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.. _whats-new-in-2.6: **************************** What's New in Python 2.6 **************************** .. XXX add trademark info for Apple, Microsoft, SourceForge. :Author: A.M. Kuchling (amk at amk.ca) :Release: |release| :Date: |today| .. $Id: 2.6.rst 73214 2009-06-04 10:21:10Z georg.brandl $ 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. * 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. * It's helpful to add the bug/patch number in a parenthetical comment. XXX Describe the transmogrify() function added to the socket module. (Contributed by P.Y. Developer; :issue:`12345`.) This saves the maintainer some effort going through the SVN logs when researching a change. This article explains the new features in Python 2.6, released on October 1 2008. The release schedule is described in :pep:`361`. The major theme of Python 2.6 is preparing the migration path to Python 3.0, a major redesign of the language. Whenever possible, Python 2.6 incorporates new features and syntax from 3.0 while remaining compatible with existing code by not removing older features or syntax. When it's not possible to do that, Python 2.6 tries to do what it can, adding compatibility functions in a :mod:`future_builtins` module and a :option:`-3` switch to warn about usages that will become unsupported in 3.0. Some significant new packages have been added to the standard library, such as the :mod:`multiprocessing` and :mod:`json` modules, but there aren't many new features that aren't related to Python 3.0 in some way. Python 2.6 also sees a number of improvements and bugfixes throughout the source. A search through the change logs finds there were 259 patches applied and 612 bugs fixed between Python 2.5 and 2.6. Both figures are likely to be underestimates. This article doesn't attempt to provide a complete specification of the new features, but instead provides a convenient overview. For full details, you should refer to the documentation for Python 2.6. If you want to understand the rationale for the design and implementation, refer to the PEP for a particular new feature. Whenever possible, "What's New in Python" links to the bug/patch item for each change. .. 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. .. ======================================================================== Python 3.0 ================ The development cycle for Python versions 2.6 and 3.0 was synchronized, with the alpha and beta releases for both versions being made on the same days. The development of 3.0 has influenced many features in 2.6. Python 3.0 is a far-ranging redesign of Python that breaks compatibility with the 2.x series. This means that existing Python code will need some conversion in order to run on Python 3.0. However, not all the changes in 3.0 necessarily break compatibility. In cases where new features won't cause existing code to break, they've been backported to 2.6 and are described in this document in the appropriate place. Some of the 3.0-derived features are: * A :meth:`__complex__` method for converting objects to a complex number. * Alternate syntax for catching exceptions: ``except TypeError as exc``. * The addition of :func:`functools.reduce` as a synonym for the built-in :func:`reduce` function. Python 3.0 adds several new built-in functions and changes the semantics of some existing built-ins. Functions that are new in 3.0 such as :func:`bin` have simply been added to Python 2.6, but existing built-ins haven't been changed; instead, the :mod:`future_builtins` module has versions with the new 3.0 semantics. Code written to be compatible with 3.0 can do ``from future_builtins import hex, map`` as necessary. A new command-line switch, :option:`-3`, enables warnings about features that will be removed in Python 3.0. You can run code with this switch to see how much work will be necessary to port code to 3.0. The value of this switch is available to Python code as the boolean variable :data:`sys.py3kwarning`, and to C extension code as :cdata:`Py_Py3kWarningFlag`. .. seealso:: The 3xxx series of PEPs, which contains proposals for Python 3.0. :pep:`3000` describes the development process for Python 3.0. Start with :pep:`3100` that describes the general goals for Python 3.0, and then explore the higher-numbered PEPS that propose specific features. Changes to the Development Process ================================================== While 2.6 was being developed, the Python development process underwent two significant changes: we switched from SourceForge's issue tracker to a customized Roundup installation, and the documentation was converted from LaTeX to reStructuredText. New Issue Tracker: Roundup -------------------------------------------------- For a long time, the Python developers had been growing increasingly annoyed by SourceForge's bug tracker. SourceForge's hosted solution doesn't permit much customization; for example, it wasn't possible to customize the life cycle of issues. The infrastructure committee of the Python Software Foundation therefore posted a call for issue trackers, asking volunteers to set up different products and import some of the bugs and patches from SourceForge. Four different trackers were examined: `Jira <http://www.atlassian.com/software/jira/>`__, `Launchpad <http://www.launchpad.net>`__, `Roundup <http://roundup.sourceforge.net/>`__, and `Trac <http://trac.edgewall.org/>`__. The committee eventually settled on Jira and Roundup as the two candidates. Jira is a commercial product that offers no-cost hosted instances to free-software projects; Roundup is an open-source project that requires volunteers to administer it and a server to host it. After posting a call for volunteers, a new Roundup installation was set up at http://bugs.python.org. One installation of Roundup can host multiple trackers, and this server now also hosts issue trackers for Jython and for the Python web site. It will surely find other uses in the future. Where possible, this edition of "What's New in Python" links to the bug/patch item for each change. Hosting of the Python bug tracker is kindly provided by `Upfront Systems <http://www.upfrontsystems.co.za/>`__ of Stellenbosch, South Africa. Martin von Loewis put a lot of effort into importing existing bugs and patches from SourceForge; his scripts for this import operation are at http://svn.python.org/view/tracker/importer/ and may be useful to other projects wishing to move from SourceForge to Roundup. .. seealso:: http://bugs.pyth