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python-dev Summary for 2005-04-01 through 2005-04-15

[The HTML version of this Summary is available at
http://www.python.org/dev/summary/2005-04-01_2005-04-15.html]



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Summary Announcements
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---------------------------
New python-dev summary team
---------------------------

This summary marks the first by the team of Steve Bethard, Tim Lesher,
and Tony Meyer.  We're trying a collaborative approach to the
summaries: each fortnight, we'll be getting together in a virtual
smoke-filled back room to divide up the interesting threads.  Then
we'll stitch together the summaries in roughly the same form as you've
seen in the past. We'll mark each editor's entries with his initials.

Thanks to Brett Cannon for sixty-one excellent python-dev summaries.
Also, thanks for providing scripts to help get the new summaries off
the ground! We're looking forward to the contributions you'll make to
the Python core, now that the summaries aren't taking up all your
time.

[TDL]

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Summaries
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-----------------------
Acceptable diff formats
-----------------------

Nick Coghlan asked if context diffs are still favoured for patches.
Historically, context diffs were preferred, but it appears that
unified diffs are the today's choice.  Raymond Hettinger made the
sensible suggestion that whichever is most informative for the
particular patch should be used, and Bob Ippolito pointed out that if
CVS is replaced with subversion, unified diffs will have better
support.  The `patch submission guidelines`_ will be updated at some
point to reflect the preference for unified diffs, although if your
diff program doesn't support '-u', then context diffs are ok - plain
patches are, of course, not.

Contributing threads:

- `Unified or context diffs?
<http://mail.python.org/pipermail/python-dev/2005-April/052657.html>`__

..=2E _patch submission guidelines: http://www.python.org/patches/

[TAM]


---------------
Developers List
---------------

Raymond Hettinger has started a `project to track developers`_ and the
(tracker and commit) privileges they have, and who gave them the
privileges, and why (for example, was it for a one-shot
project). Removing inactive developers should improve clarity,
institutional memory, security, and makes everything tidier.  Raymond
has begun contacting recently inactive developers to check whether
they still require the privileges they have.

Contributing threads:

- `Developer list update
<http://mail.python.org/pipermail/python-dev/2005-April/052540.html>`__

..=2E _project to track developers:
http://cvs.sourceforge.net/viewcvs.py/*checkout*/python/python/dist/src/Mis=
c/developers.txt

[TAM]

----------------------
Right Operator Methods
----------------------

Greg Ewing explored an issue with new-style classes that define only
right operator methods (__radd__, __rmul__, etc.)  Instances of such a
class cannot be added/multiplied/etc. together as Python raises a
TypeError. Armin Rigo explained the rule: if the instances on both
sides of an operator are of the same class, only the non-reversed
method is ever called. Armin also explained that an __add__ or __mul__
method that returns NotImplemented may be called twice when Python
attempts to differentiate between numeric and sequence operations.

Contributing threads:

- `New style classes and operator methods
<http://mail.python.org/pipermail/python-dev/2005-April/052577.html>`__

[SJB]

------------------------------------------
Hierarchical groups in regular expressions
------------------------------------------

Chris Ottrey demoed his `pyre2 project`_ that can extract a hierarchy
of strings when nested groups match in a regular expression.  The
current re module (in the stdlib) only matches the last occurrence of
a group in the string, throwing away any preceding matches. People
discussed some of pyre2's proposed API, with the main suggestion being
to extend the API to support unnamed (positional) groups in addition
to named groups.

Though a number of people expressed interest in the idea, it was not
clear whether the functionality should be included in the standard
library. However, most agreed that if it was included, it should be
integrated with the existing re module. Gustavo Niemeyer offered to
perform this integration if an API could be agreed upon. Further
discussion was moved to the pyre2 `development wiki`_ and `mailing
list`_.

Contributing threads:

- `hierarchicial named groups extension to the re library
<http://mail.python.org/pipermail/python-dev/2005-April/052508.html>`__

..=2E _pyre2 project: http://pyre2.sourceforge.net/

..=2E _development wiki: http://py.redsoft.be/pyre2/wiki/

..=2E _mailing list:
http://lists.sourceforge.net/lists/listinfo/pyre2-devel

[SJB]

-------------------------------
Security capabilities in Python
-------------------------------

The issue of security came up again, and Ka-Ping Yee suggested that in
Python's restricted execution mode secure proxies can be created by
using lexical scoping.  He posted `some code`_ for revealing only
certain "facets" of an object by using a function to declare a proxy
class that used a function's local variables to build the proxy. Thus
to access the attributes used in the proxy class, you need to access
things like im_func or func_closure, which are not accessible in
restricted execution mode.

James Y Knight illustrated how strategic overriding of __eq__ in a
subclass of str could allow access to the hidden "facets". Eyal Lotem
suggested that such an attack could be countered by implementing
"facets" in C, but having to turn to C every time you needed a
particular security construct seemed unappealing.

Contributing threads:

- `Security capabilities in Python
<http://mail.python.org/pipermail/python-dev/2005-April/052580.html>`__

..=2E _some code: http://zesty.ca/python/facet.py

[SJB]

---------------------------------
Improving GilState API Robustness
---------------------------------

Michael Hudson noted that his changes to thread handling in the
readline module appeared to trigger `bug 1176893`_ ("Readline
segfault"). However, he believed the problem lay in the GilState API,
rather than in his changes: PyGilState_Release crashes if
PyEval_InitThreads wasn't called, even if the code you're writing
doesn't use multiple threads.

He proposed several solutions, but no clear favorite emerged from
respondents, and Tim Peters noted that `PEP 311`_, Simplified Global
Interpreter Lock Acquisition for Extensions, "specifically disowns
responsibility for worrying about whether Py_Initialize and
PyEval_InitThreads have been called."  After further discussion,
Michael checked in a change to PyGilState_Release that calls
PyEval_SaveThread instead of PyEval_ReleaseThread, fixing the problem.

Bob Ippolito wondered whether just calling PyEval_InitThreads directly
in Py_Initialize might be a better idea.  No objections were raised,
so long as the underlying OS locking mechanisms weren't overly
expensive; some initial benchmarks indicated that this approach was
viable, at least on Linux and OS X.

Contributing threads:

- `threading (GilState) question
<http://mail.python.org/pipermail/python-dev/2005-April/052562.html>`__

..=2E _bug 1176893: http://www.python.org/sf/1176893

..=2E _PEP 311: http://www.python.org/peps/pep-0311.html

[TDL]

----------------------------------------
Unicode byte order mark decoding
----------------------------------------

Evan Jones saw that the UTF-16 decoder discards the byte-order mark
(BOM) from Unicode files, while the UTF-8 decoder doesn't. Although
the BOM isn't really required in UTF-8 files, many Unicode-generating
applications, especially on Microsoft platforms, add it.

Walter D=F6rwald created a patch_ to add a UTF-8-Sig codec that
generates a BOM on writing and skips it on reading. A long discussion
ensued on the history of the Unicode standard and Microsoft's
influence over its evolution.  Stephen Turnbull suggested (and
Marc-Andre Lemburg agreed) that BOM and signature handling be moved to
a higher-level API, but no overall consensus was achieved.

Contributing threads:

- `Unicode byte order mark decoding
<http://mail.python.org/pipermail/python-dev/2005-April/052501.html>`__

..=2E _patch: http://www.python.org/sf/1177307

[TDL]

--------------------
Marshalling Infinity
--------------------

Scott David Daniels kicked off a very long thread by asking what
(un)marshal should do with floating point NaNs.  The current behaviour
(as with any NaN, infinity, or signed zero) is undefined: a
platform-dependant accident, because Python is written to C89, which
has no such concepts.  Tim Peters pointed out all code for
(de)serialing C doubles should go through
_PyFloat_Pack8()/_PyFloat_Unpack8(), and that the current
implementation suggests that the routines could simply copy bytes on
platforms that use the standard IEEE-754 single and double formats
natively.  Michael Hudson obliged by creating a `patch to implement
this`_.

The consensus was that the correct behaviour is that packing a NaN or
infinity shouldn't cause an exception.  When unpacking, an IEEE-754
platform shouldn't cause an exception, but a non-754 platform should,
since there's no sensible value that it can be unpacked to, and errors
should never pass silently.

Contributing threads:

- `marshal / unmarshal
<http://mail.python.org/pipermail/python-dev/2005-April/052593.html>`__

..=2E _patch to implement this: http://python.org/sf/1181301

[TAM]

---------------------------------
Location of the sign bit in longs
---------------------------------

Michael Hudson asked about the possibility of longs storing the sign
bit somewhere other than the current location, suggesting the top bit
of ob_digit[0].  Tim Peters suggested that it would be better to give
struct _longobject a distinct sign member.  This simplifies code,
costs no extra bytes for some longs, and 8 extra bytes for others, and
shouldn't hurt binary compatibility.

Michael coughed up a `longobject patch`_, which seems likely to be
checked in.

Contributing threads:

- `marshal / unmarshal
<http://mail.python.org/pipermail/python-dev/2005-April/052593.html>`__

..=2E _longobject patch: http://python.org/sf/1177779

[TAM]


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Skipped Threads
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- python-dev Summary for 2005-03-16 through 2005-03-31 [draft]
- [Python-checkins] python/dist/src/Lib/logging handlers.py, 1.19,
1=2E19.2.1
- [Python-checkins] python/dist/src/Modules mathmodule.c, 2.74, 2.75
- Weekly Python Patch/Bug Summary
- Mail.python.org
- New bug, directly assigned, okay?
- inconsistency when swapping obj.__dict__ with a dict-like object...
- Pickling instances of nested classes
- args attribute of Exception objects



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Epilogue
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------------
Introduction
------------

This is a summary of traffic on the `python-dev mailing list`_ from
April 01, 2005 through April 15, 2005.  It is intended to inform the
wider Python community of on-going developments on the list on a
semi-monthly basis.  An archive_ of previous summaries is available
online.

An `RSS feed`_ of the titles of the summaries is available.  You can
also watch comp.lang.python or comp.lang.python.announce for new
summaries (or through their email gateways of python-list or
python-announce, respectively, as found at http://mail.python.org).

This is the first summary written by the python-dev summary cabal of
Steve Bethard, Tim Lesher, and Tony Meyer (So long, Brett, and thanks
for all the fish!).

To contact us, please send email:

- Steve Bethard (steven.bethard at gmail.com)
- Tim Lesher (tlesher at gmail.com)
- Tony Meyer (tony.meyer at gmail.com)

Do *not* post to comp.lang.python if you wish to reach us.

The `Python Software Foundation`_ is the non-profit organization that
holds the intellectual property for Python.  It also tries to advance
the development and use of Python.  If you find the python-dev Summary
helpful please consider making a donation.  You can make a donation at
http://python.org/psf/donations.html .  Every penny helps so even a
small donation with a credit card, check, or by PayPal helps.


--------------------
Commenting on Topics
--------------------

To comment on anything mentioned here, just post to
`comp.lang.python`_ (or email python-list@python.org 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 `python-dev`_!


-------------------------
How to Read the Summaries
-------------------------

The in-development version of the documentation for Python can be
found at http://www.python.org/dev/doc/devel/ and should be used when
looking up any documentation for new code; otherwise use the current
documentation as found at http://docs.python.org/ .  PEPs (Python
Enhancement Proposals) are located at http://www.python.org/peps/ .
To view files in the Python CVS online, go to
http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/python/ .  Reported
bugs and suggested patches can be found at the SourceForge_ project
page.

Please note that this summary is written using reStructuredText_.  Any
unfamiliar punctuation is probably markup for reST_ (otherwise it is
probably regular expression syntax or a typo =3D); you can safely ignore
it.  I do suggest learning reST, though; it's simple and is accepted
for `PEP markup`_ and can be turned into many different formats like
HTML and LaTeX.  Unfortunately, even though reST is standardized, the
wonders of programs that like to reformat text do not allow me to
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`_.

..=2E _python-dev: http://www.python.org/dev/
..=2E _SourceForge: http://sourceforge.net/tracker/?group_id=3D5470
..=2E _python-dev mailing list:
http://mail.python.org/mailman/listinfo/python-dev
..=2E _c.l.py:
..=2E _comp.lang.python:
http://groups.google.com/groups?q=3Dcomp.lang.python
..=2E _PEP Markup: http://www.python.org/peps/pep-0012.html

..=2E _Docutils: http://docutils.sf.net/
..=2E _reST:
..=2E _reStructuredText: http://docutils.sf.net/rst.html
..=2E _PSF:
..=2E _Python Software Foundation: http://python.org/psf/

..=2E _last summary: http://www.python.org/dev/summary/
..=2E _original text file:
http://www.python.org/dev/summary/2005-04-01_2005-04-15.ht
..=2E _archive: http://www.python.org/dev/summary/
..=2E _RSS feed: http://www.python.org/dev/summary/channews.rdf

0
tlesher (13)
4/21/2005 12:21:17 AM
comp.lang.python 77058 articles. 6 followers. Post Follow

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Tim Lesher wrote:

> ---------------------------
> New python-dev summary team
> ---------------------------
> 
> This summary marks the first by the team of Steve Bethard, Tim Lesher,
> and Tony Meyer.  We're trying a collaborative approach to the
> summaries: each fortnight, we'll be getting together in a virtual
> smoke-filled back room to divide up the interesting threads.  Then
> we'll stitch together the summaries in roughly the same form as you've
> seen in the past. We'll mark each editor's entries with his initials.
> 
+1

This first summary is a good start! Thanks.

> Thanks to Brett Cannon for sixty-one excellent python-dev summaries.
> Also, thanks for providing scripts to help get the new summaries off
> the ground! We're looking forward to the contributions you'll make to
> the Python core, now that the summaries aren't taking up all your
> time.

+1

Brett, thanks a lot!

regards, Gerrit
--
Praktijk voor Psychosociale therapie Lia Charit´┐Ż
http://www.liacharite.nl/
0
gmuller (21)
4/21/2005 6:44:25 PM
Reply: