable.

Some of those string are functions inside the module, so I was expecting a
sequence of calls according the passed in functions names, but they *must*
be processed as a python statements ;(

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Re: printf in python

[gianluca]

On 2 Giu, 10:08, Hrvoje Niksic [EMAIL PROTECTED] wrote:
 gianluca [EMAIL PROTECTED] writes:
  Hy, I've a problem with may python library generated with swig from C
  code. I works and I can access all function but a  simèple function
  that print a string don't work's.
  The function is like this:
  int PrintTEST()
  {
   printf(TEST );
   return 1;
  }

 Finish the printed string with a newline, or call fflush(stdout).  By
 default stdout is line-buffered when connected to interactive displays.

Exuse me!
How could use it?. I've tried with '\n'  without result.

Thanks

Gianluca
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Re: ctypes, function pointers and a lot of trouble

[Matt]

Hi,

okay, thanks now my DLL function seems to accept the functions given, 
but instead of running my program keeps crashing (with windows address 
violation errors). I did some further investigations on that and figured 
out that the contextH variable is not just an identifier as I thought, 
but a quite complicated datastreamhandler.


Now to get it to work I additionally need to implement the following c 
Structures:


--CODE-

/* The internal data structure object of a stream */
typedefstructtagMemStreamData
{
cdCharmode;
cdInt32lPos;
cdUInt32dwVisibleSize;
cdUInt32dwBufferSize;
cdChar*cpBuffer;
}MemStreamData;

typedefstructtagFilStreamData
{
cdCharszFileName[MAX_PATH];
HANDLEhFile;
}FilStreamData;

--\CODE

This function just creates the pStream filestream (which is what I have 
to do too)


--CODE-

BOOLCreateMyFilStream(cdStream*pStream,
cdChar*szFileName )
{
FilStreamData*pFilStrm;

/* The domain for data is secured. */
pFilStrm = new FilStreamData;
if( pFilStrm == NULL )
{
returnFALSE;
}

/* Data is changed the first stage. */
pFilStrm-hFile = INVALID_HANDLE_VALUE;
strcpy( pFilStrm-szFileName, szFileName );

pStream-contextH = (cdContext)pFilStrm;
pStream-close = _CloseMyFilStream;
pStream-open = _OpenMyFilStream;
pStream-read = _ReadMyFilStream;
pStream-seek = _SeekMyFilStream;
pStream-tell = _TellMyFilStream;
pStream-write = _WriteMyFilStream;

returnTRUE;
}


--\CODE



Now my solution is the following:


--CODE-

class MemStreamData(Structure):
_fields_ = [(mode, c_byte),
 (lPos, c_uint),
 (dwVisibleSize, c_uint),
 (dwBufferSize, c_uint),
 (cpBuffer, POINTER(c_char))]

class FilStreamData (Structure):
_fields_ = [(szFileName, c_char * 30),
 (hFile, c_uint)]


--\CODE

and the code to fill all that with the right data is the following:

--CODE-

datainfo = cdReleaseImageInfo()

databuf = c_char * 10
cbuffer=MemStreamData()
cbuffer.mode = c_byte(0)
cbuffer.lPos = c_uint(0)
cbuffer.dwVisibleSize = c_uint(10)
cbuffer.dwBufferSize = c_uint(10)

#this line does not work, wrong datatype!?
cbuffer.cpBuffer = POINTER(databuf)

cpointer = cast(cbuffer, POINTER(c_uint))
stream = cdStream()
stream.contextH=cpointer
stream.open = cstreamopen(pystreamopen)
stream.close = cstreamclose(pystreamclose)
stream.write = cstreamwrite(pystreamwrite)
stream.tell = cstreamtell(pystreamtell)
stream.read = cstreamread(pystreamread)



data = cdStgMedium()
data.Type = c_uint(1)
data.u.pStream = POINTER(cdStream)(stream)

--\CODE

Does anyone see where the errors are?

Best regards and thanks a lot,
Matt






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Re: php vs python

[Lou Pecora]

In article [EMAIL PROTECTED],
 Ethan Furman [EMAIL PROTECTED] wrote:

 Jerry Stuckle wrote:
 
  
   As I've said before - good programmers can write good code in any
   language.
  
 
 So... an eloquent speaker of English is also an eloquent speaker of 
 Spanish/French/German?

Oh, Bull.  Computer languages are so narrow they are more like dialects 
of a single language. If you know English you can learn to speak to a 
Brit, Scot, or Aussie.   That's more like it...if you really want to 
stretch the definition of a language.  And it is a stretch.  Anyone 
speak C?

Sheeze.

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Re: ThreadPoolingMixIn

[pavel . uvarov]

On May 31, 9:13 pm, Rhamphoryncus [EMAIL PROTECTED] wrote:
 On May 30, 2:40 pm, [EMAIL PROTECTED] wrote:

  Hi, everybody!

  I wrote a useful class ThreadPoolingMixIn which can be used to create
  fast thread-based servers. This mix-in works much faster than
  ThreadingMixIn because it doesn't create a new thread on each request.

 Do you have any benchmarks demonstrating the performance difference/


To benchmark this I used a simple tcp server which writes a small
(16k)
string to the client and closes the connection.

I started 100 remote clients and got 500 replies/s for ThreadingMixIn
and more than 1500 replies/s for ThreadPoolingMixIn. I tested it on
FreeBSD 6.2 amd64.

I'm very curious about the exactness of the number 500 for
ThreadingMixIn. It seems to be the same for various packet sizes.
I suspect there is some OS limit on thread creating rate.

Below I include a bugfixed ThreadPoolingMixIn and the benchmarking
utility. The utility can be used to start clients on localhost, though
the reply rate will be slower (around 1000 replies/s).

To start benchmarking server with localhost clients use:
python ./TestServer.py --server=threading --n-clients=100
or
python ./TestServer.py --server=threadpooling --n-clients=100


#--- ThreadPoolingMixIn.py
from __future__ import with_statement
from SocketServer import ThreadingMixIn
import threading
import Queue
class ThreadPoolingMixIn(ThreadingMixIn):
Mix-in class to handle requests in a thread pool.

The pool grows and thrinks depending on load.

For instance, a threadpooling TCP server class is created as
follows:

class ThreadPoolingUDPServer(ThreadPoolingMixIn, TCPServer): pass



__author__ = 'Pavel Uvarov [EMAIL PROTECTED]'

def init_thread_pool(self, min_workers = 5,
 max_workers = 100, min_spare_workers = 5):
Initialize thread pool.
self.q = Queue.Queue()
self.min_workers = min_workers
self.max_workers = max_workers
self.min_spare_workers = min_spare_workers
self.num_workers = 0
self.num_busy_workers = 0
self.workers_mutex = threading.Lock()
self.start_workers(self.min_workers)

def start_workers(self, n):
Start n workers.
for i in xrange(n):
t = threading.Thread(target = self.worker)
t.setDaemon(True)
t.start()

def worker(self):
A function of a working thread.

It gets a request from queue (blocking if there
are no requests) and processes it.

After processing it checks how many spare workers
are there now and if this value is greater than
self.min_spare_workers then the worker exits.
Otherwise it loops infinitely.


with self.workers_mutex:
self.num_workers += 1
while True:
(request, client_address) = self.q.get()
with self.workers_mutex:
self.num_busy_workers += 1
self.process_request_thread(request, client_address)
self.q.task_done()
with self.workers_mutex:
self.num_busy_workers -= 1
if (self.num_workers  self.min_workers and
self.num_workers - self.num_busy_workers 
self.min_spare_workers):
self.num_workers -= 1
return

def process_request(self, request, client_address):
Puts a request into queue.

If the queue size is too large, it adds extra worker.


self.q.put((request, client_address))
with self.workers_mutex:
if self.q.qsize()  3 and self.num_workers 
self.max_workers:
self.start_workers(1)

def join(self):
Wait for all busy threads
self.q.join()

#--- TestServer.py
from __future__ import with_statement
from SocketServer import *
import socket
import sys
import threading
import time
import os
from ThreadPoolingMixIn import *

class ThreadPoolingTCPServer(ThreadPoolingMixIn, TCPServer): pass

class TestServer(ThreadingTCPServer):

allow_reuse_address = True
request_queue_size = 128

def __init__(self, server_address, RequestHandlerClass,
 packet_size):
TCPServer.__init__(self, server_address, RequestHandlerClass)
self.packet_size = packet_size
self.sum_t = 0
self.total_num_requests = 0
self.num_requests = 0
self.t0 = time.time()
self.lock = threading.Lock()

def reset_stats(self):
with self.lock:
self.total_num_requests += self.num_requests
self.num_requests = 0
self.sum_t = 0
self.t0 = time.time()

def update_stats(self, t0, t1):
with self.lock:
self.num_requests += 1
self.sum_t += t1 - t0
n = self.num_requests
sum_t = self.sum_t
avg_t = sum_t / n
rate = n / (t1 - 

Re: ThreadPoolingMixIn

[pavel . uvarov]

On Jun 2, 7:09 pm, [EMAIL PROTECTED] wrote:
 On May 31, 9:13 pm, Rhamphoryncus [EMAIL PROTECTED] wrote:

  On May 30, 2:40 pm, [EMAIL PROTECTED] wrote:

   Hi, everybody!

   I wrote a useful class ThreadPoolingMixIn which can be used to create
   fast thread-based servers. This mix-in works much faster than
   ThreadingMixIn because it doesn't create a new thread on each request.

  Do you have any benchmarks demonstrating the performance difference/

 To benchmark this I used a simple tcp server which writes a small
 (16k)
 string to the client and closes the connection.

 I started 100 remote clients and got 500 replies/s for ThreadingMixIn
 and more than 1500 replies/s for ThreadPoolingMixIn. I tested it on
 FreeBSD 6.2 amd64.

 I'm very curious about the exactness of the number 500 for
 ThreadingMixIn. It seems to be the same for various packet sizes.
 I suspect there is some OS limit on thread creating rate.

 Below I include a bugfixed ThreadPoolingMixIn and the benchmarking
 utility. The utility can be used to start clients on localhost, though
 the reply rate will be slower (around 1000 replies/s).

 To start benchmarking server with localhost clients use:
 python ./TestServer.py --server=threading --n-clients=100
 or
 python ./TestServer.py --server=threadpooling --n-clients=100

I've just tested it on a linux box and got a 240 replies/s vs 2000
replies/s, that is 8x performance improvement.
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Re: ThreadPoolingMixIn

[Michael Ströder]

[EMAIL PROTECTED] wrote:

To benchmark this I used a simple tcp server which writes a small
(16k)
string to the client and closes the connection.


Just a general note: When benchmarking such a network service it would 
be valuable to see benchmark results for several data sizes. I'd expect 
better numbers for a ThreadPoolingMixIn when there are more requests 
with smaller data size.


Ciao, Michael.
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Re: mocking a logging object

[Peter Bengtsson]

On Jun 2, 12:34 pm, Diez B. Roggisch [EMAIL PROTECTED] wrote:
 Peter Bengtsson wrote:
  In my unittest I want to override the logger of a working module so
  that it puts all logging messages in /tmp/test.log instead so that in
  my unittest I can inspect that it logs things correctly. Hopefully
  this pseudo code will explain my problem::

  import logging, os
  logging.basicConfig(filename='/tmp/real.log', level=logging.INFO)
  logger = logging.getLogger('Real')
  logger.info('Real stuff')
  os.path.isfile('/tmp/real.log')
  True
  # do the monkey patching like the unit test does
  logging.basicConfig(filename='/tmp/test.log', level=logging.INFO)
  logger = logging.getLogger('Test')
  logger.info('Test stuff')
  os.path.isfile('/tmp/test.log')
  False
  open('/tmp/real.log').read()
  'INFO:Real:Real stuff\nINFO:Test:Test stuff\n'

  How can I change what file the logger should write to?

 You should simply attach a new handler to the logger in question that logs
 the data into a stream/StringIO-object for later retrieval. Then remove
 that handler after the test.

 Diez

Yes! That worked. Thank you.
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Re: Shed my a light :)

[TheSaint]

On 22:00, lunedì 02 giugno 2008 Paul Melis wrote:

 This doesn't exactly make sense, as what you want isn't really clear...
Sorry, I'm bad to express my toughts even I my nature language :)
I'll give a go to getattr() and see whether the results come in my taste :)

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Re: ThreadPoolingMixIn

[pavel . uvarov]

On Jun 2, 7:15 pm, Michael Ströder [EMAIL PROTECTED] wrote:
 [EMAIL PROTECTED] wrote:
  To benchmark this I used a simple tcp server which writes a small
  (16k)
  string to the client and closes the connection.

 Just a general note: When benchmarking such a network service it would
 be valuable to see benchmark results for several data sizes. I'd expect
 better numbers for a ThreadPoolingMixIn when there are more requests
 with smaller data size.

 Ciao, Michael.

Here are benchmarks for FreeBSD 6.2, amd64

packet_size x y
  0499.57   1114.54
   1024499.29   1130.02
   3072500.09   1119.14
   7168498.20   .76
  15360499.29   1086.73
  31744500.04   1036.46
  64512499.43939.60
 130048499.28737.44
 261120498.04499.03
 523264307.54312.04
1047552173.57185.32
2096128 93.61 94.39

x = ThreadingMixIn replies/s
y = ThreadPoolingMixIn replies/s
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[Re] Checking each item in m.group()?

[[EMAIL PROTECTED]]

Hello

I need to go through each line of a CSV file, and extract some fields
using a regex. Then, I need to check each retrieved field, and if it
looks like , turn this into NULL so that it's correct SQL.

I tried a few things, but still can't it working:

#Second field might be empty - 
#Col1,
#Col1,Col2
p = re.compile('^(.+?),(.*?)$')

for line in textlines:
m = p.search(line)
if m:
#Check each column : if '', then turn into NULL


for col in line:
if col == :
col = NULL



for col in m.group():
if col == :
col=NULL



for col in m.group(0):
if col == :
col=NULL



for i in range (0,len(line)):
if line[i] == :
line[i]=NULL



for i in range(1,len(m.group(0))):
if m.group(i) == :
m.group(i)=NULL


sql = INSERT INTO mytable (col1, col2) VALUES
('%s','%s') % (m.group(1),m.group(2))
print sql
f.close()


Does someone know the correct syntax?

Thank you.
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python blogs

[pythonblogs]

Hello!

It seems like Python blogs are gaining popularity. It seems to me that
they play a crucial role in promoting Python as a language.
Do you agree with that?

Just a few days ago I've finished setting up a dedicated Python
blogging environment at:
http://www.pythonblogs.com
Do you think it will be useful for Python community?
By the way, everyone is welcome to join.

Sincerely yours,
~pyblog
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Re: printf in python

[gianluca]

On 2 Giu, 17:54, Dennis Lee Bieber [EMAIL PROTECTED] wrote:
 On Mon, 2 Jun 2008 00:32:33 -0700 (PDT), gianluca [EMAIL PROTECTED]
 declaimed the following in comp.lang.python:

  Hy, I've a problem with may python library generated with swig from C
  code. I works and I can access all function but a  simèple function
  that print a string don't work's.
  The function is like this:
  int PrintTEST()
  {
   printf(TEST );
   return 1;
  }

  If I call the function (myDLL.PrintTEST() ) the function print only
  the returned value, not the string TEST. Could anybody help me?

 Are you running from a command shell?

 If you are testing from inside something like IDLE (or PythonWin, or
 pretty much any other GUI development system) you may not have a stdout
 for display by C code...

 The return value would be printed by the Python interpreter in
 interactive mode...
 --
 WulfraedDennis Lee Bieber   KD6MOG
 [EMAIL PROTECTED]  [EMAIL PROTECTED]
 HTTP://wlfraed.home.netcom.com/
 (Bestiaria Support Staff:   [EMAIL PROTECTED])
 HTTP://www.bestiaria.com/

Hy,
the problem exists both in command shell and in IDLE. The  value is
correct  returned in both envirnment.

gianluca
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Re: ValueError: unknown locale: UTF-8

[Martin v. Löwis]

 Actually, yes:
 
 LC_CTYPE=UTF-8
 
 where is it coming from? This is basically on a clean new machine...
 who might be setting it?

There are many possible places. grep in your Library, as a starting
point. As on Macintosh lists.

 It is coming from a program elsewhere on the
 system? How should python code deal with this?

Python should do what it does: just crash. This setting is not supported.

Regards,
Martin
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Re: Checking each item in m.group()?

[Matimus]

On Jun 2, 11:42 am, [EMAIL PROTECTED] Gilles@ wrote:
 Hello

 I need to go through each line of a CSV file, and extract some fields
 using a regex. Then, I need to check each retrieved field, and if it
 looks like , turn this into NULL so that it's correct SQL.

 I tried a few things, but still can't it working:
 
 #Second field might be empty - 
 #Col1,
 #Col1,Col2
 p = re.compile('^(.+?),(.*?)$')

 for line in textlines:
 m = p.search(line)
 if m:
 #Check each column : if '', then turn into NULL

 
 for col in line:
 if col == :
 col = NULL
 

 
 for col in m.group():
 if col == :
 col=NULL
 

 
 for col in m.group(0):
 if col == :
 col=NULL
 

 
 for i in range (0,len(line)):
 if line[i] == :
 line[i]=NULL
 

 
 for i in range(1,len(m.group(0))):
 if m.group(i) == :
 m.group(i)=NULL
 

 sql = INSERT INTO mytable (col1, col2) VALUES
 ('%s','%s') % (m.group(1),m.group(2))
 print sql
 f.close()
 

 Does someone know the correct syntax?

 Thank you.

I think you want to use 'groups' instead of 'group'.

Here is a brief example. Note that this code is very insecure and
susceptible to a SQL injection attack. Hopefully these csv files are
from a trusted source.

sql = INSERT INTO mytable (col1, col2) VALUES ('%s','%s')%tuple(
(c, NULL)[c == ''] for c in m.groups()
)

Also, check out the csv module for parsing your csv file.

Matt
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Re: Writing HTML

[Stefan Behnel]

Ken Starks wrote:
 [EMAIL PROTECTED] wrote:
 I've searched the standard library docs, and, while there are a couple
 options for *reading* HTML from Python, I didn't notice any for
 *writing* it.  Does anyone have any recommendations (particularly ones
 not listed on PyPI)?

 Thanks
 
 My approach is usually to write the data-load in XML rather than
 directly in HTML, and then use XSLT to produce the (X)HTML.
 
 You can do the whole of this, or just the second part, using
 FourSuite.
 
 If the XML, later, needs to be changed, you can use FourSuite
 to drill down to somewhere using XPath and change that
 particular part.

Or lxml, for that purpose, which also is a lot nicer for generating XML and
HTML in the first place.

http://codespeak.net/lxml/

Stefan
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Re: ctypes, function pointers and a lot of trouble

[Nick Craig-Wood]

Matt [EMAIL PROTECTED] wrote:
  class MemStreamData(Structure):
   _fields_ = [(mode, c_byte),
(lPos, c_uint),
(dwVisibleSize, c_uint),
(dwBufferSize, c_uint),
(cpBuffer, POINTER(c_char))]
 
  class FilStreamData (Structure):
   _fields_ = [(szFileName, c_char * 30),
(hFile, c_uint)]
 
 
 
  and the code to fill all that with the right data is the following:
 
 
   datainfo = cdReleaseImageInfo()
 
   databuf = c_char * 10
   cbuffer=MemStreamData()
   cbuffer.mode = c_byte(0)
   cbuffer.lPos = c_uint(0)
   cbuffer.dwVisibleSize = c_uint(10)
   cbuffer.dwBufferSize = c_uint(10)
 
  #this line does not work, wrong datatype!?
   cbuffer.cpBuffer = POINTER(databuf)
[snip]
  Does anyone see where the errors are?

  databuf = c_char * 10

Is a type not an instance...

You need to instantiate it, eg

   from ctypes import *
   class MemStreamData(Structure):
  ... _fields_ = [(cpBuffer, POINTER(c_char))]
  ...
   cbuffer=MemStreamData()
   databuf = c_char * 10
   cbuffer.cpBuffer = POINTER(databuf)
  Traceback (most recent call last):
File stdin, line 1, in module
  TypeError: expected LP_c_char instance, got _ctypes.PointerType
   databuftype = c_char * 10
   databuf = databuftype()
   cbuffer.cpBuffer = databuf
   databuf
  __main__.c_char_Array_10 object at 0xb7d04dac

There is a shorthand for exactly this though as it is a common operation

   databuf = create_string_buffer(1000)
   cbuffer.cpBuffer = databuf
   databuf
  ctypes.c_char_Array_1000 object at 0xb7d129bc


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robotparser behavior on 403 (Forbidden) robot.txt files

[John Nagle]

  I just discovered that the robotparser module interprets
a 403 (Forbidden) status on a robots.txt file as meaning
all access disallowed. That's unexpected behavior.

  A major site (http://www.aplus.net/robot.txt;) has their
robots.txt file set up that way.

  There's no real robots.txt standard, unfortunately.
So it's not definitively a bug.

John Nagle
SiteTruth
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Re: Formatting Output

[Mensanator]

On Jun 2, 3:38 am, Chris [EMAIL PROTECTED] wrote:
 On Jun 2, 9:34 am, [EMAIL PROTECTED]

 [EMAIL PROTECTED] wrote:
  Hi,

  i am building a little script and i want to output a series of columns
  more or less like this:

  1  5  6
  2  2  8
  2  9  5

  The matter is that i don't know in advance how many columns there will
  be. By the way, each column will be actually FLOATs, not INTs. How can
  i do this ? Any help welcome. Regards,

  Victor

 import sys
 float_list = [1.0, 5.0, 6.0, 2.0, 2.0, 8.0, 2.0, 9.0, 5.0]
 num_columns = 3
 for i,item in enumerate(float_list):
     sys.stdout.write('%.4f\t' % item)
     if not (i+1) % num_columns:
         sys.stdout.write('\n')

 Problem with this approach is it doesn't cater for instances where you
 exceed the standard 80 characters for a terminal window.

That wouldn't be a problem if being re-directed to a file.

A bigger problem would be if his list were actually

[1.0,2.0,2.0,5.0,2.0,9.0,6.0,8.0,5.0]

but he still wanted it printed

1  5  6
2  2  8
2  9  5

as if he always wants 3 rows, but doesn't know how many columns
it will take. In which case, he could do something like this:

import sys
float_list = [1.0,2.0,2.0,5.0,2.0,9.0,6.0,8.0,5.0]
num_rows = 3
num_cols = divmod(len(float_list),num_rows)
for r in xrange(num_rows):
  for c in xrange(num_cols[0]):
sys.stdout.write('%.4f\t' % float_list[c*num_rows + r])
  if num_cols[1]0 and rnum_cols[1]:
sys.stdout.write('%.4f\t' % float_list[(c+1)*num_rows + r])
  sys.stdout.write('\n')

1.  5.  6.
2.  2.  8.
2.  9.  5.

And then changing list size would merely add more columns, so

[1.0,2.0,2.0,5.0,2.0,9.0,6.0,8.0,5.0,6.]

would print as

1.  5.  6.  6.
2.  2.  8.
2.  9.  5.


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Re: Formatting Output

[Doug Morse]

On Mon, 2 Jun 2008 12:42:12 -0700 (PDT), Mensanator [EMAIL PROTECTED] wrote:
  On Jun 2, 3:38 am, Chris [EMAIL PROTECTED] wrote:
  On Jun 2, 9:34 am, [EMAIL PROTECTED]
 
  [EMAIL PROTECTED] wrote:
   Hi,
 
   i am building a little script and i want to output a series of columns
   more or less like this:
 
   1  5  6
   2  2  8
   2  9  5
 ...

I have a related question:

Does Python have (or can emulate) the formatted output capability found in
Perl?

For example, all I have to do to get nicely formatted (i.e., aligned) output
is provide values for special STDOUT variables (i.e., STDOUT_TOP, STDOUT,
STDOUT_BOTTOM, etc.), exemplified by:


  format STDOUT_TOP =
  --
  ~
  .

  format STDOUT =
  @  @  @
  $res-{'full_name'},  $res-{'phone_1'}, $res-{'phone_1_type'}
  @  @ ~
  $res-{'address_1a'},$res-{'address_2a'}
  @  @ ~
  $res-{'address_1b'},$res-{'address_2b'}
  @  @ ~
  $res-{'address_1c'},$res-{'address_2c'}
  @  @ ~
  $city_1  $city_2
  @  @ ~
  $res-{'email_1'},   $res-{'email_2'}
  --
  ~
  .


Then, all I have to do is populate my $res object/hash as desired -- in this
example simple the results of a SQL query -- and lastly just call the write
function:

  write;

and Perl will produce very nicely formatted results.  This is useful not only
for producing human readable output, but also fixed-column-width data files,
etc.  I'd love to learn the Pythonistic way of doing the same thing.

Thanks!
Doug
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Re: ANN: equivalence 0.1

[Giuseppe Ottaviano]

On Jun 1, 2008, at 6:16 PM, George Sakkis wrote:


Equivalence is a class that can be used to maintain a partition of
objects into equivalence sets, making sure that the equivalence
properties (reflexivity, symmetry, transitivity) are preserved. Two
objects x and y are considered equivalent either implicitly (through a
key function) or explicitly by calling merge(x,y).


I think this library would be very useful, and I like the interface  
(in particular the idea of the projecting function), but I think the  
algorithm is less than optimal. It can show quadratic behavior in some  
cases:


$ python -m timeit -s 'import equivalence' -s 'eq =  
equivalence.Equivalence()' 'for i in xrange(1): eq.merge(i, i+1)'

10 loops, best of 3: 57.6 msec per loop

$ python -m timeit -s 'import equivalence' -s 'eq =  
equivalence.Equivalence()' 'for i in xrange(1): eq.merge(i+1, i)'

10 loops, best of 3: 2.59 sec per loop

Have you considered using the Union-Find algorithm, which would be  
(almost) linear in all cases?


-- Giuseppe
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Re: Python's doc problems: sort

[Martin Marcher]

Hi,

On Wed, Apr 30, 2008 at 4:48 AM, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
 For example, in last week, that page is fetched 550 times.
 The second most popular page, trails quite a distance. Here's the top

yup that was me, i have access to a couple of machines and wanted to
test some intercommunication, I faked most of the user agent strings
but still was locked out by popular pages. I then figured it would be
much better to fetch a useless page a couple of times.

Sorry for the lognoise...

/martin

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by doing so, you have violated my licence
and are required to urinate publicly. Thank you.
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Re: platypus in page header

[Mike Driscoll]

On Jun 2, 1:16 pm, Laszlo Nagy [EMAIL PROTECTED] wrote:
 Is it possible to use platypus in page header and footer? I need to
 create a document with long paragraphs but also I need to put tables and
 images in page header and multi line info in page footer with alignment etc.

 Thanks,

    Laszlo

From looking at the docs, it sounds like you could do that, if you
create your flowables correctly. You should probably ask over on the
reportlab user's list though. Those guys would almost certainly know:

http://two.pairlist.net/mailman/listinfo/reportlab-users

Mike
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Re: Why does python not have a mechanism for data hiding?

[Russ P.]

On Jun 2, 6:41 am, Carl Banks [EMAIL PROTECTED] wrote:

 You are not realizing that only useful(**) thing about data hiding is
 that some code has access to the data, other code does not.  If you
 hide data equally from everyone it's just a useless spelling change.

I think you're missing the point.

As I see it, the primary value of data hiding is that it provides
useful information on which data and methods are intended for the
client and which are intended for internal use. It's like putting a
front panel on a TV set with the main controls intended for the
viewer.

People seem to be preoccupied with whether or not the back panel of
the TV is locked, but that is not the main issue. Sure, you probably
want to make the back panel removable, but you don't want the viewer
opening it up to change the channel, and you certainly don't want to
put all the internal adjustments for factory technicians together with
the controls for the end user.

As far as I am concerned, the current Python method of using
underscores to distinguish between internal and external methods and
data is an ugly hack that goes completely against the elegance of the
language in other areas. It is like a TV set with no back cover and
the volume and channel controls intermingled with the factory
controls. The underscores are just an afterthought like a red dot or
something used to tell the TV viewer  what to fiddle with.

Python is a very nice language overall, but as far as I am concerned
the underscore convention is a blemish. I just wish people wouldn't
get so infatuated with the language that they cannot see the obvious
staring them in the face.
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Cast list of objects to list of strings

[bukzor]

I have this function:

def write_err(obj):
 from sys import stderr
 stderr.write(str(obj)+\n)

and I'd like to rewrite it to take a variable number of objects.
Something like this:

def write_err(*objs):
 from sys import stderr
 stderr.write( .join(objs)+\n)

but I lose the property that the function works on any object. What's
the simplest way to fix this? In essence, I need to cast a list of
objects to a list of strings. I'd like to do just str(objs) but that
(obviously) doesn't quite do what I need.

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Re: Writing HTML

[miller . paul . w]

On Jun 2, 3:19 pm, Stefan Behnel [EMAIL PROTECTED] wrote:

 Or lxml, for that purpose, which also is a lot nicer for generating XML and
 HTML in the first place.

 http://codespeak.net/lxml/

Awesome.  lxml looks like exactly what I'm after... and it's in the
Ubuntu repos. :-)  Thanks!
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Re: robotparser behavior on 403 (Forbidden) robot.txt files

[Martin v. Löwis]

   I just discovered that the robotparser module interprets
 a 403 (Forbidden) status on a robots.txt file as meaning
 all access disallowed. That's unexpected behavior.

That's specified in the norobots RFC:

http://www.robotstxt.org/norobots-rfc.txt

- On server response indicating access restrictions (HTTP Status
  Code 401 or 403) a robot should regard access to the site
  completely restricted.

So if a site returns 403, we should assume that it did so
deliberately, and doesn't want to be indexed.

  A major site (http://www.aplus.net/robot.txt;) has their
 robots.txt file set up that way.

You should try http://www.aplus.net/robots.txt; instead,
which can be accessed just fine.

Regards,
Martin
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Re: Cast list of objects to list of strings

[Larry Bates]

bukzor wrote:

I have this function:

def write_err(obj):
 from sys import stderr
 stderr.write(str(obj)+\n)

and I'd like to rewrite it to take a variable number of objects.
Something like this:

def write_err(*objs):
 from sys import stderr
 stderr.write( .join(objs)+\n)

but I lose the property that the function works on any object. What's
the simplest way to fix this? In essence, I need to cast a list of
objects to a list of strings. I'd like to do just str(objs) but that
(obviously) doesn't quite do what I need.


I think what you want is:

def write_err(*args):
from sys import stderr
stderr.write(\n.join([str(o) for o in args]))


but then I don't really understand why you would want such a function so I could 
be way wrong.


-Larry
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Re: [Re] Checking each item in m.group()?

[Peter Otten]

[EMAIL PROTECTED] wrote:

 I need to go through each line of a CSV file, and extract some fields
 using a regex. Then, I need to check each retrieved field, and if it
 looks like , turn this into NULL so that it's correct SQL.

You are taking the wrong approach here.

Don't build SQL statements as strings; you are enabling the next SQL
injection attack. Pass parameters using the DB API instead.

Don't use regular expressions to parse a CSV file. Python's csv module is
more likely to deal correctly with the quirks of that standard.

A self-contained example:


import csv

import sqlite3 as sqlite
from cStringIO import StringIO

def records(infile):
for row in csv.reader(infile):
# replace empty strings in the second column with None
# which translates to NULL in the database
yield row[0], row[1] or None

def main():
# create sample data; you may use a real file 
infile = StringIO(\
alpha,beta,gamma
zeta,,theta
)

# create the database
db = sqlite.connect(:memory:)
cursor = db.cursor()
cursor.execute(create table demo (first, second);)

# safely insert data
cursor.executemany(insert into demo values (?, ?);, records(infile))

# show contents
for row in cursor.execute(select first, second, second is NULL 
  from demo order by first, second;):
print row

if __name__ == __main__:
main()

Peter
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Re: python blogs

[miller . paul . w]

On Jun 2, 2:49 pm, [EMAIL PROTECTED] wrote:

 It seems like Python blogs are gaining popularity. It seems to me that
 they play a crucial role in promoting Python as a language.

Neat!  Do blogs on your site have to be about Python programming, or
can people blog about anything?
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Re: ThreadPoolingMixIn

[miller . paul . w]

On Jun 2, 12:41 pm, [EMAIL PROTECTED] wrote:
 On Jun 2, 7:15 pm, Michael Ströder [EMAIL PROTECTED] wrote:


 Here are benchmarks for FreeBSD 6.2, amd64

 packet_size         x         y
           0    499.57   1114.54
        1024    499.29   1130.02
        3072    500.09   1119.14
        7168    498.20   .76
       15360    499.29   1086.73
       31744    500.04   1036.46
       64512    499.43    939.60
      130048    499.28    737.44
      261120    498.04    499.03
      523264    307.54    312.04
     1047552    173.57    185.32
     2096128     93.61     94.39

 x = ThreadingMixIn replies/s
 y = ThreadPoolingMixIn replies/s

Well, I'd say you've got yourself a winner.  Performance (at least on
FreeBSD) seems as good or better for your ThreadPoolingMixin than
ThreadingMixin.  Is this with the default values of min=5 and max=5
worker threads?
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Re: Checking each item in m.group()?

[miller . paul . w]

On Jun 2, 5:06 pm, Peter Otten [EMAIL PROTECTED] wrote:

 You are taking the wrong approach here.

 Don't build SQL statements as strings; you are enabling the next SQL
 injection attack. Pass parameters using the DB API instead.

 Don't use regular expressions to parse a CSV file. Python's csv module is
 more likely to deal correctly with the quirks of that standard.


I'd like to second both these statements.  Regardless of whether these
CSV files are from a trusted source or not, it's a virtual truism of
programming that eventually, any application will be used in ways it
was not intended.  Since using a parameterized query is a simple way
to avoid a common security hole, even if such a thing could never be
exploited by the app in its current configuration, you should do
things the Right Way.  That way, even if your code is twisted to some
other use in the future, it's less likely to cause problems.
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Re: python blogs

[Mike Driscoll]

On Jun 2, 4:14 pm, [EMAIL PROTECTED] wrote:
 On Jun 2, 2:49 pm, [EMAIL PROTECTED] wrote:

  It seems like Python blogs are gaining popularity. It seems to me that
  they play a crucial role in promoting Python as a language.

 Neat!  Do blogs on your site have to be about Python programming, or
 can people blog about anything?


I personally like Doug Hellman's Python Module of the Week posts. The
people over at Planet TurboGears are usually interesting too.

http://blog.doughellmann.com/
http://planet.turbogears.org/

Other than those though, I haven't really seen much that's updated
regularly.

Mike
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Re: Formatting Output

[Chris]

On Jun 2, 9:43 pm, Doug Morse [EMAIL PROTECTED] wrote:
 On Mon, 2 Jun 2008 12:42:12 -0700 (PDT), Mensanator [EMAIL PROTECTED] wrote:
   On Jun 2, 3:38 am, Chris [EMAIL PROTECTED] wrote:
   On Jun 2, 9:34 am, [EMAIL PROTECTED]

   [EMAIL PROTECTED] wrote:
Hi,

i am building a little script and i want to output a series of columns
more or less like this:

1  5  6
2  2  8
2  9  5
  ...

 I have a related question:

 Does Python have (or can emulate) the formatted output capability found in
 Perl?

 For example, all I have to do to get nicely formatted (i.e., aligned) output
 is provide values for special STDOUT variables (i.e., STDOUT_TOP, STDOUT,
 STDOUT_BOTTOM, etc.), exemplified by:

   format STDOUT_TOP =
   
 --
   ~
   .

   format STDOUT =
   @  @  @
   $res-{'full_name'},  $res-{'phone_1'},         $res-{'phone_1_type'}
   @  @ ~
   $res-{'address_1a'},                $res-{'address_2a'}
   @  @ ~
   $res-{'address_1b'},                $res-{'address_2b'}
   @  @ ~
   $res-{'address_1c'},                $res-{'address_2c'}
   @  @ ~
   $city_1                              $city_2
   @  @ ~
   $res-{'email_1'},                   $res-{'email_2'}
   
 --
   ~
   .

 Then, all I have to do is populate my $res object/hash as desired -- in this
 example simple the results of a SQL query -- and lastly just call the write
 function:

   write;

 and Perl will produce very nicely formatted results.  This is useful not only
 for producing human readable output, but also fixed-column-width data files,
 etc.  I'd love to learn the Pythonistic way of doing the same thing.

 Thanks!
 Doug

Can't seem to do this with dictionaries but...

preformatted_string = 
%s %20s %20s
%s %30s
%s %30s


print preformatted_string % ('first name'[:20], 'contact num 1'[:20],
'contact num type'[:20], 'address line 1'[:30], 'address line
2'[:30]
'address line 3'[:30], 'address line 4'[:30])

You could do something like that.  the [:20] etc @ the end of the
inputs is ofc to trim the strings to a max length.  The string
formatter supports %number of characters to move to the rights so
you can use that for alignment.  It's a bit late so maybe I buggered
up when I tried to use dictionary assignment with it, but who knows :p
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Re: Formatting Output

[Chris]

On Jun 2, 11:34 pm, Chris [EMAIL PROTECTED] wrote:
 On Jun 2, 9:43 pm, Doug Morse [EMAIL PROTECTED] wrote:



  On Mon, 2 Jun 2008 12:42:12 -0700 (PDT), Mensanator [EMAIL PROTECTED] 
  wrote:
    On Jun 2, 3:38 am, Chris [EMAIL PROTECTED] wrote:
On Jun 2, 9:34 am, [EMAIL PROTECTED]

[EMAIL PROTECTED] wrote:
 Hi,

 i am building a little script and i want to output a series of columns
 more or less like this:

 1  5  6
 2  2  8
 2  9  5
   ...

  I have a related question:

  Does Python have (or can emulate) the formatted output capability found in
  Perl?

  For example, all I have to do to get nicely formatted (i.e., aligned) output
  is provide values for special STDOUT variables (i.e., STDOUT_TOP, STDOUT,
  STDOUT_BOTTOM, etc.), exemplified by:

    format STDOUT_TOP =
    
  --
    ~
    .

    format STDOUT =
    @  @  @
    $res-{'full_name'},  $res-{'phone_1'},         $res-{'phone_1_type'}
    @  @ ~
    $res-{'address_1a'},                $res-{'address_2a'}
    @  @ ~
    $res-{'address_1b'},                $res-{'address_2b'}
    @  @ ~
    $res-{'address_1c'},                $res-{'address_2c'}
    @  @ ~
    $city_1                              $city_2
    @  @ ~
    $res-{'email_1'},                   $res-{'email_2'}
    
  --
    ~
    .

  Then, all I have to do is populate my $res object/hash as desired -- in this
  example simple the results of a SQL query -- and lastly just call the 
  write
  function:

    write;

  and Perl will produce very nicely formatted results.  This is useful not 
  only
  for producing human readable output, but also fixed-column-width data files,
  etc.  I'd love to learn the Pythonistic way of doing the same thing.

  Thanks!
  Doug

 Can't seem to do this with dictionaries but...

 preformatted_string = 
 %s %20s %20s
 %s %30s
 %s %30s
 

 print preformatted_string % ('first name'[:20], 'contact num 1'[:20],
         'contact num type'[:20], 'address line 1'[:30], 'address line
 2'[:30]
         'address line 3'[:30], 'address line 4'[:30])

 You could do something like that.  the [:20] etc @ the end of the
 inputs is ofc to trim the strings to a max length.  The string
 formatter supports %number of characters to move to the rights so
 you can use that for alignment.  It's a bit late so maybe I buggered
 up when I tried to use dictionary assignment with it, but who knows :p

Actually just realised I had the number on the wrong side... :D

preformatted_string = 
%(first_name)s %(contact_num)20s %(contact_type)20s

print preformatted_string % {'first_name':'Chris',
'contact_num':'555-', 'contact_type':'Home'}
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Re: php vs python

[Patrick Mullen]

Yeah I would agree that a decent (a few steps below good in my book)
programmer should be able to have a decent handle on a new language, given
some acclimatization time of course.  The amount of time this period lasts
varies on the language said programmer is learning, as well as the languages
he knows.  If they are far different (say going from object oriented to
functional) it will take longer to learn.  But it's not to say that after
learning it, his code will be bad.  Maybe not as good as experts, but not
bad.

But I would say the jump from not bad code to good code; or the jump
from good code to great code are huge leaps.  And in a badly designed
language, it could be argued that even the best code is lacking.  To say
that language doesn't matter at all is extremely silly, otherwise we
wouldn't have 5 million languages.  Most languages are created, not just for
the fun of it, but to solve something lacking in what is available
elsewhere.  (OK, there are a lot of languages people have created just
because they are geeks, but most languages that people actually use are
purposeful).  Python was created to have something easier than perl and more
powerful than bash to write shell scripts with and automate system
administration tasks.  PHP was created to enhance html with a powerful
integrated server language that was easier than c but not alien to it.  It
was a replacement for cgi.

For me, php is far too flat, making it pretty tough to navigate and get a
handle on.  If you know what you want to do, it probably has something to
fit that task, but for exploring it's not fun.  I rather enjoy python, where
I can play around at the interpreter and try new things.  PHP also is not
very strict when it comes to types, even less strict than python, and in my
newbieness that has caused me loads of problems.  But I know people who
swear by PHP, and I admit it has been used for many great sites, so it can't
be that bad.

Still, outside of the web sphere, it is a bit odd to use PHP.  Not
necesarily bad, just a bit odd.  And there are situations that are a bit odd
for python also (sound editing,etc).
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Re: Cast list of objects to list of strings

[jay graves]

On Jun 2, 4:02 pm, Larry Bates [EMAIL PROTECTED] wrote:
 I think what you want is:
 def write_err(*args):
  from sys import stderr
  stderr.write(\n.join([str(o) for o in args]))

Slight nitpick.  If you are using version = 2.4 you could use a
generator expression instead of a list comprehension to avoid building
and throwing away a list.

\n.join(str(o) for o in args)

http://www.python.org/dev/peps/pep-0289/

Very unlikely to yield a material time difference in this case but
cleaner IMO.

...
Jay Graves
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Re: Merging ordered lists

[etal]

On Jun 1, 1:49 am, Peter Otten [EMAIL PROTECTED] wrote:
 Peter Otten wrote:
  #untested

 Already found two major blunders :(

 # still untested
 import difflib

 def _merge(a, b):
     sm = difflib.SequenceMatcher(None, a, b)
     for op, a1, a2, b1, b2 in sm.get_opcodes():
         if op == insert:
             yield b[b1:b2]
         elif op == replace:
             yield a[a1:a2]
             yield b[b1:b2]
         else: # delete, equal
             yield a[a1:a2]

 def merge(a, b):
     return sum(_merge(a, b), [])

 def merge_to_unique(sources):
     return unique(reduce(merge, sorted(sources, key=len, reverse=True)))


difflib.SequenceMatcher looks promising; I'll try it. Thanks!


 def unique(items):
     u = set(items)
     if len(u) == len(items):
         return items
     result = []
     for item in items:
         if item in u:
             result.append(item)
             u.remove(item)
     return result

You did right by preserving the original (non-alphabetical) ordering,
but I'm less enthusiastic about the shape of this function. My
original function used 7 lines of code, and only 1 for the unique()
step. This uses up to three container objects. Is it really an
improvement?

(Secret: the reference list (or, any of the sources) is unlikely to be
more than a few dozen elements long. The data set that puts
merge_to_unique through a workout will be a giant list of
comparatively short lists, so the unique() part just needs to be short
and conceptually clean, while merge() should attempt sane behavior for
large len(sources).)
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Re: Why does python not have a mechanism for data hiding?

[Diez B. Roggisch]

Well that's nice: you're accusing me of missing the point after having
quoted something I wrote as if it represented by own views, even
though I footnoted it and said I was only doing it for the sake of
argument.  Perhaps, outside this discussion, I am totally getting the
point.

I can't tell, though, because I read your post twice and I have no
idea what you consider the point to be.

Best as I can tell you are claiming that data hiding isn't important,
but then you go on to imply Python is blemished because it doesn't
hide data.  It really makes no sense: perhaps you can help us out by
giving us an example of something that illustrates what you're saying?


(FWIW, my actual view on the matter is I don't give a lick about data
hiding or marking internals.)


Do yourself a favor and google antoon's previous posts in this group. He 
sure is a clever guy  I wouldn't call him a troll - but a bit trollish..


Diez
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Re: Formatting Output

[Mensanator]

On Jun 2, 2:43 pm, Doug Morse [EMAIL PROTECTED] wrote:
 On Mon, 2 Jun 2008 12:42:12 -0700 (PDT), Mensanator [EMAIL PROTECTED] wrote:
   On Jun 2, 3:38 am, Chris [EMAIL PROTECTED] wrote:
   On Jun 2, 9:34 am, [EMAIL PROTECTED]

   [EMAIL PROTECTED] wrote:
Hi,

i am building a little script and i want to output a series of columns
more or less like this:

1  5  6
2  2  8
2  9  5
  ...

 I have a related question:

 Does Python have (or can emulate) the formatted output capability found in
 Perl?

 For example, all I have to do to get nicely formatted (i.e., aligned) output
 is provide values for special STDOUT variables (i.e., STDOUT_TOP, STDOUT,
 STDOUT_BOTTOM, etc.), exemplified by:

   format STDOUT_TOP =
   
 ---­---
   ~
   .

   format STDOUT =
   @  @  @
   $res-{'full_name'},  $res-{'phone_1'},         $res-{'phone_1_type'}
   @  @ ~
   $res-{'address_1a'},                $res-{'address_2a'}
   @  @ ~
   $res-{'address_1b'},                $res-{'address_2b'}
   @  @ ~
   $res-{'address_1c'},                $res-{'address_2c'}
   @  @ ~
   $city_1                              $city_2
   @  @ ~
   $res-{'email_1'},                   $res-{'email_2'}
   
 ---­---
   ~
   .

 Then, all I have to do is populate my $res object/hash as desired -- in this
 example simple the results of a SQL query -- and lastly just call the write
 function:

   write;

 and Perl will produce very nicely formatted results.  This is useful not only
 for producing human readable output, but also fixed-column-width data files,
 etc.  I'd love to learn the Pythonistic way of doing the same thing.

 Thanks!
 Doug

I didn't know you could do that in perl. Too bad I quit using it
when I switched to Python.

OTOH, I can do similar formatting directly in SQL.

In Access, I create a query with this SQL:

SELECT
 
Chr(10) 
Format$(SampleEventCode,!) 
Format$
(SampleEventDescr,) 
Chr(10) 
Format$(EventSortOrder,!) 
Format$(From:   Format$(DateFrom,/MM/
DD),) 
Chr(10) 
Format$(SampleEventReportLabel,!) 
Format$(To:   Format$(DateTo,/MM/
DD),)
AS Expr1
FROM tblSampleEvent;

Then I simply call it from Python. (I could call with the SQL code
instead of invoking the Access query, but the OBDC interface can't
process this particular SQL statement, tries to put brackets around
the format templates, so best render unto Access the things that
belong to Access.)

# code
import dbi
import odbc
con = odbc.odbc(BPWR)
cursor = con.cursor()
cursor.execute(
SELECT * FROM SQLFormatTest;
)
results = cursor.fetchall()
for i in results:
  for j in i:
print j
# /code

which prints


2000Q1 First Quarter of 2000
2000100 From: 2000/01/01
1st-Qtr 2000  To: 2000/03/31

2000Q2Second Quarter of 2000
2000200 From: 2000/04/01
2nd-Qtr 2000  To: 2000/06/30

2000Q3 Third Quarter of 2000
2000300 From: 2000/07/01
3rd-Qtr 2000  To: 2000/09/30

2000Q4Fourth Quarter of 2000
2000400 From: 2000/10/01
4th-Qtr 2000  To: 2000/12/31

2000Q1LF  Low Flow First Quarter of 2000
2000105 From: 2000/01/01
1st-Qtr 2000  To: 2000/03/31

2000Q2LOD LOD borings Second Quarter of 2000
2000206 From: 2000/04/01
2nd-Qtr 2000  To: 2000/06/30
.
.
.
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Re: Database Query Contains Old Data

[James A. Donald]

On Wed, 21 May 2008 07:23:04 -0700 (PDT), Paul Boddie 
 MySQL appears to use repeatable read by default [1] as its
 transaction isolation level, whereas PostgreSQL (for example) uses
 read committed by default [2]. I would guess that if you were using
 PostgreSQL, this particular problem would not have occurred, but there
 are other reasons to be aware of the effects of long duration
 transactions in PostgreSQL, and the practice of periodically
 performing a rollback would still be worth considering with that
 database system.

If one has transactions open for a long time, or transactions that
involve a great deal of data, this will result in poor performance or
poor scalability.  But one may have such large transactions without
being aware of it.  Is there any way to make transaction size salient
to the developer?  Any way to make sure one is committing as early and
often as possible?

--
  --
We have the right to defend ourselves and our property, because 
of the kind of animals that we are. True law derives from this 
right, not from the arbitrary power of the omnipotent state.

http://www.jim.com/  James A. Donald
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Importing xlrd

[Chanman]

This is probably a simple question to most of you, but here goes.
I've downloaded the xlrd (version 0.6.1) module and placed in in the
site-packages folder.  Now, when I write a script, I type:

import sys
import xlrd

When I run it, there is an import error saying there is no module
named xlrd.  However when I type sys.path, the site-packages folder is
definitely in the path.  Do I somehow need to run the xlrd setup.py
first before importing?

Any help would be appreciated.
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Re: Cast list of objects to list of strings

[Gary Herron]

bukzor wrote:

I have this function:

def write_err(obj):
 from sys import stderr
 stderr.write(str(obj)+\n)

and I'd like to rewrite it to take a variable number of objects.
Something like this:

def write_err(*objs):
 from sys import stderr
 stderr.write( .join(objs)+\n)

but I lose the property that the function works on any object. 


No you don't.   If you were happy with printing the str(...) of a single 
objects, why not just printout the (concatenation) of the str(...) of 
each of many objects?


stderr.write( .join([str(b) for b in objs])+\n)

Gary Herron





What's
the simplest way to fix this? In essence, I need to cast a list of
objects to a list of strings. I'd like to do just str(objs) but that
(obviously) doesn't quite do what I need.

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Re: Better performance

[David]

On Mon, Jun 2, 2008 at 4:42 AM, Franck Y [EMAIL PROTECTED] wrote:
 Hello Folks,

 I am facing a problem where i need to parse around 200 files, i have a
 bit of knowledge in PHP/Perl/Python (the magic P :-P)


Trite answer: Use whatever is going to work best in your circumstances.

All 3 languages can do what you need.

Strong points for the languages as related to your question:

PHP: Easy to make web pages.
Perl: Lots of libraries, good text processing support
Python: Easy to read and maintain

You could even use all 3, in their strong areas. eg, PHP for the web
page, perl for quick  dirty text-processing utils, and Python for the
longer, more complicated scripts which you have to maintain.

David.
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Re: Why does python not have a mechanism for data hiding?

[Carl Banks]

On Jun 2, 4:50 pm, Russ P. [EMAIL PROTECTED] wrote:
 On Jun 2, 6:41 am, Carl Banks [EMAIL PROTECTED] wrote:

  You are not realizing that only useful(**) thing about data hiding is
  that some code has access to the data, other code does not.  If you
  hide data equally from everyone it's just a useless spelling change.

 I think you're missing the point.

Well that's nice: you're accusing me of missing the point after having
quoted something I wrote as if it represented by own views, even
though I footnoted it and said I was only doing it for the sake of
argument.  Perhaps, outside this discussion, I am totally getting the
point.

I can't tell, though, because I read your post twice and I have no
idea what you consider the point to be.

Best as I can tell you are claiming that data hiding isn't important,
but then you go on to imply Python is blemished because it doesn't
hide data.  It really makes no sense: perhaps you can help us out by
giving us an example of something that illustrates what you're saying?


(FWIW, my actual view on the matter is I don't give a lick about data
hiding or marking internals.)

Carl Banks
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Re: Why does python not have a mechanism for data hiding?

[Russ P.]

On Jun 2, 3:04 pm, Carl Banks [EMAIL PROTECTED] wrote:
 On Jun 2, 4:50 pm, Russ P. [EMAIL PROTECTED] wrote:

  On Jun 2, 6:41 am, Carl Banks [EMAIL PROTECTED] wrote:

   You are not realizing that only useful(**) thing about data hiding is
   that some code has access to the data, other code does not.  If you
   hide data equally from everyone it's just a useless spelling change.

  I think you're missing the point.

 Well that's nice: you're accusing me of missing the point after having
 quoted something I wrote as if it represented by own views, even
 though I footnoted it and said I was only doing it for the sake of
 argument.  Perhaps, outside this discussion, I am totally getting the
 point.

 I can't tell, though, because I read your post twice and I have no
 idea what you consider the point to be.

 Best as I can tell you are claiming that data hiding isn't important,
 but then you go on to imply Python is blemished because it doesn't
 hide data.  It really makes no sense: perhaps you can help us out by
 giving us an example of something that illustrates what you're saying?

I think I made my point abundantly clear. I said that rigorously
denied access to encapsulated data is not important, but a clear
specification of what is intended for the client and what is intended
for internal use *is* important. And an ugly naming convention for
variable and function names is not the best way to do it.

I suggest you ask yourself why C++, Java, Ada, and probably most other
object-oriented languages, have encapsulation or data hiding. And
no, I am not claiming that *every* application written in Python needs
it, but certainly *some* could benefit from it.

 (FWIW, my actual view on the matter is I don't give a lick about data
 hiding or marking internals.)

What kind of programming do you do?
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Re: Merging ordered lists

[etal]

On Jun 1, 12:34 am, Raymond Hettinger [EMAIL PROTECTED] wrote:

 I would do it two steps.  There's a number of ways to merge depending
 on whether everything is pulled into memory or 
 not:http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/491285http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/305269

 After merging, the groupby itertool is good for removing duplicates:

    result = [k for k, g in groupby(imerge(*sources))]

 Raymond

Thanks for the tip; itertools never ceases to amaze. One issue:
groupby doesn't seem to remove all duplicates, just consecutive ones
(for lists of strings and integers, at least):

 [k for k, g in itertools.groupby(list(asdfdfffdf))]
['a', 's', 'd', 'f', 'd', 'f', 'd', 'f']


Another issue: dropping everything into a heap and pulling it back out
looks like it loses the original ordering, which isn't necessarily
alphabetical, but however the user wants to organize the
spreadsheet. That's why I originally avoided using
sorted(set(itertools.chain(*sources))). Do you see another way around
this?
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Re: ANN: equivalence 0.1

[George Sakkis]

On Mon, Jun 2, 2008 at 6:31 AM, Giuseppe Ottaviano [EMAIL PROTECTED] wrote:

 On Jun 1, 2008, at 6:16 PM, George Sakkis wrote:

 Equivalence is a class that can be used to maintain a partition of
 objects into equivalence sets, making sure that the equivalence
 properties (reflexivity, symmetry, transitivity) are preserved. Two
 objects x and y are considered equivalent either implicitly (through a
 key function) or explicitly by calling merge(x,y).

 I think this library would be very useful, and I like the interface (in
 particular the idea of the projecting function),

Thanks for trying it out!

 but I think the algorithm
 is less than optimal. It can show quadratic behavior in some cases:

 $ python -m timeit -s 'import equivalence' -s 'eq =
 equivalence.Equivalence()' 'for i in xrange(1): eq.merge(i, i+1)'
 10 loops, best of 3: 57.6 msec per loop

 $ python -m timeit -s 'import equivalence' -s 'eq =
 equivalence.Equivalence()' 'for i in xrange(1): eq.merge(i+1, i)'
 10 loops, best of 3: 2.59 sec per loop

Interesting.. it took me a while to figure out why the second case is
so much slower and you're right, it is indeed quadratic. I don't know
how likely would such pathological cases be in practice, given that
the preferred way to merge a batch of objects is
eq.merge(*xrange(10001)), which is more than 3 times faster than the
non-pathologic first case (and which I optimized even further to avoid
attribute lookups within the loop so it's more like 5 times faster
now). Also the batch version in this case remains linear even if you
merge backwards, eq.merge(*xrange(1,-1,-1)), or in any order for
that matter.

 Have you considered using the Union-Find algorithm, which would be (almost)
 linear in all cases?

I am familiar with it and I will certainly consider it for the next
version; for now I was primarily interested in functionality (API) and
correctness.

Thanks,
George
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Re: Why does python not have a mechanism for data hiding?

[Carl Banks]

On Jun 2, 6:39 pm, Russ P. [EMAIL PROTECTED] wrote:
 On Jun 2, 3:04 pm, Carl Banks [EMAIL PROTECTED] wrote:



  On Jun 2, 4:50 pm, Russ P. [EMAIL PROTECTED] wrote:

   On Jun 2, 6:41 am, Carl Banks [EMAIL PROTECTED] wrote:

You are not realizing that only useful(**) thing about data hiding is
that some code has access to the data, other code does not.  If you
hide data equally from everyone it's just a useless spelling change.

   I think you're missing the point.

  Well that's nice: you're accusing me of missing the point after having
  quoted something I wrote as if it represented by own views, even
  though I footnoted it and said I was only doing it for the sake of
  argument.  Perhaps, outside this discussion, I am totally getting the
  point.

  I can't tell, though, because I read your post twice and I have no
  idea what you consider the point to be.
  Best as I can tell you are claiming that data hiding isn't important,
  but then you go on to imply Python is blemished because it doesn't
  hide data.  It really makes no sense: perhaps you can help us out by
  giving us an example of something that illustrates what you're saying?

 I think I made my point abundantly clear. I said that rigorously
 denied access to encapsulated data is not important, but a clear
 specification of what is intended for the client and what is intended
 for internal use *is* important. And an ugly naming convention for
 variable and function names is not the best way to do it.

Well let me tell you what's confusing me here: I can't figure out, if
this is your standpoint, what issue you could have had with what I
said.  What specifically did you disagree with?  What did I say that
was wrong?  It seems like we are more in agreement than not.


 I suggest you ask yourself why C++, Java, Ada, and probably most other
 object-oriented languages, have encapsulation or data hiding. And
 no, I am not claiming that *every* application written in Python needs
 it, but certainly *some* could benefit from it.

I know what it's there for, chief.  That's exactly what I was saying
to Antoon, and you took issue with it and claimed I was missing the
point.  What gives?


Carl Banks
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Re: Cast list of objects to list of strings

[bukzor]

On Jun 2, 2:56 pm, jay graves [EMAIL PROTECTED] wrote:
 On Jun 2, 4:02 pm, Larry Bates [EMAIL PROTECTED] wrote:

  I think what you want is:
  def write_err(*args):
   from sys import stderr
   stderr.write(\n.join([str(o) for o in args]))

 Slight nitpick.  If you are using version = 2.4 you could use a
 generator expression instead of a list comprehension to avoid building
 and throwing away a list.

 \n.join(str(o) for o in args)

 http://www.python.org/dev/peps/pep-0289/

 Very unlikely to yield a material time difference in this case but
 cleaner IMO.

 ...
 Jay Graves

Thanks! That's exactly what I was looking for.
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Re: Checking each item in m.group()?

[rurpy]

[EMAIL PROTECTED] wrote:
 On Jun 2, 5:06 pm, Peter Otten [EMAIL PROTECTED] wrote:

 You are taking the wrong approach here.

 Don't build SQL statements as strings; you are enabling the next SQL
 injection attack. Pass parameters using the DB API instead.

 Don't use regular expressions to parse a CSV file. Python's csv module is
 more likely to deal correctly with the quirks of that standard.


 I'd like to second both these statements.  Regardless of whether these
 CSV files are from a trusted source or not, it's a virtual truism of
 programming that eventually, any application will be used in ways it
 was not intended.  Since using a parameterized query is a simple way
 to avoid a common security hole, even if such a thing could never be
 exploited by the app in its current configuration, you should do
 things the Right Way.  That way, even if your code is twisted to some
 other use in the future, it's less likely to cause problems.

I don't have a problem with a response saying it's
a good idea to use parameterized queries and explaining
why, but I have seen way too many responses like this
which are basically FUD.

I'm not sure what a virtual truism is, but if it is
like a truism, it's not true.  There are many cases
where one can accurately predict that the code will
not be used in the future in some different app.
I don't know what the OP was doing, but I have done
many data conversion jobs where I have done things
similar to the OP.  The jobs were one-time, move data
from system A to system B (with some munging in between)
and I could and did predict the conversion code would
not get reused.  My accuracy rate is 100%.
And if you do reuse code where you feed it untrusted
input in a security sensitive context,
and you don't bother to verify the security of said,
code, you already have so many problems, one more
probably won't make much difference.

To the OP:
The advice to use parameterized queries is good
but overstated.  There are cases when it is quite
safe to use non-parameterized statements:
* When you control the data going into the query
  )e.g., you've generated it yourself).
* When the data come from trusted sources (including
  something like sys.input if the only people with
  access to the program are trusted).
* When you can reliably check the data yourself,
  for example in:
sql = SELECT * FROM foo WHERE id=%d % int(some_string)
cursor.execute (sql)
 it doesn't really matter what some_string contains
 (if you are prepared for a Python exception).  But
 note that checking and escaping strings in more general
 or complicated cases can be quite tricky.)

In most cases a good reason to use a parameterized query
is that it is no harder than to not use one, so why
not and get the additional safety for free?  A parameterized
query can often run faster than a non-parameterized one
since the database can reuse the cached compiled query.
(But sometimes the opposite is true, see below).
A parameterized form of the above is:

sql = SELECT * FROM foo WHERE id=? % int(some_string)
cursor.execute (sql, int(some_string))

so it is just as easy.  There are times though when
it is slightly harder.  If idnums is an arbitrary list
of ints:

sql = SELECT * FROM foo WHERE id IN(%s) % ','.join(idnums)
cursor.execute (sql)

Using a parameterized query might look like:

sql = SELECT * FROM foo WHERE id IN(%s) %
','.join(['?']*len(idnums))
cursor.execute (sql, idnums)

When you have written such code a few times it becomes
a natural idiom, but if you only do so occasionally,
you are in a hurry, and the conditions above apply,
then there is no reason not to go with the first form.

And if you you already have a text string of comma-separated
digits, the ease of using the direct sql form becomes
even greater:

sql = SELECT * FROM foo WHERE id IN(%s) % idnums_string
cursor.execute (sql)

But of course, if idnums_strings came from an untrusted
source, then you need to validate it first, e.g.:

if idnums_string.strip(0123456789 ,): then raise Error

There are also times when using a parameterized query
can dramatically (and I mean two or three *orders of
magnitude*) slow down your query when using prepared
queries.  For example:

sql = SELECT * FROM foo WHERE txt LIKE %s%% % some_string
cursor.execute (sql)

can be expected to run quite quickly in most database
systems, since the database knows that the searched for
text starts with a constant string and can thus use an
index.  The parameterized form:

sql = SELECT * FROM foo WHERE txt LIKE ?
cursor.execute (sql, [some_string + %])

will often run very very slowly, because when the query
is prepared the database has no idea if the argument
will start with a constant string of not, and thus can
only assume the worst, and prepare the query so that
it doesn't use an index.

The bottom line is, as in all things, understanding
the issues will lead to much better decisions than
blindly following some dumbed down 

Re: Code correctness, and testing strategies

[Jacob Hallen]

In article [EMAIL PROTECTED],
David  [EMAIL PROTECTED] wrote:
 Clients generally require *working* software. Unfortunately it is all too
 easy to ship something broken because then you can claim you completed the
 coding on time and any slippage gets lost in the next 5 years of
 maintenance.

That's why you have human testing  QA. Unit tests can help, but they
are a poor substitute. If the customer is happy with the first
version, you can improve it, fix bugs, and add more unit tests later.

The most important aspect of usnit testing is actually that it makes the code 
testable.
This may sound lik an oxymoron but it is actually a really important property. 
Testable
code has to have a level of modularity as well as simplicity and clarity in its
interfaces that you will not achieve in code that lacks automated unit tests.

You can easily convince yourself that this is true by adding complete coverage 
unit
tests to some code after you have written it. It's tough work and more often 
than
not, you need to refactor the code to make it testable.

Another aspect that you are raising is the use of human testing and QA. I agree 
that
these are important, but every bug they discover is a failure of the developers 
and
their tests. Our testers can sail through a testbed in 30 minutes if there are 
no bugs.
Every single bug adds 30-60 minutes of testers time in order to pinpoint the bug
and supply the developers with enough information to locate and fix it. Add some
10 minutes to testing time on the next testbed to verify that the bug is 
actually
fixed. In my end of the world, tester time is not cheaper than developer time. 
It
is also a scarcer resource than developer time.

The roundtrips between developers and testers also add to real required to 
develop
the product. There will always be delays introduced by having to produce the 
tester
with a testable system, wait for the tests to happen, have the report written up
and allocated to a developer etc. With TDD most of these bugs will be caught
in a no-delay loop at the developers desk.

This last fact has another important property that is easily overlooked. Once 
the
off-by-one errors and other trivial bugs don't clutter the minds of the testers
they will start thinking more clearly about the application and where the really
nasty bugs are found - the ones where your thinking went wrong but your 
implementation
is correct. if the testers are busy tracking trivial bugs, your customers will
find the nasty one. If you are lucky, they will tell you.

Jacob Hallén

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Re: Checking each item in m.group()?

[Gilles Ganault]

On Mon, 2 Jun 2008 12:06:21 -0700 (PDT), Matimus [EMAIL PROTECTED]
wrote:
Here is a brief example. Note that this code is very insecure and
susceptible to a SQL injection attack. Hopefully these csv files are
from a trusted source.

Yes they are, and this script will only run on my PC, so it doesn't
need to be more secure than this.

sql = INSERT INTO mytable (col1, col2) VALUES ('%s','%s')%tuple(
(c, NULL)[c == ''] for c in m.groups()
)


I don't understand this syntax :-/

Also, check out the csv module for parsing your csv file.

Will do. Thank you.
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Re: Why does python not have a mechanism for data hiding?

[Russ P.]

On Jun 2, 4:17 pm, Carl Banks [EMAIL PROTECTED] wrote:
 On Jun 2, 6:39 pm, Russ P. [EMAIL PROTECTED] wrote:



  On Jun 2, 3:04 pm, Carl Banks [EMAIL PROTECTED] wrote:

   On Jun 2, 4:50 pm, Russ P. [EMAIL PROTECTED] wrote:

On Jun 2, 6:41 am, Carl Banks [EMAIL PROTECTED] wrote:

 You are not realizing that only useful(**) thing about data hiding is
 that some code has access to the data, other code does not.  If you
 hide data equally from everyone it's just a useless spelling change.

I think you're missing the point.

   Well that's nice: you're accusing me of missing the point after having
   quoted something I wrote as if it represented by own views, even
   though I footnoted it and said I was only doing it for the sake of
   argument.  Perhaps, outside this discussion, I am totally getting the
   point.

   I can't tell, though, because I read your post twice and I have no
   idea what you consider the point to be.
   Best as I can tell you are claiming that data hiding isn't important,
   but then you go on to imply Python is blemished because it doesn't
   hide data.  It really makes no sense: perhaps you can help us out by
   giving us an example of something that illustrates what you're saying?

  I think I made my point abundantly clear. I said that rigorously
  denied access to encapsulated data is not important, but a clear
  specification of what is intended for the client and what is intended
  for internal use *is* important. And an ugly naming convention for
  variable and function names is not the best way to do it.

 Well let me tell you what's confusing me here: I can't figure out, if
 this is your standpoint, what issue you could have had with what I
 said.  What specifically did you disagree with?  What did I say that
 was wrong?  It seems like we are more in agreement than not.

  I suggest you ask yourself why C++, Java, Ada, and probably most other
  object-oriented languages, have encapsulation or data hiding. And
  no, I am not claiming that *every* application written in Python needs
  it, but certainly *some* could benefit from it.

 I know what it's there for, chief.  That's exactly what I was saying
 to Antoon, and you took issue with it and claimed I was missing the
 point.  What gives?

 Carl Banks

I thought you were saying that encapsulation or so-called data
hiding is worthless. If I misunderstood you, then I apologize. I
don't have time to go back and sort it all out.

Here's what I think Python should have. I think it should have a
keyword, something like priv, to identify data or functions as
private. As I said earlier, private for class data or functions
(methods) could be implemented like protected in C++. That means
that derived classes would have access to it, but clients of the class
would not. If the client really needs or wants access, he could be
given a sort of back door access similar to the current Python rule
regarding double leading underscores. Thus, the client would have
access, but he would know very well that he is using something that
the original designer did not intend for him to use.

It's just a suggestion. I'm not a language expert, and I realize that
I could be missing something important.

I also realize, by the way, that Python allows a client of a class to
define a new class member from completely outside the class
definition. Obviously, that cannot be declared private. But if the
same identifier is already declared private within the class, than the
new definition should not be allowed (because it would defeat the
whole idea of private class members).
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Ideas for master's thesis

[Filip Gruszczyński]

Hello there,

I am student of CS at the University of Warsaw, currently 4th year. I
am attending Object Oriented Programming seminar and it is about time,
I started looking for an idea of my master's degree project. As I like
Python very much, I would like to do something with this language, yet
I don't know if there are any needs/science fields, that could be used
as a basis for a thesis. Therefore I would like to ask, if there is
any way to access any person involved in development, who would help
me find some field that need to be developed/researched (rather the
first one) and would be close enough to the OOP, so I could present it
to a mentor (he is cool with doing something for OSS community).

-- 
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Re: Why does python not have a mechanism for data hiding?

[Paul Rubin]

Russ P. [EMAIL PROTECTED] writes:
 I also realize, by the way, that Python allows a client of a class to
 define a new class member from completely outside the class
 definition. Obviously, that cannot be declared private. 

This is bogus about 95% of the time though.  For the cases where it is
really desired, I think it's best to require the target class to be
enable it specifically somehow, maybe by inheriting from a special
superclass.  That could let the compiler statically resolve member
lookups the rest of the time.

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Re: Why does python not have a mechanism for data hiding?

[Carl Banks]

On Jun 2, 7:41 pm, Russ P. [EMAIL PROTECTED] wrote:
 I thought you were saying that encapsulation or so-called data
 hiding is worthless. If I misunderstood you, then I apologize. I
 don't have time to go back and sort it all out.

No, not at all.  I was suggesting that Antoon's example of data hiding
wasn't useful because it didn't really hide data: it was merely a
spelling change.

(I'm not, mind you, saying that it's ordinarily a good trade-off to
encapsulate data, but I do get the point of it.)


 Here's what I think Python should have. I think it should have a
 keyword, something like priv, to identify data or functions as
 private. As I said earlier, private for class data or functions
 (methods) could be implemented like protected in C++. That means
 that derived classes would have access to it, but clients of the class
 would not. If the client really needs or wants access, he could be
 given a sort of back door access similar to the current Python rule
 regarding double leading underscores. Thus, the client would have
 access, but he would know very well that he is using something that
 the original designer did not intend for him to use.

Reasonable enough.  I've always thought C++ should have a
private_cast.


Carl Banks
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Re: Importing xlrd

[Gary Herron]

Chanman wrote:

This is probably a simple question to most of you, but here goes.
I've downloaded the xlrd (version 0.6.1) module and placed in in the
site-packages folder.  Now, when I write a script, I type:

import sys
import xlrd

When I run it, there is an import error saying there is no module
named xlrd.  However when I type sys.path, the site-packages folder is
definitely in the path.  Do I somehow need to run the xlrd setup.py
first before importing?

Any help would be appreciated.
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On what system?  Windows or Unix?  Which download?  The exe or the zip?

I'm guessing you downloaded the zip file on a Unix or Linux system.  If 
so, you should not copy the files into the site-package directory 
yourself.  You are supposed to use the included setup.py file like this:


 unzip into some local directory
 cd into that directory
 python setup.py build
 python setup.py install

Then your import should work fine.


Gary Herron

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Re: Why does python not have a mechanism for data hiding?

[Carl Banks]

On Jun 2, 10:14 am, Antoon Pardon [EMAIL PROTECTED] wrote:
 On 2008-06-02, Carl Banks [EMAIL PROTECTED] wrote:



  On Jun 2, 9:07 am, Antoon Pardon [EMAIL PROTECTED] wrote:
  On 2008-06-02, Carl Banks [EMAIL PROTECTED] wrote:

   On Jun 2, 6:40 am, Antoon Pardon [EMAIL PROTECTED] wrote:
   On 2008-06-02, Carl Banks [EMAIL PROTECTED] wrote:

On Jun 2, 5:38 am, Antoon Pardon [EMAIL PROTECTED] wrote:
If you really need it, you can do data hiding in python. It just
requires a bit more work.

- Hide.py 
-
class Rec(object):
 def __init__(__, **kwargs):
 for key,value in kwargs.items():
 setattr(__, key, value)

 def __getitem__(self, key):
 return getattr(self, key)

 def __setitem__ (self, key, val):
 setattr(self, key, val)

class Foo(object):

  def __init__(self):

hidden = Rec(x=0, y=0)

def SetX(val):
  hidden.x = val

def SetY(val):
  hidden.y = val

def GetX():
  return hidden.x

def GetY():
  return hidden.y

self.SetX = SetX
self.SetY = SetY
self.GetX = GetX
self.GetY = GetY

In other words, it's a useless no-op.

In fact, I'd say this is even worse than useless.  Creating accessor
functions is a sort of blessing for external use.  Knowing that there
are accessor functions is likely to cause a user to show even less
restraint.

   I think you completed missed the point.

   I'm not sure I missed the point so much as I failed to read your mind.

  Fine with me, it is just the other side of the coin.

   This is just a proof of concept thing. In a real example there would
   of course no Set en Get methods but just methods that in the course
   of their execution would access or update the hidden attributes

   Fair enough, but I don't see anything in your example that suggests a
   way to discriminate between access from within the class and access
   from outside the class, which is the crucial aspect of data hiding.

  The fact is that hidden and its attributes are not accessible from
  outside the instance. They are only accessible to the local functions
  of __init__. By binding those local functions as atributes to the
  instance, hidden can be modified by what for all practical purposes
  looks like a method call, but really is a closure call.

  You haven't hidden the data at all, all you've done is to change the
  means of accessing it.  What difference does it make whether I write
  foo.getX() or foo.x?  Everyone in the world still has full access to
  the data.

 Can't you look beyond the specific example? The GetX is just an example.
 Any local function of __init__ has access to hidden and its attributes
 and could manipulate them, even if the class wouldn't define getters
 and setters.

Ok.  You could have made the proof-of-concept-ness of your example
more clear by not, you know, binding those local functions to globally
accessable names, thus thwarting your own concept.

But still, we all knew functions could do that.  How could you make
data private to a group of functions (like, say, methods of a class,
or all functions in a module).  It seems you'd have to define all
functions in the the same function scope, instead of where they'd more
naturally be defined (in the class or module scope).  Unwieldy to say
the least, but doable, I suppose.


Carl Banks
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