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****************************
What's New In Python 3.1
****************************
.. XXX Add trademark info for Apple, Microsoft.
:Author: No one so far
:Release: |release|
:Date: |today|
.. $Id$
Rules for maintenance:
* Anyone can add text to this document. Do not spend very much time
on the wording of your changes, because your text will probably
get rewritten to some degree.
* The maintainer will go through Misc/NEWS periodically and add
changes; it's therefore more important to add your changes to
Misc/NEWS than to this file. (Note: I didn't get to this for 3.0.
GvR.)
* This is not a complete list of every single change; completeness
is the purpose of Misc/NEWS. Some changes I consider too small
or esoteric to include. If such a change is added to the text,
I'll just remove it. (This is another reason you shouldn't spend
too much time on writing your addition.)
* If you want to draw your new text to the attention of the
maintainer, add 'XXX' to the beginning of the paragraph or
section.
* It's OK to just add a fragmentary note about a change. For
example: "XXX Describe the transmogrify() function added to the
socket module." The maintainer will research the change and
write the necessary text.
* You can comment out your additions if you like, but it's not
necessary (especially when a final release is some months away).
* Credit the author of a patch or bugfix. Just the name is
sufficient; the e-mail address isn't necessary. (Due to time
constraints I haven't managed to do this for 3.0. GvR.)
* It's helpful to add the bug/patch number as a comment:
% Patch 12345
XXX Describe the transmogrify() function added to the socket
module.
(Contributed by P.Y. Developer.)
This saves the maintainer the effort of going through the SVN log
when researching a change. (Again, I didn't get to this for 3.0.
GvR.)
This article explains the new features in Python 3.1, compared to 3.0.
.. Compare with previous release in 2 - 3 sentences here.
.. add hyperlink when the documentation becomes available online.
.. ======================================================================
.. Large, PEP-level features and changes should be described here.
.. Should there be a new section here for 3k migration?
.. Or perhaps a more general section describing module changes/deprecation?
.. sets module deprecated
.. ======================================================================
Other Language Changes
======================
Some smaller changes made to the core Python language are:
* The :func:`int` type gained a ``bit_length`` method that returns the
number of bits necessary to represent its argument in binary::
>>> n = 37
>>> bin(37)
'0b100101'
>>> n.bit_length()
6
>>> n = 2**123-1
>>> n.bit_length()
123
>>> (n+1).bit_length()
124
(Contributed by Fredrik Johansson and Victor Stinner; :issue:`3439`.)
* Integers are now stored internally either in base 2**15 or in base
2**30, the base being determined at build time. Previously, they
were always stored in base 2**15. Using base 2**30 gives
significant performance improvements on 64-bit machines, but
benchmark results on 32-bit machines have been mixed. Therefore,
the default is to use base 2**30 on 64-bit machines and base 2**15
on 32-bit machines; on Unix, there's a new configure option
--enable-big-digits that can be used to override this default.
Apart from the performance improvements this change should be
invisible to end users, with one exception: for testing and
debugging purposes there's a new structseq ``sys.int_info`` that
provides information about the internal format, giving the number of
bits per digit and the size in bytes of the C type used to store
each digit::
>>> import sys
>>> sys.int_info
sys.int_info(bits_per_digit=30, sizeof_digit=4)
(Contributed by Mark Dickinson; :issue:`4258`.)
.. ======================================================================
Optimizations
-------------
Major performance enhancements have been added:
* The new I/O library (as defined in :pep:`3116`) was mostly written in
Python and quickly proved to be a problematic bottleneck in Python 3.0.
In Python 3.1, the I/O library has been entirely rewritten in C and is
2 to 20 times faster depending on the task at hand. The pure Python
version is still available for experimentation purposes through
the ``_pyio`` module.
(Contributed by Amaury Forgeot d'Arc and Antoine Pitrou.)
* A new configure flag, ``--with-computed-gotos``, enables a faster opcode
dispatch mechanism on compilers which support it. Speedups of up to 20%
have been observed, depending on the system and compiler.
(Contributed by Antoine Pitrou, :issue:`4753`.)
.. ======================================================================
|
