date:20060702

Vlad Dogaru [EMAIL PROTECTED] wrote:

 Hello,
 
 I would like to learn web scripting with Python (sure, everyone uses
 PHP, but I don't like the syntax and Python is more general-purpose
 and... well, I guess you people know the advantages better than me).
 Where can I get a thorough introduction to both CGI and using Python
 for CGI? That includes installing my own web server (at home, for
 testing) and starting from scratch (by that I mean I have near null
 experience with CGI).
 
 I have tried looking through the source code of MoinMoin, but it's just
 too advanced for me -- I simply don't know where to start. Right now,
 I'll take any and all suggestions. However, please suggest books or
 articles that are up-to-date on Python programming; I'd hate to see
 that I'm studying obsolete texts or the like.

In terms of learning, Steve Holden's Python Web Programming is still
unbeatable -- it teaches you just enough of the many underlying
technologies, from HTTP to HTML to relational databases, as well as
Python.  However, it IS an old version of Python (sigh).  But it's very
easy to learn the relatively small enhancements to the Python language
since the time Steve penned his masterpiece... anything that used to
work then still works now, you have better ways to perform many tasks
(particularly thanks to additions to the standard library, and third
party extension modules matured in the meantime) but those are easy to
learn afterwards (and meanwhile, a solid understanding of the basics
of, say, HTTP and entity-relation design, will stand you in good stead
for years and years to come!-).  Steve's book is really the best you can
get, for learning purposes such as yours.  However...L

If you insist on getting coverage of the latest and greatest version of
Python, you might want to get the 2nd edition of my Python in a
Nutshell, due out later this month; it strives to cover Python 2.5
(also due out later this month;-) as well as 2.4 (the still-now current
version, on which the new Nutshel focuses), and does have a chapter
specifically on CGI (not much changed from the first edition's, of
course, since CGI itself has not changed much over the years;-).

To have a look at my book (and just about any other O'Reilly book... and
not just O'Reilly either!) for free, subscribe to O'Reilly's Safari
online library -- I believe the first two weeks are free, so, as long as
you cancel in time, you should not have to pay a penny for the
privilege; thus, it may be a good idea (I personally like having access
to said library for searches etc, but that's a separate issue).  It will
be a while before the 2nd edition gets online -- but as I said the CGI
part is basically unchanged anyway.

But, talking of web resources...:

A Google search for Python CGI gives you 20 million hits, and quite a
few of those appear to be good tutorials on the subject -- why don't you
give those a try, first?  Sure, most of the pages will be using older
versions of Python -- but most of the differences should be of little
importance. One crucial one: you *DO* want to use the cgitb auxiliary
module to get good tracebacks in case of errors, and older sites may not
mention it -- however, that's pretty simple indeed...:

  import cgitb; cgitb.enable()

just place this line at the very top of your CGI script (after the
shebang line and the docstring, heh:-) and you're all set.  Any
further info you need for advanced usage of cgitb is in one tiny page
at http://docs.python.org/lib/module-cgitb.html.


Alex
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Re: Dictionary .keys() and .values() should return a set [with Python 3000 in mind]

Nick Vatamaniuc wrote:
 Robert Kern wrote:
  [EMAIL PROTECTED] wrote:
   The same thing goes for the values(). Here most people will argue that
...
 
  This part is pretty much a non-starter. Not all Python objects are hashable.
...
  Also, I may need keys to map to different objects that happen to be equal.
 
  --
  Robert Kern
 


So, values() can't return a set because of (at least) the two reasons
given above.  And since, as Scott David Daniels pointed out, dicts
support the iterator protocol, you can ask for a set of the keys easily
enough if you want it:

 d = dict(a=1, b=2, c=3)
 set(d)
set(['a', 'c', 'b'])

So, IMHO, there's not much point to having keys() return a set.


Peace,
~Simon

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Re: How to create a limited set of instanceses of a class

madpython [EMAIL PROTECTED] wrote:

 Thanks Alex and Scott for your lead. It would've taken me forever
 trying to figure it out by myself :)
 
 I am affraid I didn't specify initially one thing and that led to a
 confusion: there is no need to pick an instance from the weakref
 dictionary, just return None if there are already 5 instances. But on
 the other hand if a hardref to an object was deleted, it's place can be
 taken by another one.

And the latter issue is what the use of weakref in both responses was
about.

 Here's what i mean (and where the problem is):
 
 #build a list of 5 elements
 instList=[]
 for i in range(7):
   ainst=A()
   if ainst:
   instList.append(ainst)

Note that this is quite sloppy:

-- test if ainst is None: -- no excuse to use just if ainst:
-- at the end of the loop ainst remains bound -- del ainst to avoid
   ainst being an extra reference to the instance

neither of these explains your bug, but -- just tighten up your code,
it's a good idea!-)

 
 for i in range(5):
   instList.remove(instList[0]) #here the hardref is deleted

SUPER sloppy!  Just del instList[0] for the same effect much better
obtained.

   ainst=A()
   while not ainst:
   #make shure that ainst is not NoneType

Again, while ainst is None: would be far better.

   gc.collect()
   time.sleep(1)   #wait 1 sec for gc() to clean the memory

Useless, gc.collect() is synchronous *AND* only cleans up CYCLIC garbage
anyway -- unless instances of A have reference loops, both lines are
useless (the sleep is useless in ANY case).

   ainst=A()   #try again
   instList.append(ainst) #new object added
 
 the priblem is that ~3 out of 10 times the test part run into infinite
 loop because of unsatisfied condition (while not ainst:) - memory
 cannot be freed therefore new instance of A isn't permitted.

Your test code below does NOT do what your code here does!  Instead it
removes (in the worst possible way, rather than cleanly, but, no matter)
a RANDOM reference -- which may happen to be the same as item had left
over from the previous run... because of a printing loop that is in your
sample below and not here... which is where the sloppiness catches up on
you.  Specifically, look at this code from the sample that you had
below:

 #delete and recreate an arbitrary element in the instList
 for i in range(len(instList)):
 instList.remove(instList[random.choice(range(len(instList)))])
 ainst=A()
 while not ainst:#here is an unstable part
 ainst=A()   #sometimes the loop becomes infinite
 print gc.collect()  #decpite the explicit call for gc() to start
 time.sleep(1)
 print *, len(instList), len(A._weakrefdict)
 instList.append(ainst)
 for item in instList:
 print item.getId(), -- ,item.instCounter
 #print --- ,item
 print 

after the printing loop, name 'item' remains bound to the object that is
last element of instList -- so if that one just happens to be the
element you remove in that horrid first line of the main (outer) loop, 5
instances of class A nevertheless remain alive and therefore ainst will
be None forevermore, despite all the useless calls to gc.collect and
sleep.

A decent way to code this functionality would be:

# delete and recreate an arbitrary element in the instList
for i in range(len(instList)):
del instList[random.randrange(len(instList))]
instList.append(A())
for item in instList:
print item.getId(), -- ,item.instCounter
del item
print 

It would be nice to also print len(instList) and the length of the
weakref dictionary of class A, to doublecheck things, but you've made
life extremely hard for yourself by naming the latter with TWO leading
underscores instead of one, thus asking Python to name-mangle it to make
it very inconvenient to access.  Avoid the two-leading-underscores
construct (use just ONE leading underscore -- no mangling, no problems)
unless and until you are positive that you know exactly what you're
doing and are certain that you need the two underscores in a given
specific case -- do *NOT* default to using two underscores and make
life uselessly hard for yourself in terms of introspection and
debugging.

And, read up on such issues as del somelist[index] being WAY better
than somelist.remove(somelist[index]) and the way names, references,
objects and garbage collection work in Python...


Alex
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Python Challenge - thesamet unreachable?

2006-07-02 Thread [EMAIL PROTECTED]

If anyone has a way to contact thesamet, please tell him to check his
private messages at the Python Challenge website; I have a couple of
ideas for more challenges.

Cheers all.

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Re: PyPy and constraints

2006-07-02 Thread Ziga Seilnacht

Paddy wrote:
 I followed the recent anouncement of version 0.9 of PyPi and found out
 that there was work included on adding constraint satisfaction solvers
 to PyPy:
   http://codespeak.net/pypy/dist/pypy/doc/howto-logicobjspace-0.9.html

 I was wondering if this was a possibiity for mainstream python, and
 wether the the algorithms used could handle the kind of use mentioned
 here:

 http://groups.google.com/group/comp.lang.python/browse_frm/thread/d297170cfbf1bb34/d4773320e3417d9c?q=constraints+paddy3118rnum=3#d4773320e3417d9c

 Thanks, Paddy.

See: http://www.logilab.org/projects/constraint

Hope this helps,
Ziga

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Re: Can I do it using python?? about xterm and telnet

2006-07-02 Thread Network Ninja


valpa wrote:
 I'm a net admin for about 20 unix servers, and I need to frequently
 telnet on to them and configure them.
 It is a tiring job to open a xterm and telnet, username, password to
 each server.

 Can I  do it automatically by python? After that, there have 20 xterm
 consoles opened and telneted to their corresponding servers. Then I
 could start to type command in these xterms.


I often have to add users/delete local user accounts on routers and
switches. Each account is a local account, and I got tired of it. My
very first python program was created to use the telnetlib, and either
add, delete, or show a list of user accounts. It was very effective,
because it would change the same accounts on each router and switch.
Saved me a bunch of time, and got me hooked on python. If you are not
concerned about security, the telnetlib in python will help you.
Otherwise, use ssh, as it is more secure. You can even impliment
public/private keys for password-less log on. If you want some help
with the code for the telnetlib, let me know.

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Re: How to create a limited set of instanceses of a class

2006-07-02 Thread madpython

Thanks, Alex, again. The lesson has been taught. I appreciate very much
you spent time trying to help. Indeed the culprit of that infrequent
infinite loops was that bound reference item in the printing
loop. But frankly i thought that it only existed inside that loop.
Apparently I was wrong and glad that it was revealed.
I guess unless there is something  to add here the problem is solved
and subject is closed. Thanks everyone who took their time to ponder on
it. I hope it was as much educational for you as it was for me.

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Re: I have 100 servers which need a new backup server added to a text file, and then the backup agent restarted.

2006-07-02 Thread Ove Pettersen

gavino wrote:
 This seems easy but I have been asking tcl and python IRC chat all day
 and no one gave an answer.
 I have 100 servers which need a new backup server added to a text file,
  and then the backup agent restarted.
 If I have a list of the servers, all with same root password, and the
 connection is ssh.
 How do I connect to the server, cat the line to the config file, stop
 adn start the agent, and then do same to next server in list and
 iterate through the 100 servers. 
 What script would allow this?
 

I wouldn't use python at all (like swearing on this list???)  simple 
shell-command is more than sufficient.

for server in server1 server2 server3  server100
do
ssh [EMAIL PROTECTED] (echo new line  config.file; stop-command ; 
sleep 5 ; start-command)
done

I would however have extended the procedure with a few more checks...
Like:
* only add new line to config-file if it isn't present
* only do restart if config-file was modified

Regards,
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Re: Dictionary .keys() and .values() should return a set [with Python3000 in mind]

2006-07-02 Thread Terry Reedy

The meaning of dict.keys, etc, will not change for the 2.x series.  For 
3.0, I believe that Guido already intends that .keys() no longer return a 
separate list.  For one thing, a major, if not the main use, of the method 
is for iteration, as in 'for keys in d.keys():'.  For this, creating and 
them discarding a separate list is inefficient and, in a sense, silly.

One option is to make .keys be what .iterkeys is today.  Another, more 
recent, is to make .keys return a new iterable dict view object, details 
not yet worked out.  Either way, one would make an independent set or list 
with set(d.keys()) or list(d.keys)).

Terry Jan Reedy



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wanted: framework for creating nice step by step graphical visualisations of running Python code

2006-07-02 Thread Claudio Grondi


Today I bumped by chance into explaining what algorithms do by using 
animation (Java applets):
   http://www-sr.informatik.uni-tuebingen.de/~buehler/BM/BM1.html

Is there any tool in Python (except pyGame, Tkinter or other general 
purpose visualization tools) I am not aware of which would make it easy 
to create a similar, animated run through Python script code?

A free debugging tool capable of stepping line by line through Python 
code showing values of selected objects will do as a first approach, but 
it would be nice to be able to output also some graphics and/or text 
like it is done in the mentioned above example at pre-defined points in 
code called there
   /* visualisation step */

Any hints towards getting or constructing such a framework are welcome.

Claudio Grondi
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Re: I have 100 servers which need a new backup server added to a text file, and then the backup agent restarted.

2006-07-02 Thread Petr Jakeš

g This seems easy but I have been asking tcl and python IRC chat all day
g and no one gave an answer.
g I have 100 servers which need a new backup server added to a text file,
g  and then the backup agent restarted.
g If I have a list of the servers, all with same root password, and the
g connection is ssh.
g How do I connect to the server, cat the line to the config file, stop
g adn start the agent, and then do same to next server in list and
g iterate through the 100 servers. 
g What script would allow this?

Maybe webmin could help. http://www.webmin.com/
You can manage cluster of servers at once.

Petr Jakes

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Re: How to create a limited set of instanceses of a class

madpython [EMAIL PROTECTED] wrote:

 Thanks, Alex, again. The lesson has been taught. I appreciate very much
 you spent time trying to help. Indeed the culprit of that infrequent
 infinite loops was that bound reference item in the printing
 loop. But frankly i thought that it only existed inside that loop.
 Apparently I was wrong and glad that it was revealed.

Right -- a loop per se (be it a while loop or a for loop), just like an
if statement or a try statement, is NOT a separate scope from the code
around it (neither is a list comprehension); _functions_ are separate
scopes, and so are genexps.


Alex
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Re: Can I do it using python?? about xterm and telnet

2006-07-02 Thread [EMAIL PROTECTED]

I used this _EXACT_ solution(copied below) at work a month ago, to
start 20ish programs, each with different settings.  In this case I HAD
to use telnet for some of them, because they were on an embedded
machine, 4 of them used SSH(across the internet), and the rest were
local programs.  It worked flawlessly each time (every restart of the
network... which was quite often in this case).  There may be more
integrated solutions which solve the problem, but expect is rediculousy
easy to use, and is very deterministic as long as the commands work.
If the commands fail to work (such as someone deletes your program),
debugging is rather difficult, but at least you have a full dump of
everything sent by the server (because pexpect prints it all to the
screen).  Also, once the connection is open, you can call
conn.interact() and it will make the terminal interactive, just like
any other shell.


vasudevram wrote:
 Just FYI - pexpect is a Python app that works like Expect - which is by
 Don Libes and written in TCL. Expect comes with most Linux
 distributions and is available for most UNIX / Linux versions from its
 web site http://expect.nist.gov/

 The expect man page is enough to get started for simple needs, such as
 yours appears to be. You might want to play around with the original
 Expect a bit and then try out pexpect  - or you could just use Expect
 itself for your needs.

 HTH
 Vasudev
 ---
 Vasudev Ram
 Independent software consultant
 http://www.geocities.com/vasudevram
 PDF conversion toolkit:
 http://sourceforge.net/projects/xtopdf
 ---


 faulkner wrote:
  try pexpect.
  http://pexpect.sourceforge.net/
 
  valpa wrote:
   I'm a net admin for about 20 unix servers, and I need to frequently
   telnet on to them and configure them.
   It is a tiring job to open a xterm and telnet, username, password to
   each server.
  
   Can I  do it automatically by python? After that, there have 20 xterm
   consoles opened and telneted to their corresponding servers. Then I
   could start to type command in these xterms.
   
   Any suggestion appreciate. Much thanks.

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RE: xpath question

hi

is there anyone with XPath expertise here? i'm trying to figure out if
there's a way to use regex expressions with an xpath query? i've seen
references to the ability to use regex and xpath/xml, but i'm not sure how
to do it...

i have a situation where i have something like:
 /html/table//[EMAIL PROTECTED]'foo']

is it possible to do soomething like [EMAIL PROTECTED]/fo/] so i'd match the 
class
attribute with fo

i'm trying to parse HTML/Web docs...

thanks

-bruce


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Re: xpath question

bruce wrote:
 hi

 is there anyone with XPath expertise here? i'm trying to figure out if
 there's a way to use regex expressions with an xpath query? i've seen
 references to the ability to use regex and xpath/xml, but i'm not sure how
 to do it...

 i have a situation where i have something like:
  /html/table//[EMAIL PROTECTED]'foo']

 is it possible to do soomething like [EMAIL PROTECTED]/fo/] so i'd match the 
 class
 attribute with fo

 i'm trying to parse HTML/Web docs...

 thanks

 -bruce

I'll take this one...

Dude,  this is a *python* mailing list, not an xml/xpath/regex one.  In
addition, the regex syntax you're using above (~=/fo/) looks like
*perl* code--  but I wouldn't know 'cause I don't use perl myself.

Now it's entirely possible that there are *many* people here that are
xml/xpath/regex Kung Fu Masters,  *and* it's entirely possible that one
or more of them are about to answer your question informatively and in
exhaustive detail.  It's also entirely possible that this is the most
friendly and informative reply that you're going to get, here.


Try a more appropriate newsgroup, and good luck.

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Re: Computer Industry Workers May Face Cancer Risks

2006-07-02 Thread Cydrome Leader

In comp.unix.solaris [EMAIL PROTECTED] wrote:
 Computer Industry Workers May Face Cancer Risks
 
 http://www.studyandjobs.com/Comp_worker_cancer.html
 
 or visit
 http://www.studyandjobs.com/Cancer.html
 
 Regards

worthless add banner site
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RE: xpath question

simon..

you may not.. but lot's of people use python and xpath for html/xml
functionality.. check google python xpath...

later..


-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf
Of Simon Forman
Sent: Sunday, July 02, 2006 2:10 PM
To: python-list@python.org
Subject: Re: xpath question


bruce wrote:
 hi

 is there anyone with XPath expertise here? i'm trying to figure out if
 there's a way to use regex expressions with an xpath query? i've seen
 references to the ability to use regex and xpath/xml, but i'm not sure how
 to do it...

 i have a situation where i have something like:
  /html/table//[EMAIL PROTECTED]'foo']

 is it possible to do soomething like [EMAIL PROTECTED]/fo/] so i'd match the 
 class
 attribute with fo

 i'm trying to parse HTML/Web docs...

 thanks

 -bruce

I'll take this one...

Dude,  this is a *python* mailing list, not an xml/xpath/regex one.  In
addition, the regex syntax you're using above (~=/fo/) looks like
*perl* code--  but I wouldn't know 'cause I don't use perl myself.

Now it's entirely possible that there are *many* people here that are
xml/xpath/regex Kung Fu Masters,  *and* it's entirely possible that one
or more of them are about to answer your question informatively and in
exhaustive detail.  It's also entirely possible that this is the most
friendly and informative reply that you're going to get, here.


Try a more appropriate newsgroup, and good luck.

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newbie graphing recommendations ?

2006-07-02 Thread Adam


Where should a py newbie start to do some 2D graphs on screen ? 

PythonGraphApi, 
Gato, looks interesting 
pygraphlib, 
matplotlib, 

is there a best native Python place to start ? 



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Re: I have 100 servers which need a new backup server added to a text file, and then the backup agent restarted.

2006-07-02 Thread Michael Abbott

Ove Pettersen [EMAIL PROTECTED] wrote:
 for server in server1 server2 server3  server100; do

Two comments:

1.  Leave out the quotes(!)

2.  Either iterate as
   for server in $(seq -fserver%g 100); do
or, probably better
   for server in $(cat server-list); do
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Re: wanted: framework for creating nice step by step graphical visualisations of running Python code

2006-07-02 Thread bearophileHUGS

I remember Gato:
http://gato.sourceforge.net/
It animates only algorithms on graphs, but it seems a starting point,
and it works.

I vaguely remember another system, but probably not very good.

Bye,
bearophile

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Re: newbie graphing recommendations ?

2006-07-02 Thread Scott David Daniels

Adam wrote:
 Where should a py newbie start to do some 2D graphs on screen ? 
 PythonGraphApi, 
 Gato, looks interesting 
 pygraphlib, 
 matplotlib, 
 is there a best native Python place to start ? 

Check VPython (maybe least learning effort to first usable graphs).
Also look at PyGame if you want to paint screens.

--Scott David Daniels
[EMAIL PROTECTED]
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Re: languages with full unicode support

2006-07-02 Thread Matthias Blume

Oliver Bandel [EMAIL PROTECTED] writes:

Oliver Bandel wrote:

こんいちわ Xah-Lee san ;-)

Uhm, I'd guess that Xah is Chinese. Be careful
with such things in real life; Koreans might
beat you up for this. Stay alive!
 And the Japanese might beat him up, too.  For butchering their
 language. :-)

 OK, back to ISO-8859-1 :)  no one needs so much symbols,
 this is enough: äöüÄÖÜß :)

There are plenty of people who need such symbols (more people than
those who need ß, btw).

Matthias

PS: It should have been こんにちは.
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Ziga Seilnacht wrote:
Paddy wrote:
I followed the recent anouncement of version 0.9 of PyPi and found out
that there was work included on adding constraint satisfaction solvers
to PyPy:
http://codespeak.net/pypy/dist/pypy/doc/howto-logicobjspace-0.9.html

I was wondering if this was a possibiity for mainstream python, and
wether the the algorithms used could handle the kind of use mentioned
here:

http://groups.google.com/group/comp.lang.python/browse_frm/thread/d297170cfbf1bb34/d4773320e3417d9c?q=constraints+paddy3118rnum=3#d4773320e3417d9c

Thanks, Paddy.

See: http://www.logilab.org/projects/constraint

Hope this helps,
Ziga

Thanks Ziga,
i had already had a look at that package and its very good.
But, I guess what is different about what is used in the Verification
of electronic designs is the notion of randomized variables.
if you declared a randomized variable R1 and said it was constrained
such that
0=R1 256
Then you could generate values of R1 which would have successive
PSEUDO-RANDOM values between 0 and 255 inclusive.
If you introduced randomized variable R2, with the constraints:
R2 =0
R1*R2 512

Then you could generate R1,R2 pairs that satisfy the relations and
appear pseudo-random.

Some Electronic Design Automation constraint solvers might generate all
solutions before epeating. but this is not necessary.

The idea is that you electronic designs have a huge state space to test
and so cannot be exaustively tested. If you write a deterministic test
then you are directly loading your test with bias about how you think
the design works or should be tested. With constrained random
generation you work the other way by trying to constrain test segments
to create valid tests but due to the randomness involved, the tests
generated may exercise the design in valid ways that a deterministic
test writer would not have thought of.
The method does work in practice. I'd just like to know if my favourite
language might be changing to have this capability.

- Pad.

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Re: logging error with RotatingFileHandler

2006-07-02 Thread Vinay Sajip


flupke wrote:

  - The rename fails for some reason.

I would dig a little deeper to find out what the reason is. After all,
on the face of it, there's no obvious reason it should fail. The
permission denied indicates perhaps that some other process or thread
is keeping that file open?

I've fixed (AFAICT) both the crash at shutdown and the buggy exception
handling, in the Python subversion repository. You can download the
latest from here and try it.

http://svn.python.org/view/python/trunk/Lib/logging/

Regards,

Vinay Sajip

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RE: Dictionary .keys() and .values() should return a set [with Python3000 in mind]

2006-07-02 Thread Delaney, Timothy (Tim)

[EMAIL PROTECTED] wrote:

 This has been bothering me for a while. Just want to find out if it
 just me or perhaps others have thought of this too: Why shouldn't the
 keyset of a dictionary be represented as a set instead of a list?

There has been much discussion of this on the Python-3000 mailing list.
Suggestings included making keys(), etc return an iterator, and getting
rid of iterkeys(), etc.

The eventual consensus was that keys(), etc should return views on the
dictionary. These views would be re-iterable and will have basically the
same behaviour as the lists returned from keys(), etc. However, such a
view could have O(1) __contains__ behaviour, and would not incur the
overhead of creating a list and populating it - they would be backed by
the dictionary. Of course, this introduces the issue of concurrent
modification, but you can always get an independent copy by calling
list(dict.keys()).

Tim Delaney
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Re: wanted: framework for creating nice step by step graphical visualisations of running Python code

2006-07-02 Thread Claudio Grondi

[EMAIL PROTECTED] wrote:
 I remember Gato:
 http://gato.sourceforge.net/
 It animates only algorithms on graphs, but it seems a starting point,
 and it works.
 
 I vaguely remember another system, but probably not very good.
 
 Bye,
 bearophile
 
Yes, I have noticed Gato already before, but was not able to find my way 
into it - I am missing a kind of tutorial explaining what it is all 
about - the description of available classes or demos don't tell me much 
about it, so I have no idea how to start - is there any tutorial out 
there explaining it from the very beginning what is it for, how it does 
it and why?
By the way: it seems to be very slow on my 3 GHz Pentium 4 system ...

Any other hints?

Claudio
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Re: classes and interfaces

2006-07-02 Thread Rene Pijlman

[EMAIL PROTECTED]:
In python , how to implement interface like the above? 

Interfaces are lacking in Python, but an even more generic proposal is on
its way:
http://www.artima.com/weblogs/viewpost.jsp?thread=155123

In the mean time, interfaces have already been implemented in Zope 3:
http://www.zope.org/Products/ZopeInterface

-- 
René Pijlman

To find out what you can do with interfaces, see the interface interface,
IInterface in the IInterface module.
- Comment in Zope's Interface/__init__.py
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Re: classes and interfaces

2006-07-02 Thread Rene Pijlman

Bruno Desthuilliers:
Java interfaces are a workaround

Troll alert.
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python function defs/declarations

hi..

the docs state that the following is valid...

def foo():
 i = 2
 print i = i

print hello
foo()


is there a way for me to do this..

print hello
foo()

def foo():
 i = 2
 print i = i

ie, to use 'foo' prior to the declaration of 'foo'

thanks

-bruce

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Time out question

2006-07-02 Thread DarkBlue

My application makes several connections to
a remote database server via tcp/ip.
Usually all is fine,but occasionally the server is
down or the internet does not work and then there is
the 30 sec to several minutes timeout wait for the
tcp to give up.
Is there anything I can do without using 
threads,sockets,twisted etc. to have following :

pseudocode :

 try for 10 seconds
   if database.connected :
do your remote thing
 except raise after 10 seconds
   abort any connection attempt
   do something else 


Thanks
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Re: python function defs/declarations

bruce [EMAIL PROTECTED] wrote:

 hi..
 
 the docs state that the following is valid...
 
 def foo():
  i = 2
  print i = i
 
 print hello
 foo()
 
 
 is there a way for me to do this..
 
 print hello
 foo()
 
 def foo():
  i = 2
  print i = i
 
 ie, to use 'foo' prior to the declaration of 'foo'

There are no declarations in Python.  def is an executable statement:
when executes it binds a new function object to the given name.

So, your request is like asking to do, say:

print hello
print wap

wap = world

At the time you use name wap, nothing is bound to it; the fact that
something would later be bound to it (if the binding statement, here an
assignment but that's exactly as much of an executable statement as a
def!) is pretty clearly irrelevant.  Having a clear idea about these
issues is why it's important to remember the distinction between
executable statements (including def, class, assignments, ...) and
declarations (which Python does not have).

You can probably wrap your code in a function, and call it at the end:

def main():
  print hello
  foo()

def foo(): ...whatever...

main()


By the time the body of main executes, def foo has already executed,
so global name foo is happily bound and everything works fine.

Wrapping most substantial code inside functions is VERY advisable anyway
-- just put just about all the code you'd like to have at module top
level (except for def, class and assignments to module constants) into
a function (conventionally named main) and call that function at the
very end of the module (ideally within an if __name__=='__main__:
guard, but that's a different issue!).


Alex
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Re: Time out question

DarkBlue [EMAIL PROTECTED] wrote:

 My application makes several connections to
 a remote database server via tcp/ip.
 Usually all is fine,but occasionally the server is
 down or the internet does not work and then there is
 the 30 sec to several minutes timeout wait for the
 tcp to give up.
 Is there anything I can do without using 
 threads,sockets,twisted etc. to have following :
 
 pseudocode :
 
  try for 10 seconds
if database.connected :
 do your remote thing
  except raise after 10 seconds
abort any connection attempt
do something else 

Sure, see function setdefaulttimeout in module socket.  Just call it as
you wish before trying the DB connection and catch the resulting
exception.


Alex
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Re: xpath question

bruce wrote:
 simon..

 you may not.. but lot's of people use python and xpath for html/xml
 functionality.. check google python xpath...

 later..

...
  i have a situation where i have something like:
   /html/table//[EMAIL PROTECTED]'foo']
 
  is it possible to do soomething like [EMAIL PROTECTED]/fo/] so i'd match 
  the class
  attribute with fo
 


So I did some checking, starting with the google search you suggested,
and I found out that lxml, 4Suite, and Amara (which is apparently based
on 4Suite somehow) all seem to be capable of doing what you're talking
about.  I don't know how to do it with lxml, but I bet the people on
the lxml mailing list would be happy to explain it to you.  As for
Amara and 4Suite I think it might be as simple as saying Match(your
regex here in python re module form) in your Xpath statement..


In the meantime, you could just use Xpath to extract a superset of the
elements you're interested in and then filter them with a re.Match
object.


I avoid xml if I can help it...   My new favorite HTML editor, however,
is python and ElementTree...

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Re: xpath question

2006-07-02 Thread uche . ogbuji

bruce wrote:
 is there anyone with XPath expertise here? i'm trying to figure out if
 there's a way to use regex expressions with an xpath query? i've seen
 references to the ability to use regex and xpath/xml, but i'm not sure how
 to do it...

 i have a situation where i have something like:
  /html/table//[EMAIL PROTECTED]'foo']

 is it possible to do soomething like [EMAIL PROTECTED]/fo/] so i'd match the 
 class
 attribute with fo

 i'm trying to parse HTML/Web docs...

4Suite [1] supports regex in XPath using the EXSLT community standard's
regex module [2].  It would be something like:

[re:match(@class, 'fo.*']

With the re prefix set as required by the EXSLT module.

[1] http://4Suite.org
[2] http://www.exslt.org/regexp/

--
Uche Ogbuji   Fourthought, Inc.
http://uche.ogbuji.nethttp://fourthought.com
http://copia.ogbuji.net   http://4Suite.org
Articles: http://uche.ogbuji.net/tech/publications/

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Re: beautifulsoup .vs tidy

2006-07-02 Thread uche . ogbuji

bruce wrote:
 hi paddy...

 that's exactly what i'm trying to accomplish... i've used tidy, but it seems
 to still generate warnings...

  initFile - tidy -cleanFile - perl app (using xpath/livxml)

 the xpath/linxml functions in the perl app complain regarding the file. my
 thought is that tidy isn't cleaning enough, or that the perl xpath/libxml
 functions are too strict!

 which is why i decided to see if anyone on the python side has
 experienced/solved this problem..

FWIW here's my usual approach:

http://copia.ogbuji.net/blog/2005-07-22/Beyond_HTM

Personally, I avoid Tidy.  I've too often seen it crash or hang on
really bad HTML.  TagSoup seems to be built like a tank.  I've also
never seen BeautifulSoup choke, but I don't use it as much as TagSoup.

--
Uche Ogbuji   Fourthought, Inc.
http://uche.ogbuji.nethttp://fourthought.com
http://copia.ogbuji.net   http://4Suite.org
Articles: http://uche.ogbuji.net/tech/publications/

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Re: Amara: Where's my attribute?

2006-07-02 Thread uche . ogbuji

AdSR wrote:
 Hi,

 I'm having a problem with the Amara toolkit. Try this:

  from amara import binderytools
  raw = 'pq:test xmlns=http://example.com/namespace; 
  xmlns:pq=http://pq.com/ns2/'
  rwd = binderytools.bind_string(raw)
  print rwd.xml()
 ?xml version=1.0 encoding=UTF-8?
 pq:test xmlns:pq=http://pq.com/ns2/

 What happened to the xmlns attribute? Does anyone know a solution to
 this? The only workaround I found is to:

  rwd.test.xml_set_attribute(u'xmlns', u'http://example.com/namespace')
 u'xmlns'
  print rwd.xml()
 ?xml version=1.0 encoding=UTF-8?
 pq:test xmlns:pq=http://pq.com/ns2;
 xmlns=http://example.com/namespace/

 but it only helps if you know what to patch.

 My setup:

 Python 2.4.3
 4Suite 1.0b3
 Amara 1.0

 I see that people have reported similar problems with other XML
 toolkits, so I guess this is a general namespace ugliness.

What is the actual problem you're trying to solve?  If you just want to
force a namespace declaration in output (this is sually to support
QNames in content) the most well-known XML hack is to create a dummy
attribute with the needed prefix and namespace.  But this does not work
when you're trying to force a default namespace declaration.  Then
again, you generally can't use QNames in content with a default
namespace declaration.  So my guess is that you somehow got way off the
rails in your problem-solving, and you'll need to provide mre
background if you want help.

BTW, I recommend upgrading to Amara 1.1.7.  That branch will soon be
1.2, and I consider it more mature than 1.0 at this point.  The API's
also easier:

 import amara
 rwd = amara.parse('pq:test xmlns=http://example.com/namespace; 
 xmlns:pq=http://pq.com/ns2/')


--
Uche Ogbuji   Fourthought, Inc.
http://uche.ogbuji.nethttp://fourthought.com
http://copia.ogbuji.net   http://4Suite.org
Articles: http://uche.ogbuji.net/tech/publications/

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Turning a callback function into a generator

2006-07-02 Thread Kirk McDonald

Let's say I have a function that takes a callback function as a 
parameter, and uses it to describe an iteration:

def func(callback):
 for i in [1, 2, 3, 4, 5]:
 callback(i)

For the sake of argument, assume the iteration is something more 
interesting than this which relies on the callback mechanism. The 
function is an existing interface, and I cannot change it.

I want to somehow, in some way, provide an iteration interface to this 
function. Thoughts?

-Kirk McDonald
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how to stop python...

hi...

perl has the concept of die. does python have anything similar. how can a
python app be stopped?

the docs refer to a sys.stop.. but i can't find anything else... am i
missing something...

thanks

-bruce

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Re: how to stop python...

2006-07-02 Thread Tim Peters

[bruce]
 perl has the concept of die. does python have anything similar. how can a
 python app be stopped?

 the docs refer to a sys.stop.

Python docs?  Doubt it ;-)

 but i can't find anything else... am i missing something...

 import sys
 print sys.exit.__doc__
exit([status])

Exit the interpreter by raising SystemExit(status).
If the status is omitted or None, it defaults to zero (i.e., success).
If the status is numeric, it will be used as the system exit status.
If it is another kind of object, it will be printed and the system
exit status will be one (i.e., failure).



Of course there's nothing to stop you from catching SystemExit either
-- it's just another exception, but one that happens to shut down the
interpreter in the specified way if it isn't caught  handled.
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Re: how to stop python...

bruce [EMAIL PROTECTED] wrote:

 hi...
 
 perl has the concept of die. does python have anything similar. how can a
 python app be stopped?
 
 the docs refer to a sys.stop.. but i can't find anything else... am i
 missing something...

import sys

sys.exit()


Alex
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Re: how to stop python...

bruce wrote:
 hi...

 perl has the concept of die. does python have anything similar. how can a
 python app be stopped?

 the docs refer to a sys.stop.. but i can't find anything else... am i
 missing something...

 thanks

 -bruce

What you want is sys.exit()
See: http://docs.python.org/lib/module-sys.html

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Re: Dictionary .keys() and .values() should return a set [with Python3000 in mind]

2006-07-02 Thread Paul Rubin

Delaney, Timothy (Tim) [EMAIL PROTECTED] writes:
 The eventual consensus was that keys(), etc should return views on the
 dictionary. These views would be re-iterable and will have basically the
 same behaviour as the lists returned from keys(), etc. However, such a
 view could have O(1) __contains__ behaviour, and would not incur the
 overhead of creating a list and populating it - they would be backed by
 the dictionary. Of course, this introduces the issue of concurrent
 modification, but you can always get an independent copy by calling
 list(dict.keys()).

Wait a sec, you're saying

  k0 = d.keys()
  d['whee'] = 'parrot'# this can change k0???

That sounds broken.
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RE: Dictionary .keys() and .values() should return a set [withPython3000 in mind]

2006-07-02 Thread Delaney, Timothy (Tim)

Paul Rubin wrote:

 Delaney, Timothy (Tim) [EMAIL PROTECTED] writes:
 The eventual consensus was that keys(), etc should return views on
 the dictionary. These views would be re-iterable and will have
 basically the same behaviour as the lists returned from keys(), etc.
 However, such a view could have O(1) __contains__ behaviour, and
 would not incur the overhead of creating a list and populating it -
 they would be backed by the dictionary. Of course, this introduces
 the issue of concurrent modification, but you can always get an
 independent copy by calling list(dict.keys()).
 
 Wait a sec, you're saying
 
   k0 = d.keys()
   d['whee'] = 'parrot'# this can change k0???
 
 That sounds broken.

That's the problem with views. You either take a snapshot of the current
state, or you deal with the backing store changing. Java's solution is
to raise a ConcurrentModificationException when it determines this has
happened (with lots of weasel words about no guarantees).

If you want an independent data set, you have to take a snapshot. For
the above, that's doing:

k0 = list(d.keys())

or

k0 = set(d.keys())

depending on what behaviour you want.

Tim Delaney
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Re: how to stop python...

2006-07-02 Thread Paul McGuire

bruce [EMAIL PROTECTED] wrote in message
news:[EMAIL PROTECTED]
 hi...

 perl has the concept of die. does python have anything similar. how can
a
 python app be stopped?

 the docs refer to a sys.stop.. but i can't find anything else... am i
 missing something...

 thanks

 -bruce

(From the interactive Python prompt:)

import sys
dir(sys)
['__displayhook__', '__doc__', '__excepthook__', '__name__', '__stderr__',
'__st
din__', '__stdout__', '_getframe', 'api_version', 'argv',
'builtin_module_names'
, 'byteorder', 'call_tracing', 'callstats', 'copyright', 'displayhook',
'dllhand
le', 'exc_clear', 'exc_info', 'exc_type', 'excepthook', 'exec_prefix',
'executab
le', 'exit', 'getcheckinterval', 'getdefaultencoding',
'getfilesystemencoding',
'getrecursionlimit', 'getrefcount', 'getwindowsversion', 'hexversion',
'maxint',
 'maxunicode', 'meta_path', 'modules', 'path', 'path_hooks',
'path_importer_cach
e', 'platform', 'prefix', 'ps1', 'ps2', 'setcheckinterval', 'setprofile',
'setre
cursionlimit', 'settrace', 'stderr', 'stdin', 'stdout', 'version',
'version_info
', 'warnoptions', 'winver']

(Hmmm, no mention of stop, but perhaps exit???)

help(sys.exit)

Help on built-in function exit in module sys:

exit(...)
exit([status])

Exit the interpreter by raising SystemExit(status).
If the status is omitted or None, it defaults to zero (i.e., success).
If the status is numeric, it will be used as the system exit status.
If it is another kind of object, it will be printed and the system
exit status will be one (i.e., failure).


sys.exit()

Voila!

and now this from the What's new in Python 2.5:
---
In the interactive interpreter, quit and exit have long been strings so that
new users get a somewhat helpful message when they try to quit:

 quit
'Use Ctrl-D (i.e. EOF) to exit.'
In Python 2.5, quit and exit are now objects that still produce string
representations of themselves, but are also callable. Newbies who try quit()
or exit() will now exit the interpreter as they expect. (Implemented by
Georg Brandl.)

---

So from the  Python prompt, instead of ^D to exit, one can type quit()
or exit().  Or if sys has been imported, sys.exit().  From within a script,
one can call sys.exit().

-- Paul




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Re: Dictionary .keys() and .values() should return a set [withPython3000 in mind]

2006-07-02 Thread Paul Rubin

Delaney, Timothy (Tim) [EMAIL PROTECTED] writes:
 If you want an independent data set, you have to take a snapshot. For
 the above, that's doing:
 
 k0 = list(d.keys())

I don't understand.  Why have .keys() at all, if it doesn't get you
an independent data set?  If all you want is to iterate through the
dict, you can already do that:

  for k in d: 
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[ python-Bugs-1333982 ] Bugs of the new AST compiler

Bugs item #1333982, was opened at 2005-10-21 10:08
Message generated for change (Comment added) made by arigo
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including the initial issue submission, for this request,
not just the latest update.
Category: Parser/Compiler
Group: AST
Status: Open
Resolution: None
Priority: 7
Submitted By: Armin Rigo (arigo)
Assigned to: Jeremy Hylton (jhylton)
Summary: Bugs of the new AST compiler

Initial Comment:
The newly merged AST branch is likely to expose
a number of small problems before it stabilizes,
so here is a tentative bug tracker entry to
collect such small problems.


--

Comment By: Armin Rigo (arigo)
Date: 2006-07-02 11:29

Message:
Logged In: YES 
user_id=4771

Attached a patch for the LOAD_CONST POP_TOP optimization
(modified from Georg Brandl on python-dev).

--

Comment By: Michael Hudson (mwh)
Date: 2006-04-11 09:41

Message:
Logged In: YES 
user_id=6656

Good morning Armin!

I've reported that bug already: http://python.org/sf/1441486
There's a patch which purports to fix it: http://python.org/sf/1446922
but I haven't gotten around to testing it.

(this is running the pypy/module/array tests or something, isn't it?)

--

Comment By: Armin Rigo (arigo)
Date: 2006-04-11 08:45

Message:
Logged In: YES 
user_id=4771

Another one: the literal -2147483648 (i.e. the value of
-sys.maxint-1) gives a long in 2.5, but an int in = 2.4.

--

Comment By: Neal Norwitz (nnorwitz)
Date: 2006-04-03 07:30

Message:
Logged In: YES 
user_id=33168

The tuple store problem is fixed.  The only outstanding item
is the LOAD_CONST/POP_TOP.  I will fix that soon.

--

Comment By: Neal Norwitz (nnorwitz)
Date: 2006-02-18 06:56

Message:
Logged In: YES 
user_id=33168

Jeremy, there's no need to read anything before my last
comment at 2005-12-17 23:10.  The last two by Armin,
Michael, then my last comment are the only important ones. 
Everything that occurred before my 2005-12-17 comment was
taken care of AFAIK.

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Comment By: Armin Rigo (arigo)
Date: 2006-02-12 21:54

Message:
Logged In: YES 
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Subscripting is generally a bit sloppy: e.g. the AST model has
no way to distinguish between a single value and a one-element
tuple value!  See:

 d = {}
 d[1,] = 6
 d
{1: 6}# !

I suggest we fix the model to turn the 'subs' of the 'Subscript' node
from a list of nodes to a single, mandatory 'sub' node.  If tupling is
necessary, it can be explicitly represented with a 'sub' containing a
'Tuple' node.

--

Comment By: Michael Hudson (mwh)
Date: 2006-02-09 15:02

Message:
Logged In: YES 
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We found another one.  Something is wrong in the compilation of augmented 
assignment to subscriptions containing tuples; running this code:

class C:
def __setitem__(self, i, v):
print i, v
def __getitem__(self, i):
print i
return 0

c = C()
c[4,5] += 1

gives a spurious exception:

Traceback (most recent call last):
  File stdin, line 1, in module
TypeError: object does not support item assignment

By contrast, c[(4,5)] += 1 works fine.



--

Comment By: Neal Norwitz (nnorwitz)
Date: 2005-12-18 07:10

Message:
Logged In: YES 
user_id=33168

EXTENDED_ARG problem was fixed a while ago.
The assert/pass problem was fixed with: 41756.

That leaves the LOAD_CONST/POP_TOP optimization that was
lost and one compiler warning: marshal_write_mod() not being
used.

--

Comment By: Michael Hudson (mwh)
Date: 2005-12-11 00:41

Message:
Logged In: YES 
user_id=6656

You have to include those lines in a source file.  It still crashes for me.

--

Comment By: Brett Cannon (bcannon)
Date: 2005-12-10 23:44

Message:
Logged In: YES 
user_id=357491

I just checked Armin's problem code on rev. 41638 and it
worked for me in the interpreter.  You still having
problems, Armin?

--

Comment By: Armin Rigo (arigo)
Date: 2005-12-04 10:30

Message:
Logged In: YES 
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At rev 41584, the following code snippet triggers an assert
if --with-pydebug is enabled:
Python/compile.c:3843: assemble_lnotab: Assertion 'd_lineno = 0' failed

---
assert 1, ([s for s in x] +

[ python-Bugs-1515829 ] Exponential behavior in regular expression

Bugs item #1515829, was opened at 2006-07-02 08:26
Message generated for change (Tracker Item Submitted) made by Item Submitter
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including the initial issue submission, for this request,
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Category: Regular Expressions
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Submitted By: Erik Demaine (edemaine)
Assigned to: Gustavo Niemeyer (niemeyer)
Summary: Exponential behavior in regular expression

Initial Comment:
're' seems to have serious performance trouble with
nested Kleene stars in the regular expression, if the
matched text is fairly long.  Attached is an example,
naturally arising in some LaTeX parsing [admittedly not
the only way to do it], along with a text generator
parameterized by a repetition count n.  Here is simple
timing data on a Pentium 4 1.5GHz with 1.5GB RAM as a
function of n:

[...]
n=4: 0:00:00.015000
n=5: 0:00:00.032000
n=6: 0:00:00.14
n=7: 0:00:00.594000
n=8: 0:00:02.203000
n=9: 0:00:08.859000
n=10: 0:00:39.641000
n=11: 0:02:44.172000
n=12: 0:10:23.50

This seems far slower than it should be, but I don't
know the algorithm used by 're'.  Is this behavior
expected?  If so, should it be optimized away by
changing the algorithm?

The generated text consists of a few lines of preamble,
then a variable number n of copies of a partiuclar
line, followed by a few lines of postscript.  The first
line of the postscript causes the regular expression
*not* to match, and 're' spends a long time to find
that out.  Removing that line from the postscript, and
causing the regular expression to match, makes the
program run instantly.

I get the same behavior on Python 2.4 and 2.5b1, on
Windows and Linux, and with re.sub and re.search.

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[ python-Bugs-1515839 ] socket timeout inheritance on accept

Bugs item #1515839, was opened at 2006-07-02 16:05
Message generated for change (Tracker Item Submitted) made by Item Submitter
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including the initial issue submission, for this request,
not just the latest update.
Category: Python Library
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Submitted By: Jari Kirma (kirma)
Assigned to: Nobody/Anonymous (nobody)
Summary: socket timeout inheritance on accept

Initial Comment:
Socket objects returned by socket.accept() get their
blocking and timeout setting(s) from
socket.defaulttimeout. This can be in conflict with
reality of the (non-)blocking mode of actual OS-level
socket they use. For instance, FreeBSD sockets inherit
their socket options from the parent socket on
accept(2) system call, and thus a socket object with
defined socket timeout and default defaulttimeout
returns a socket object that seems to be blocking,
non-timeout socket, but the underlying OS socket is
actually in nonblocking mode, which can cause read/recv
and write/send operations to behave unexpectedly. Even
worse, POSIX/SUSv3 doesn't explicitly require socket
option inheritance
(http://www.opengroup.org/onlinepubs/009695399/functions/accept.html).
  

The socket library should explicitly set the socket
timeout mode (either to defaulttimeout, or with
accompanying documentation, inherit the value from
socket object passed to accept()) and modify the OS
socket options accordingly.

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[ python-Bugs-1515839 ] socket timeout inheritance on accept

Bugs item #1515839, was opened at 2006-07-02 16:05
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Category: Python Library
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Submitted By: Jari Kirma (kirma)
Assigned to: Nobody/Anonymous (nobody)
Summary: socket timeout inheritance on accept

Initial Comment:
Socket objects returned by socket.accept() get their
blocking and timeout setting(s) from
socket.defaulttimeout. This can be in conflict with
reality of the (non-)blocking mode of actual OS-level
socket they use. For instance, FreeBSD sockets inherit
their socket options from the parent socket on
accept(2) system call, and thus a socket object with
defined socket timeout and default defaulttimeout
returns a socket object that seems to be blocking,
non-timeout socket, but the underlying OS socket is
actually in nonblocking mode, which can cause read/recv
and write/send operations to behave unexpectedly. Even
worse, POSIX/SUSv3 doesn't explicitly require socket
option inheritance
(http://www.opengroup.org/onlinepubs/009695399/functions/accept.html).
  

The socket library should explicitly set the socket
timeout mode (either to defaulttimeout, or with
accompanying documentation, inherit the value from
socket object passed to accept()) and modify the OS
socket options accordingly.

--

Comment By: Jari Kirma (kirma)
Date: 2006-07-02 16:23

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Making socket objects behave reliably can be achieved simply
by always calling internal_setblocking in init_sockobject of
socketmodule.c, but this causes overhead of one system call
on all socket creations. Alternatively one could call
internal_setblocking from sock_accept if parent socket has
timeouts/nonblocking mode enabled. This should work in under
all reasonable scenanarios and avoid system call overhead on
majority of cases.

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[ python-Bugs-1515932 ] 2.3.6.4 Mutable Sequence Types clarification

Bugs item #1515932, was opened at 2006-07-02 12:53
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Category: Documentation
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Alan (aisaac0)
Assigned to: Nobody/Anonymous (nobody)
Summary: 2.3.6.4 Mutable Sequence Types clarification

Initial Comment:
Documentation of Mutable Sequence Types
at http://docs.python.org/lib/typesseq-mutable.html
has the following language:

s[i:j] = t  slice of s from i to j is replaced by t 
...
s[i:j:k] = t the elements of s[i:j:k] are replaced by
those of t  (1)

The asymmetry is misleading (e.g., one might think that
in the first case t could be a single number that would
be assigned to all the elements, particularly since the
footnote is omitted).

Therefore I propose the first case become:

s[i:j] = t   the elements of the slice of s from i to j
are replaced by those of t  (1)

The following alternative would be even more parallel
and also acceptable:

s[i:j] = t  the elements of s[i:j] are replaced by
those of t  (1)

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[ python-Bugs-1513646 ] os.access reports incorrect write permissions in Windows

Bugs item #1513646, was opened at 2006-06-28 00:01
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Category: Windows
Group: Python 2.5
Status: Closed
Resolution: Fixed
Priority: 7
Submitted By: Yi S. Ding (yi_ding)
Assigned to: Martin v. LÃ¶wis (loewis)
Summary: os.access reports incorrect write permissions in Windows

Initial Comment:
Platform: Python 2.5b1 Windows XP

Bug:
os.access will report that a user doesn't have write
permissions to a file or directory when the user
actually does.

Reproducibility: always

This is being run on an administrator account.
 import os
 os.access(C:\\, os.W_OK)
False
 os.access(C:\\test.txt, os.W_OK)
False

I have also checked that Python can indeed write to the
file.

--

Comment By: Martin v. LÃ¶wis (loewis)
Date: 2006-07-02 20:45

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Thanks for the report and the patch, committed as r47198 (I
moved the test in a separate class, though).

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Comment By: Yi S. Ding (yi_ding)
Date: 2006-07-01 01:12

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Cool.  I added the new patch with the test case.

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Comment By: Neal Norwitz (nnorwitz)
Date: 2006-06-30 09:12

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Your change looks correct, but I would really like a test
case to fix this problem.  I don't have access to a Windows
box, so I can't verify the test fails before this patch and
succeeds with it.  Can you create a test case too?  The best
place to add the test would be Lib/test/test_posix.py.  Thanks!

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Comment By: Yi S. Ding (yi_ding)
Date: 2006-06-29 21:56

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Yeah, it's only 2.5, and only 2.5b1.  Basically, there's a
double ampersand used instead of a single ampersand in
posixmodule.c.  I've attached the patch.

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Comment By: Neal Norwitz (nnorwitz)
Date: 2006-06-28 07:28

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Does this problem only occur with 2.5 or is it also present
in 2.4?

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[ python-Bugs-1514617 ] evaluated code filename changed to module instead of ?

Bugs item #1514617, was opened at 2006-06-29 16:07
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Category: Python Interpreter Core
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Submitted By: James Y Knight (foom)
Assigned to: Nobody/Anonymous (nobody)
Summary: evaluated code filename changed to module instead of ?

Initial Comment:
It seems as though the default filename for evaluated changed from ? to 
module. Was this intentional? (it's causing some test failures for me. 
The tests are correctable of course, but it doesn't seem to be an obvious 
improvement in behavior, so if it wasn't intentional, perhaps it should be 
changed back.)

Python 2.3.5 (#1, Mar 20 2005, 20:38:20) 
[GCC 3.3 20030304 (Apple Computer, Inc. build 1809)] on darwin

 eval(0/0)
Traceback (most recent call last):
  File stdin, line 1, in ?
  File string, line 0, in ?


Python 2.5b1 (trunk:47096, Jun 25 2006, 23:18:21) 
[GCC 4.0.0 20041026 (Apple Computer, Inc. build 4061)] on darwin

 eval(0/0)
Traceback (most recent call last):
  File stdin, line 1, in module
  File string, line 1, in module
ZeroDivisionError: integer division or modulo by zero


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Comment By: Jp Calderone (kuran)
Date: 2006-07-02 16:18

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Note that in the example James included, the code is /not/
in a module.

A clear improvement to me would be to say something like
repl or interactive prompt in the case James pasted and
the name of a module for the case of top-level code.

module is about as information-free as ?.


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Comment By: Collin Winter (collinwinter)
Date: 2006-07-01 14:26

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For me, this is indeed an obvious improvement in behaviour.
module is a much clearer indicator of where the code in
question is located; using ? could mean that it's anywhere.

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[ python-Bugs-1514617 ] evaluated code filename changed to module instead of ?

Bugs item #1514617, was opened at 2006-06-29 16:07
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Category: Python Interpreter Core
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Submitted By: James Y Knight (foom)
Assigned to: Nobody/Anonymous (nobody)
Summary: evaluated code filename changed to module instead of ?

Initial Comment:
It seems as though the default filename for evaluated changed from ? to 
module. Was this intentional? (it's causing some test failures for me. 
The tests are correctable of course, but it doesn't seem to be an obvious 
improvement in behavior, so if it wasn't intentional, perhaps it should be 
changed back.)

Python 2.3.5 (#1, Mar 20 2005, 20:38:20) 
[GCC 3.3 20030304 (Apple Computer, Inc. build 1809)] on darwin

 eval(0/0)
Traceback (most recent call last):
  File stdin, line 1, in ?
  File string, line 0, in ?


Python 2.5b1 (trunk:47096, Jun 25 2006, 23:18:21) 
[GCC 4.0.0 20041026 (Apple Computer, Inc. build 4061)] on darwin

 eval(0/0)
Traceback (most recent call last):
  File stdin, line 1, in module
  File string, line 1, in module
ZeroDivisionError: integer division or modulo by zero


--

Comment By: Jp Calderone (kuran)
Date: 2006-07-02 16:20

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Also see
https://sourceforge.net/tracker/?func=detailaid=1512007group_id=5470atid=305470
for a patch to revert to the old behavior.


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Comment By: Jp Calderone (kuran)
Date: 2006-07-02 16:18

Message:
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Note that in the example James included, the code is /not/
in a module.

A clear improvement to me would be to say something like
repl or interactive prompt in the case James pasted and
the name of a module for the case of top-level code.

module is about as information-free as ?.


--

Comment By: Collin Winter (collinwinter)
Date: 2006-07-01 14:26

Message:
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For me, this is indeed an obvious improvement in behaviour.
module is a much clearer indicator of where the code in
question is located; using ? could mean that it's anywhere.

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[ python-Bugs-1515998 ] bdist_msi fails (egg-info)

Bugs item #1515998, was opened at 2006-07-02 21:44
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Category: Distutils
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Submitted By: Paul Moore (pmoore)
Assigned to: Nobody/Anonymous (nobody)
Summary: bdist_msi fails (egg-info)

Initial Comment:
If I try to build a bdist_msi installer for a trivial
module, using Python 2.5b1, I get an error.

It looks like a problem with the interaction of the new
(in 2.5) egg-info stuff and the bdist_msi code - but I
have no further ideas.
Here is the setup.py

from distutils.core import setup
setup(
   name='test',
   version='1.0',
   py_modules=['test'],
)

And here is the build output:

python setup.py bdist_msi
running bdist_msi
running build
running build_py
creating build
creating build\lib
copying test.py - build\lib
installing to build\bdist.win32\msi
running install_lib
creating build\bdist.win32
creating build\bdist.win32\msi
creating build\bdist.win32\msi\Lib
creating build\bdist.win32\msi\Lib\site-packages
copying build\lib\test.py -
build\bdist.win32\msi\Lib\site-packages
running install_egg_info
Writing
build\bdist.win32\msi\Lib\site-packages\test-1.0-py2.5.egg-info
creating dist
Traceback (most recent call last):
 File setup.py, line 5, in module
   py_modules=['test'],
 File D:\Apps\Python25\Lib\distutils\core.py, line
151, in setup
   dist.run_commands()
 File D:\Apps\Python25\Lib\distutils\dist.py, line
974, in run_commands
   self.run_command(cmd)
 File D:\Apps\Python25\Lib\distutils\dist.py, line
994, in run_command
   cmd_obj.run()
 File
D:\Apps\Python25\Lib\distutils\command\bdist_msi.py,
line 235, in run
   self.add_files()
 File
D:\Apps\Python25\Lib\distutils\command\bdist_msi.py, line
263, in add_files
   key = dir.add_file(file)
 File D:\Apps\Python25\Lib\msilib\__init__.py, line
343, in add_file
   language, attributes, sequence)])
 File D:\Apps\Python25\Lib\msilib\__init__.py, line
115, in add_data
   raise MSIError(Could not insert +repr(values)+
into +table)
_msi.MSIError: Could not insert [(None, 'site_packages',
'TEST-1~1.EGG|test-1.0-py2.5.egg-info', 186L, None,
None, 512, 1)]
into File


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[ python-Bugs-1515829 ] Exponential behavior in regular expression

Bugs item #1515829, was opened at 2006-07-02 08:26
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Category: Regular Expressions
Group: Feature Request
Status: Closed
Resolution: Wont Fix
Priority: 5
Submitted By: Erik Demaine (edemaine)
Assigned to: Nobody/Anonymous (nobody)
Summary: Exponential behavior in regular expression

Initial Comment:
're' seems to have serious performance trouble with
nested Kleene stars in the regular expression, if the
matched text is fairly long.  Attached is an example,
naturally arising in some LaTeX parsing [admittedly not
the only way to do it], along with a text generator
parameterized by a repetition count n.  Here is simple
timing data on a Pentium 4 1.5GHz with 1.5GB RAM as a
function of n:

[...]
n=4: 0:00:00.015000
n=5: 0:00:00.032000
n=6: 0:00:00.14
n=7: 0:00:00.594000
n=8: 0:00:02.203000
n=9: 0:00:08.859000
n=10: 0:00:39.641000
n=11: 0:02:44.172000
n=12: 0:10:23.50

This seems far slower than it should be, but I don't
know the algorithm used by 're'.  Is this behavior
expected?  If so, should it be optimized away by
changing the algorithm?

The generated text consists of a few lines of preamble,
then a variable number n of copies of a partiuclar
line, followed by a few lines of postscript.  The first
line of the postscript causes the regular expression
*not* to match, and 're' spends a long time to find
that out.  Removing that line from the postscript, and
causing the regular expression to match, makes the
program run instantly.

I get the same behavior on Python 2.4 and 2.5b1, on
Windows and Linux, and with re.sub and re.search.

--

Comment By: Tim Peters (tim_one)
Date: 2006-07-02 17:40

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Since this isn't going to change, I'm closing this.

I don't know exactly what your regexp is intended to match,
but I expect this will help speed it enormously:  inside a
group, one of the alternatives is the negated character
class (NCC):

[^{}%]

One of the other alternatives starts with { and another
with %.  That's very good, because those three
alternatives are mutually exclusive based on just the
current character in the target string.

However, yet another alternative starts with a backslash,
and it's thus ambiguous whether the backslash should be
matched by that alternative or by the NCC.  Because this is
a backtracking engine, and the NCC is the first alternative,
it tries the NCC first and won't try the backslash
alternative unless it's impossible to find a match having
tried the NCC.  That can cause exponential-time
failing-match behavior all by itself.

If it's the case that a backslash in this context is
_always_ supposed to match the

\\.

alternative, then adding a backslash to the NCC removes the
ambiguity and greatly speeds (at least) failing matches:

[^{}%\\]

Then which alternative is supposed to match is entirely
determined by the current character in the target string, so
when backtracking on failure all other alternatives fail at
once, and backtracking continues with at worst insignificant
delay.

Adding a backslash to the inner NCC helps a little, but
adding one to the outer NCC too is very effective:

n=0: 0:00:00
n=1: 0:00:00
n=2: 0:00:00
...
n=97: 0:00:00
n=98: 0:00:00
n=99: 0:00:00

See Friedl's book for much more along these lines.

--

Comment By: Tim Peters (tim_one)
Date: 2006-07-02 09:13

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Yes, it's easy to provoke exponential-time behavior.  For a
simple example, the regexp

^((a+)*)*$

takes O(3**n) time to fail to match strings of the form

a*n + b

Python's matcher is a backtracking engine, much like Perl's,
and most other languages' non-POSIX re facilities.  There's
nary a DFA in sight ;-)  Jeffrey Friedl's thick O'Reilly
book Mastering Regular Expressions is mostly about the
pragmatics of using such engines efficiently:

http://regex.info/

Note that there's no current hope that this will change: 
because of gimmicks like backreferences, these aren't
CompSci's idea of regular expressions, and no thoroughly
efficient implementation technique is known.  For example,
this teensy regexp:

^(aa+)\\1+$

matches strings of a's whose length isn't prime, and finds a
non-trivial factor when the length is composite.  For
harder-to-solve but messier examples:

http://perl.plover.com/NPC/

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[ python-Bugs-1516068 ] Under OS X, compiling against local readline fails

Bugs item #1516068, was opened at 2006-07-02 17:42
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Category: Build
Group: Platform-specific
Status: Open
Resolution: None
Priority: 5
Submitted By: Nelson Arzola (narzola72)
Assigned to: Nobody/Anonymous (nobody)
Summary: Under OS X, compiling against local readline fails

Initial Comment:
I've installed a version of the GNU Readline (5.1) in a
local directory (/Volumes/DATA/dev/toolset/{include,lib}.

I'm compiling Python with:

CFLAGS=-I/Volumes/DATA/dev/toolset/include \
LDFLAGS=-L/Volumes/DATA/dev/toolset/lib \
./configure \
 --prefix=/Volues/DATA/dev/toolset/inst/python \
 --with-libs=-lexpat -lncurses -lreadline
make

I get the following error:

./Modules/readline.c:885: error: 'HISTORY_STATE'
undeclared (first use in this function)
./Modules/readline.c:885: error: 'state' undeclared
(first use in this function)
./Modules/readline.c:887: warning: assignment discards
qualifiers from pointer target type

When I look at the gcc command that was used to compile
Modules/readline.c, I see that my CFLAGS is not passed
to gcc and so the (broken) system readline is being used.

I can temporarily solve this problem with:

echo readline readline.c ${CFLAGS} ${LDFLAGS}
-lreadline -l termcap  Modules/Setup.local

before I call make.

What I can't understand is why the build process
correctly uses the local version of expat (2.0.0) that
is installed in the directories with readline, but not
readline?

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[ python-Bugs-1516068 ] Under OS X, compiling against local readline fails