python-dev Summary for 2004-09-16 through 2004-09-30

Brett C bac at OCF.Berkeley.EDU
Sun Oct 17 04:27:07 CEST 2004

python-dev Summary for 2004-09-16 through 2004-09-30
This is a summary of traffic on the `python-dev mailing list`_ from September 
16, 2004 through September 30, 2004.  It is intended to inform the wider Python 
community of on-going developments on the list.  To comment on anything 
mentioned here, just post to `comp.lang.python`_ (or email 
python-list at which is a gateway to the newsgroup) with a subject line 
mentioning what you are discussing. All python-dev members are interested in 
seeing ideas discussed by the community, so don't hesitate to take a stance on 
something.  And if all of this really interests you then get involved and join 

This is the forty-ninth summary written by Brett Cannon (Wow, my thesis gives 
an entire .5% speed-up on pystone at the moment; ain't that grand...).

To contact me, please send email to brett at ; I do not have the 
time to keep up on comp.lang.python and thus do not always catch follow-ups 
posted there.

All summaries are archived at .

Please note that this summary is written using reStructuredText_ which can be 
found at .  Any unfamiliar punctuation is 
probably markup for reST_ (otherwise it is probably regular expression syntax 
or a typo =); you can safely ignore it, although I suggest learning reST; it's 
simple and is accepted for `PEP markup`_ and gives some perks for the HTML 
output.  Also, because of the wonders of programs that like to reformat text, I 
cannot guarantee you will be able to run the text version of this summary 
through Docutils_ as-is unless it is from the `original text file`_.

.. _PEP Markup:

The in-development version of the documentation for Python can be found at and should be used when looking up any
documentation on new code; otherwise use the current documentation as found at .  PEPs (Python Enhancement Proposals) are located at .  To view files in the Python CVS online, go to .  Reported bugs and 
suggested patches can be found at the SourceForge_ project page.

The `Python Software Foundation`_ is the non-profit organization that holds the 
intellectual property for Python.  It also tries to forward the development and 
use of Python.  But the PSF_ cannot do this without donations.  You can make a 
donation at .  Every penny helps so even a 
small donation (you can donate through PayPal or by check) helps.

.. _python-dev:
.. _SourceForge:
.. _python-dev mailing list:
.. _comp.lang.python:
.. _Docutils:
.. _reST:
.. _reStructuredText:
.. _PSF:
.. _Python Software Foundation:

.. contents::

.. _last summary:
.. _original text file:

Summary Announcements
Wow.  This must have been the easiest summary I have ever done.  Why can't they 
all be like this?  I didn't even skip that much!

This summary also marks the first instance of having a contributing writer 
(ignoring the time when Raymond Hettinger was guest writer and wrote the whole 
summary himself).  So thanks to Michael Chermside for writing up those 
summaries.  And this is open to anyone, so if you feel that one of the skipped 
threads is worth summarizing and you catch it on the draft I send out of the 
Summary please mail them to me and it will probably get included.

Assume nothing when mutability is possible
Tim Peters discovered a new way to create an infinite list thanks to generator 
expressions.  But what really came out of this whole discussion came about when 
someone else came up with an example that exposed a bug in list.extend().

The first thing was that "you can't assume anything about a mutable object 
after potentially calling back into Python."  Basically you can't assume the 
state of any mutable object was not changed if you execute Python code from C. 
  While it might seem handy to store state while in a loop for instance, you 
can't count on things not changing by the time you get control back so you just 
have to do it the hard way and get state all over again.

Second was that you need to be careful when dealing with iterators.  If you 
mutate an iterator while iterating you don't have a guarantee it won't explode 
in your face.  Unless you explicitly support it, document it, and take care to 
protect against it then just don't assume you can mutate an iterator while 
using it.

Contributing threads:
   - `A cute new way to get an infinite loop 
   - `More data points 

The fewer licenses the better
The idea of copying some code from OpenSSH_ for better pty handling was 
proposed.  This was frowned upon since that becomes one more legal issue to 
keep track of.  Minimizing the licenses that Python must keep track of and make 
sure to comply with, no matter how friendly, is a good thing.

.. _OpenSSH:

Contributing threads:
   - `using openssh's pty code 

Trying to deal with the exception hierarchy in a backwards-friendly way
Nick Coghlan came up with the idea of having a tuple that contained all of the 
exceptions you normally would not want to catch in a blanket 'except' 
statement; KeyboardInterrupt, MemoryError, SystemExit, etc.).  This tuple was 
proposed to live in sys.special_exceptions with the intended usage of::

    pass # stuff...
  except sys.special_exceptions:
    raise # exceptions that you would not want to catch should keep propogating 
up the call chain
    pass # if you reach here the exception should not be a *huge* deal

Obviously the best solution is to just clean up the exception hierarchy, but 
that breaks backwards-compatibility.  But this idea seemed to lose steam.

Contributing threads:
   - `Proposing a sys.special_exceptions tuple 

Built on beer!
by Michael Chermside

In this short thread Guido admits that Python *is* really built on
beer: "'s true! During the early days, when hacking on Python,
I often lived on stroopwafels and beer."

Contributing threads:
    - `built on beer? 

Docs still available in gzip format
by Michael Chermside

Fred Drake suggested that we stop providing the Python
documentation in gzip format. We offered the zip and bzip2 formats which have
unique advantages (bzip2 compresses better and zip has a directory built in so
individual files can be extracted) over gzip and he wanted to reduce the number
of different formats offered. However, there was much dissention, so the
final decision was to retain the format.

Contributing threads:
    - `Planning to drop gzip compression for future releases. 

Making running stdlib modules as scripts that much easier
Nick Coghlan contributed a patch for a new command-line option, ``-m``, that 
will search sys.path for a module of that name and execute it as a 
``__main__``.  This can be really handy for things such as checking the 
docstrings of a module (``python -m pydoc heapq``) and such.

Currently, though, it only for top-level modules in sys.path and thus ignores 
packages.  If you want that functionality there is a recipe by Nick on the 
Python Cookbook at .  There is also 
discussions going on python-dev about how to possibly add this in the future.

Contributing threads:
   - `Running a module as a script 

Skipped Threads

- Decimal, copyright and license
- Noam's open regex requests
- Socket/Asyncore bug needs attention
- open('/dev/null').read() -> MemoryError
- Finding the module from PyTypeObject?
- Odd compile errors for bad genexps

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