python-dev Summary for 2003-10-16 through 2003-11-15

Brett C. bac at OCF.Berkeley.EDU
Thu Nov 27 20:33:39 CET 2003


python-dev Summary for 2003-10-16 through 2003-11-15
++++++++++++++++++++++++++++++++++++++++++++++++++++
This is a summary of traffic on the `python-dev mailing list`_ from 
October 16, 2003 through November 15, 2003.  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 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`_!

This is the twenty-eighth and twenty-ninth summaries written by Brett 
Cannon (does anyone even read this?).

All summaries are archived at http://www.python.org/dev/summary/ .

Please note that this summary is written using reStructuredText_ which 
can be found at http://docutils.sf.net/rst.html .  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: http://www.python.org/peps/pep-0012.html

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 on something mentioned here.  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.

.. _python-dev: http://www.python.org/dev/
.. _SourceForge: http://sourceforge.net/tracker/?group_id=5470
.. _python-dev mailing list: 
http://mail.python.org/mailman/listinfo/python-dev
.. _comp.lang.python: http://groups.google.com/groups?q=comp.lang.python
.. _Docutils: http://docutils.sf.net/
.. _reST:
.. _reStructuredText: http://docutils.sf.net/rst.html

.. contents::

.. _last summary: 
http://www.python.org/dev/summary/2003-09-01_2003-09-15.html



=====================
Summary Announcements
=====================
Thanks to midterms and projects my time got eaten up by school.  That 
postponed when I could work on the twenty-eighth summary so much that 
the twenty-ninth was need of being written.  So they are combined in 
into one to just get the stuff out the door.

The second half of October had some major discussions happen.  Guido and 
Alex Martelli talking equals pain for me.  =)

There was a large discussion on scoping and accessing specific 
namespaces.  Jeremy Hylton is working on a PEP on the subject so I am 
not going to stress myself over summarizing the topic.

A big discussion on the first half of November was about weakrefs and 
shutdown.  Tim Peters figured out the problem (had to do with weakrefs 
referencing things already gc'ed and thus throwing a fit when trying to 
gc them later or keeping an object alive because of the weakref).  It 
was long and complicated, but the problem was solved.

If you have ever wanted to see linked lists used in Python in a rather 
elegant way, take a look at Guido's implementation of itertools.tee at 
http://mail.python.org/pipermail/python-dev/2003-October/039593.html .

Europython is going to be held from June 7-9, 2004 in Sweden.  See 
http://mail.python.org/pipermail/europython/2003-November/003634.html 
for more details.

PyCon is slowly moving along.  The registration site is being put 
through QA and the paper submission system is being worked on.  The Call 
for Proposals (CFP) is still on-going; details at 
http://www.python.org/pycon/dc2004/cfp.html .  Keep an eye out for when 
we announce when the registration and paper submission systems go live.


=========
Summaries
=========
------------------------------------------
How to help with the development of Python
------------------------------------------
In an attempt to make it easy as possible for people to find out how 
they can help contribute to Python's development, I wrote an essay on 
the topic (mentioned last month, but some revisions have been done).  It 
covers how Python is developed and how **anyone** can contribute to the 
development process.  The latest version can be found at 
http://mail.python.org/pipermail/python-dev/2003-October/039473.html .

Any comments on the essay are appreciated.

Contributing threads:
   - `Draft of an essay on Python development 
<http://mail.python.org/pipermail/python-dev/2003-October/038677.html>`__
   - `2nd draft of "How Py is Developed" essay 
<http://mail.python.org/pipermail/python-dev/2003-October/039473.html>`__


------------------------------------------------
Generator Expressions: list comp's older brother
------------------------------------------------
If you ever wanted to have the power of list comprehensions but without 
the overhead of generating the entire list you have Peter Norvig to 
thank initially, and then what seems like the rest of the world, for 
generator expressions.

`PEP 289`_ covers all the details, but here is a quick intro.  You can 
think of generator expressions as list comprehensions that return an 
iterator for each item instead a list items.  The syntax is practically 
the same as list comprehensions as well; just substitute parentheses for 
square brackets (most of the time; generator expressions just need 
parentheses around them, so being the only argument to a method takes 
care of the parentheses requirement).

A quick example is::

   (x for x in range(10) if x%2)

returns an iterator that returns the odd numbers from 0 to 10.  This 
make list comprehensions just syntactic sugar for passing a generator 
expression to list() (note how extra parentheses are not needed)::

   list(x for x in range(10) is x%2)

Having list comprehensions defined this way also takes away the dangling 
item variable for the 'for' loop.  Using that dangling variable is now 
discouraged and will be made illegal at some point.

For complete details, read the PEP.

.. _PEP 289: http://www.python.org/peps/pep-0289.html

Contributing threads:
   - `decorate-sort-undecorate 
<http://mail.python.org/pipermail/python-dev/2003-October/038652.html>`__
   - `accumulator display syntax 
<http://mail.python.org/pipermail/python-dev/2003-October/038804.html>`__
   - `listcomps vs. for loops 
<http://mail.python.org/pipermail/python-dev/2003-October/039081.html>`__
   - `PEP 289: Generator Expressions (second draft) 
<http://mail.python.org/pipermail/python-dev/2003-October/039356.html>`__


---------------------
list.sorted() is born
---------------------
After the addition of the 'key' argument to list.sort(), people began to 
clamor for list.sort() to return self.  Guido refused to do give in, so 
a compromise was reached.  'list' now has a class method named 'sorted'; 
pass it an iterable and it will return a sorted list.

Contributing threads:
   - `decorate-sort-undecorate 
<http://mail.python.org/pipermail/python-dev/2003-October/038811.html>`__
   - `inline sort option 
<http://mail.python.org/pipermail/python-dev/2003-October/038825.html>`__
   - `sort() return value 
<http://mail.python.org/pipermail/python-dev/2003-October/038855.html>`__
   - `copysort patch 
<http://mail.python.org/pipermail/python-dev/2003-October/038947.html>`__


------------------------------------
Recursion limit in re is now history
------------------------------------
Thanks to Gustavo Niemeyer the recursion limit in the re module has now 
be removed!

Contributing threads:
   - `SRE recursion 
<http://mail.python.org/pipermail/python-dev/2003-October/038839.html>`__
   - `SRE recursion removed 
<http://mail.python.org/pipermail/python-dev/2003-October/038962.html>`__


-----------------------------------
Copying iterators one day at a time
-----------------------------------
Reiteration for iterators came up as part of the immense discussion on 
generator expressions.  The difficulty of doing it generally came up. 
This lead to Alex Martelli proposing magic method support for __copy__ 
in iterators that have want to allow making a copy of itself.  This was 
written down as `PEP 323`_.

As an interim solution, itertools grew a new function: tee.  It takes in 
an iterable and returns two or more iterators which independently 
iterate over the iterable.

.. _PEP 323: http://www.python.org/peps/pep-0323.html

Contributing threads:
   - `Reiterability 
<http://mail.python.org/pipermail/python-dev/2003-October/038969.html>`__
   - `cloning iterators again 
<http://mail.python.org/pipermail/python-dev/2003-October/039593.html>`__
   - `... python/nondist/peps pep-0323.txt, NONE ... 
<http://mail.python.org/pipermail/python-dev/2003-October/039656.html>`__
   - `Guido's Magic Code 
<http://mail.python.org/pipermail/python-dev/2003-October/039819.html>`__


------------------------------------------------------
Returning Py_(None, True, False) now easier than ever!
------------------------------------------------------
Py_RETURN_NONE, Py_RETURN_TRUE, and Py_RETURN_FALSE have been added to 
Python 2.4.  They are macros for returning the singleton mentioned in 
the name.  Documentation has yet to be written (my fault).

Contributing threads:
   - `How to spell Py_return_None and friends 
<http://mail.python.org/pipermail/python-dev/2003-October/039000.html>`__
   - `python/dist/src/Include object.h, 2.121, ... 
<http://mail.python.org/pipermail/python-dev/2003-October/039026.html>`__


-------------------------------------------------------------------------
'String substitutions'/'dict interpolation'/'replace %(blah)s with $blah'
-------------------------------------------------------------------------
The idea of introducing string substitutions using '$' came up.  Guido 
said that if this was made a built-in feature it would have to wait 
until Python 3.  He was receptive to moving the functionality to a 
module, though.

Barry Warsaw pasted code into 
http://mail.python.org/pipermail/python-dev/2003-October/039369.html 
that handles string substitutions.

Contributing threads:
   - `Can we please have a better dict interpolation syntax? 
<http://mail.python.org/pipermail/python-dev/2003-October/039324.html>`__


------------------------------------------
"reduce() just doesn't get enough mileage"
------------------------------------------
That quote comes from Guido during the discussion over whether 'product' 
should be added as an accumulator function built-in like 'sum'.  The 
idea was shot down and conversation quickly turned to whether 'reduce' 
should stay in the language (the consensus was "no" since the function 
does not read well and its functionality can easily be done with a 'for' 
loop).

A larger discussion on what built-ins should eventually disappear will 
be covered in the next Summary.

Contributing threads:
   - `product() 
<http://mail.python.org/pipermail/python-dev/2003-October/039326.html>`__


-----------
PyPy update
-----------
The PyPy_ development group sent an update on their happenings to the 
list.  Turns out they are trying to get funding from the European Union. 
  They are also fairly close to getting a working version (albeit with 
some bootstrapping from CPython, but it will still be damn cool what 
they have pulled off even with this caveat).

They also announced a sprint they are holding in Amsterdam from Dec. 
14-21.  More info can be found at 
http://codespeak.net/moin/pypy/moin.cgi/AmsterdamSprint .

.. _PyPy: http://codespeak.net/pypy/

Contributing threads:
   - `PyPy: sprint and news 
<http://mail.python.org/pipermail/python-dev/2003-October/039579.html>`__


----------------------------
Never say Python is finished
----------------------------
I asked python-dev for masters thesis ideas.  I great number of 
possibilities were put out.  If anyone out there is curious to see what 
some people would like to see done for Python in terms of a large 
project check the thread out.

Contributing threads:
   - `Looking for master thesis ideas involving Python 
<http://mail.python.org/pipermail/python-dev/2003-October/039763.html>`__


---------------------------------
Rough draft of Decimal object PEP
---------------------------------
Facundo Batista has posted a rough draft of a PEP for a decimal object 
that is being worked on in the sandbox.  Comment on it on 
`comp.lang.python`_ if this interests you.

Contributing threads:
   - `prePEP: Decimal data type 
<http://mail.python.org/pipermail/python-dev/2003-October/039870.html>`__


----------------------------------------------------------
Relations of basestring and bye-bye operator.isMappingType
----------------------------------------------------------
The idea of introducing relatives of basestring for numbers came from 
Alex Martelli.  That idea was shot down for not being needed once the 
merger of int and long occurs.

The point that operator.isMappingType is kind of broken came up.  Both 
Alex and Raymond Hettinger would not mind seeing it disappear.  No one 
objected.  It is still in CVS at the moment, but I would not count on it 
necessarily sticking around (although there are rumblings that there 
might be a way to fix it so it is partially useful).


Contributed threads:
   - `reflections on basestring -- and other abstract basetypes 
<http://mail.python.org/pipermail/python-dev/2003-November/039885.html>`__
   - `operator.isMappingType 
<http://mail.python.org/pipermail/python-dev/2003-November/040122.html>`__


---------------------------------------------------------
Why one checks into the trunk before a maintenance branch
---------------------------------------------------------
The question of whether checking a change into a maintenance branch 
before applying it to the main trunk was acceptable came up.  The short 
answer is "no".  Basically the trunk gets more testing than the 
maintenance branches and thus the patch should have to prove its 
stability first.  Only then should it go into a maintenance branch.

The same goes for changes to code that will eventually disappear in the 
trunk.  Someone might be planning on removing some code, but if that 
person falls off the face of the earth the code will still be there. 
That means applying the patch to the code that is scheduled to disappear 
is still a good idea.

Contributing threads:
   - `check-in policy, trunk vs maintenance branch 
<http://mail.python.org/pipermail/python-dev/2003-November/039903.html>`__


-----------------------
New reversed() built-in
-----------------------
There was a new built-in named reversed(), and all rejoiced after giving 
the creator a thorough beating.

Straight from the function's doc string: "reverse iterator over values 
of the sequence".  `PEP 322`_ has the relevant details on this new built-in.

.. _PEP 322: http://www.python.org/peps/pep-0322.html

Contributing threads:
   - `PEP 322:  Reverse Iteration 
<http://mail.python.org/pipermail/python-dev/2003-November/039924.html>`__


---------------------------
Cleaning the built-in house
---------------------------
Guido asked what built-ins should be considered for deprecation. 
Instantly intern, coerce, and apply came up.  apply already had a 
PendingDeprecationWarning and that will stay for the next release or 
two.  intern and coerce, though, did not have any major champions 
(intern had some fans, but just for the functionality).

Guido did state that none of these built-in will be removed any time 
soon.  If they do get deprecated it does not lead to immediate removal. 
  Python 3, though, takes the gloves off and that can see them just 
completely disappear.

Contributing threads:
   - `Deprecating obsolete builtins 
<http://mail.python.org/pipermail/python-dev/2003-November/039994.html>`__


----------------------------------------
Passing arguments to str.(encode|decode)
----------------------------------------
The idea of allowing keyword arguments be passed to any specified 
encoder/decoder was brought up by Raymond Hettinger.  It seemed like an 
idea that was supported.  The idea of specifying the encoder or decoder 
based on the actual object instead of the current way of specifying a 
string that is passed to the registered codec search functions was 
suggested.

Nothing has been finalized on this idea as of now.

Contributing threads:
   - `Optional arguments for str.encode /.decode 
<http://mail.python.org/pipermail/python-dev/2003-November/040055.html>`__



------------------------------------------------------
Where, oh where, to move the good stuff out of string?
------------------------------------------------------
It looks like ascii_* and possibly maketrans from the string module will 
be tacked on to the str type so that the string module can finally be 
removed from the language.  It has not been pronounced upon, but it 
looks like that is what the BDFL is leaning towards.

Issues of using the methods of str as unbound methods did come up.  As 
it stands you cannot pass a unicode object to str.upper and thus there 
is no one uppercasing function as there is in the string module.  This 
issue brought up the problem of Unicode and locale ties and collation 
(how to sort things).

Contributing threads:
   - `other "magic strings" issues 
<http://mail.python.org/pipermail/python-dev/2003-November/040067.html>`__


-----------------------------------------
Supported versions of Sleepycat for bsddb
-----------------------------------------
The basic answer is 3.2 - 4.2 should work when you compile from source.

Contributing threads:
   - `which sleepycat versions do we support in 2.3.* ? 
<http://mail.python.org/pipermail/python-dev/2003-November/040196.html>`__


-----------------------------
Sets now at blazing C speeds!
-----------------------------
Raymond Hettinger implemented the sets API in C!  The new built-ins are 
set (which replaces sets.Set) and frozenset (which replaces 
sets.ImmutableSet).  The APIs are the same as the sets module sans the 
name change from ImmutableSet to frozenset.

Contributing threads:
   - `set() and frozenset() 
<http://mail.python.org/pipermail/python-dev/2003-November/040253.html>`__






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