mirror of https://github.com/python/cpython
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120 KiB
ReStructuredText
2801 lines
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ReStructuredText
****************************
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What's New in Python 2.7
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****************************
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:Author: A.M. Kuchling (amk at amk.ca)
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.. hyperlink all the methods & functions.
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.. T_STRING_INPLACE not described in main docs
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.. $Id$
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Rules for maintenance:
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* Anyone can add text to this document. Do not spend very much time
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on the wording of your changes, because your text will probably
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get rewritten to some degree.
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* The maintainer will go through Misc/NEWS periodically and add
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changes; it's therefore more important to add your changes to
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Misc/NEWS than to this file.
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* This is not a complete list of every single change; completeness
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is the purpose of Misc/NEWS. Some changes I consider too small
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or esoteric to include. If such a change is added to the text,
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I'll just remove it. (This is another reason you shouldn't spend
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too much time on writing your addition.)
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* If you want to draw your new text to the attention of the
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maintainer, add 'XXX' to the beginning of the paragraph or
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section.
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* It's OK to just add a fragmentary note about a change. For
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example: "XXX Describe the transmogrify() function added to the
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socket module." The maintainer will research the change and
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write the necessary text.
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* You can comment out your additions if you like, but it's not
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necessary (especially when a final release is some months away).
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* Credit the author of a patch or bugfix. Just the name is
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sufficient; the e-mail address isn't necessary.
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* It's helpful to add the bug/patch number in a parenthetical comment.
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XXX Describe the transmogrify() function added to the socket
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module.
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(Contributed by P.Y. Developer; :issue:`12345`.)
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This saves the maintainer some effort going through the SVN logs
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when researching a change.
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This article explains the new features in Python 2.7. Python 2.7 was released
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on July 3, 2010.
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Numeric handling has been improved in many ways, for both
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floating-point numbers and for the :class:`~decimal.Decimal` class.
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There are some useful additions to the standard library, such as a
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greatly enhanced :mod:`unittest` module, the :mod:`argparse` module
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for parsing command-line options, convenient :class:`~collections.OrderedDict`
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and :class:`~collections.Counter` classes in the :mod:`collections` module,
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and many other improvements.
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Python 2.7 is planned to be the last of the 2.x releases, so we worked
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on making it a good release for the long term. To help with porting
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to Python 3, several new features from the Python 3.x series have been
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included in 2.7.
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This article doesn't attempt to provide a complete specification of
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the new features, but instead provides a convenient overview. For
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full details, you should refer to the documentation for Python 2.7 at
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https://docs.python.org. If you want to understand the rationale for
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the design and implementation, refer to the PEP for a particular new
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feature or the issue on https://bugs.python.org in which a change was
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discussed. Whenever possible, "What's New in Python" links to the
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bug/patch item for each change.
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.. _whatsnew27-python31:
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The Future for Python 2.x
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=========================
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Python 2.7 is the last major release in the 2.x series, as the Python
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maintainers have shifted the focus of their new feature development efforts
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to the Python 3.x series. This means that while Python 2 continues to
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receive bug fixes, and to be updated to build correctly on new hardware and
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versions of supported operated systems, there will be no new full feature
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releases for the language or standard library.
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However, while there is a large common subset between Python 2.7 and Python
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3, and many of the changes involved in migrating to that common subset, or
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directly to Python 3, can be safely automated, some other changes (notably
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those associated with Unicode handling) may require careful consideration,
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and preferably robust automated regression test suites, to migrate
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effectively.
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This means that Python 2.7 will remain in place for a long time, providing a
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stable and supported base platform for production systems that have not yet
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been ported to Python 3. The full expected lifecycle of the Python 2.7
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series is detailed in :pep:`373`.
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Some key consequences of the long-term significance of 2.7 are:
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* As noted above, the 2.7 release has a much longer period of maintenance
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when compared to earlier 2.x versions. Python 2.7 is currently expected to
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remain supported by the core development team (receiving security updates
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and other bug fixes) until at least 2020 (10 years after its initial
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release, compared to the more typical support period of 18--24 months).
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* As the Python 2.7 standard library ages, making effective use of the
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Python Package Index (either directly or via a redistributor) becomes
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more important for Python 2 users. In addition to a wide variety of third
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party packages for various tasks, the available packages include backports
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of new modules and features from the Python 3 standard library that are
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compatible with Python 2, as well as various tools and libraries that can
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make it easier to migrate to Python 3. The `Python Packaging User Guide
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<https://packaging.python.org>`__ provides guidance on downloading and
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installing software from the Python Package Index.
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* While the preferred approach to enhancing Python 2 is now the publication
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of new packages on the Python Package Index, this approach doesn't
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necessarily work in all cases, especially those related to network
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security. In exceptional cases that cannot be handled adequately by
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publishing new or updated packages on PyPI, the Python Enhancement
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Proposal process may be used to make the case for adding new features
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directly to the Python 2 standard library. Any such additions, and the
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maintenance releases where they were added, will be noted in the
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:ref:`py27-maintenance-enhancements` section below.
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For projects wishing to migrate from Python 2 to Python 3, or for library
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and framework developers wishing to support users on both Python 2 and
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Python 3, there are a variety of tools and guides available to help decide
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on a suitable approach and manage some of the technical details involved.
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The recommended starting point is the :ref:`pyporting-howto` HOWTO guide.
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Changes to the Handling of Deprecation Warnings
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===============================================
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For Python 2.7, a policy decision was made to silence warnings only of
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interest to developers by default. :exc:`DeprecationWarning` and its
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descendants are now ignored unless otherwise requested, preventing
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users from seeing warnings triggered by an application. This change
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was also made in the branch that became Python 3.2. (Discussed
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on stdlib-sig and carried out in :issue:`7319`.)
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In previous releases, :exc:`DeprecationWarning` messages were
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enabled by default, providing Python developers with a clear
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indication of where their code may break in a future major version
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of Python.
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However, there are increasingly many users of Python-based
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applications who are not directly involved in the development of
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those applications. :exc:`DeprecationWarning` messages are
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irrelevant to such users, making them worry about an application
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that's actually working correctly and burdening application developers
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with responding to these concerns.
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You can re-enable display of :exc:`DeprecationWarning` messages by
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running Python with the :option:`-Wdefault <-W>` (short form:
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:option:`-Wd <-W>`) switch, or by setting the :envvar:`PYTHONWARNINGS`
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environment variable to ``"default"`` (or ``"d"``) before running
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Python. Python code can also re-enable them
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by calling ``warnings.simplefilter('default')``.
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The ``unittest`` module also automatically reenables deprecation warnings
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when running tests.
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Python 3.1 Features
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=======================
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Much as Python 2.6 incorporated features from Python 3.0,
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version 2.7 incorporates some of the new features
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in Python 3.1. The 2.x series continues to provide tools
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for migrating to the 3.x series.
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A partial list of 3.1 features that were backported to 2.7:
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* The syntax for set literals (``{1,2,3}`` is a mutable set).
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* Dictionary and set comprehensions (``{i: i*2 for i in range(3)}``).
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* Multiple context managers in a single :keyword:`with` statement.
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* A new version of the :mod:`io` library, rewritten in C for performance.
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* The ordered-dictionary type described in :ref:`pep-0372`.
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* The new ``","`` format specifier described in :ref:`pep-0378`.
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* The :class:`memoryview` object.
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* A small subset of the :mod:`importlib` module,
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`described below <#importlib-section>`__.
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* The :func:`repr` of a float ``x`` is shorter in many cases: it's now
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based on the shortest decimal string that's guaranteed to round back
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to ``x``. As in previous versions of Python, it's guaranteed that
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``float(repr(x))`` recovers ``x``.
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* Float-to-string and string-to-float conversions are correctly rounded.
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The :func:`round` function is also now correctly rounded.
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* The :c:type:`PyCapsule` type, used to provide a C API for extension modules.
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* The :c:func:`PyLong_AsLongAndOverflow` C API function.
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Other new Python3-mode warnings include:
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* :func:`operator.isCallable` and :func:`operator.sequenceIncludes`,
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which are not supported in 3.x, now trigger warnings.
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* The :option:`!-3` switch now automatically
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enables the :option:`!-Qwarn` switch that causes warnings
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about using classic division with integers and long integers.
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.. ========================================================================
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.. Large, PEP-level features and changes should be described here.
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.. ========================================================================
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.. _pep-0372:
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PEP 372: Adding an Ordered Dictionary to collections
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====================================================
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Regular Python dictionaries iterate over key/value pairs in arbitrary order.
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Over the years, a number of authors have written alternative implementations
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that remember the order that the keys were originally inserted. Based on
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the experiences from those implementations, 2.7 introduces a new
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:class:`~collections.OrderedDict` class in the :mod:`collections` module.
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The :class:`~collections.OrderedDict` API provides the same interface as regular
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dictionaries but iterates over keys and values in a guaranteed order
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depending on when a key was first inserted::
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>>> from collections import OrderedDict
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>>> d = OrderedDict([('first', 1),
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... ('second', 2),
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... ('third', 3)])
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>>> d.items()
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[('first', 1), ('second', 2), ('third', 3)]
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If a new entry overwrites an existing entry, the original insertion
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position is left unchanged::
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>>> d['second'] = 4
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>>> d.items()
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[('first', 1), ('second', 4), ('third', 3)]
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Deleting an entry and reinserting it will move it to the end::
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>>> del d['second']
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>>> d['second'] = 5
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>>> d.items()
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[('first', 1), ('third', 3), ('second', 5)]
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The :meth:`~collections.OrderedDict.popitem` method has an optional *last*
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argument that defaults to ``True``. If *last* is true, the most recently
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added key is returned and removed; if it's false, the
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oldest key is selected::
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>>> od = OrderedDict([(x,0) for x in range(20)])
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>>> od.popitem()
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(19, 0)
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>>> od.popitem()
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(18, 0)
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>>> od.popitem(last=False)
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(0, 0)
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>>> od.popitem(last=False)
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(1, 0)
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Comparing two ordered dictionaries checks both the keys and values,
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and requires that the insertion order was the same::
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>>> od1 = OrderedDict([('first', 1),
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... ('second', 2),
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... ('third', 3)])
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>>> od2 = OrderedDict([('third', 3),
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... ('first', 1),
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... ('second', 2)])
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>>> od1 == od2
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False
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>>> # Move 'third' key to the end
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>>> del od2['third']; od2['third'] = 3
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>>> od1 == od2
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True
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Comparing an :class:`~collections.OrderedDict` with a regular dictionary
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ignores the insertion order and just compares the keys and values.
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How does the :class:`~collections.OrderedDict` work? It maintains a
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doubly linked list of keys, appending new keys to the list as they're inserted.
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A secondary dictionary maps keys to their corresponding list node, so
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deletion doesn't have to traverse the entire linked list and therefore
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remains O(1).
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The standard library now supports use of ordered dictionaries in several
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modules.
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* The :mod:`ConfigParser` module uses them by default, meaning that
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configuration files can now be read, modified, and then written back
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in their original order.
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* The :meth:`~collections.somenamedtuple._asdict()` method for
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:func:`collections.namedtuple` now returns an ordered dictionary with the
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values appearing in the same order as the underlying tuple indices.
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* The :mod:`json` module's :class:`~json.JSONDecoder` class
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constructor was extended with an *object_pairs_hook* parameter to
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allow :class:`OrderedDict` instances to be built by the decoder.
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Support was also added for third-party tools like
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`PyYAML <https://pyyaml.org/>`_.
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.. seealso::
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:pep:`372` - Adding an ordered dictionary to collections
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PEP written by Armin Ronacher and Raymond Hettinger;
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implemented by Raymond Hettinger.
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.. _pep-0378:
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PEP 378: Format Specifier for Thousands Separator
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=================================================
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To make program output more readable, it can be useful to add
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separators to large numbers, rendering them as
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18,446,744,073,709,551,616 instead of 18446744073709551616.
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The fully general solution for doing this is the :mod:`locale` module,
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which can use different separators ("," in North America, "." in
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Europe) and different grouping sizes, but :mod:`locale` is complicated
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to use and unsuitable for multi-threaded applications where different
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threads are producing output for different locales.
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Therefore, a simple comma-grouping mechanism has been added to the
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mini-language used by the :meth:`str.format` method. When
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formatting a floating-point number, simply include a comma between the
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width and the precision::
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>>> '{:20,.2f}'.format(18446744073709551616.0)
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'18,446,744,073,709,551,616.00'
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When formatting an integer, include the comma after the width:
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>>> '{:20,d}'.format(18446744073709551616)
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'18,446,744,073,709,551,616'
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This mechanism is not adaptable at all; commas are always used as the
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separator and the grouping is always into three-digit groups. The
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comma-formatting mechanism isn't as general as the :mod:`locale`
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module, but it's easier to use.
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.. seealso::
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:pep:`378` - Format Specifier for Thousands Separator
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PEP written by Raymond Hettinger; implemented by Eric Smith.
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PEP 389: The argparse Module for Parsing Command Lines
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======================================================
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The :mod:`argparse` module for parsing command-line arguments was
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added as a more powerful replacement for the
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:mod:`optparse` module.
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This means Python now supports three different modules for parsing
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command-line arguments: :mod:`getopt`, :mod:`optparse`, and
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:mod:`argparse`. The :mod:`getopt` module closely resembles the C
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library's :c:func:`getopt` function, so it remains useful if you're writing a
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Python prototype that will eventually be rewritten in C.
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:mod:`optparse` becomes redundant, but there are no plans to remove it
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because there are many scripts still using it, and there's no
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automated way to update these scripts. (Making the :mod:`argparse`
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API consistent with :mod:`optparse`'s interface was discussed but
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rejected as too messy and difficult.)
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In short, if you're writing a new script and don't need to worry
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about compatibility with earlier versions of Python, use
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:mod:`argparse` instead of :mod:`optparse`.
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Here's an example::
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import argparse
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parser = argparse.ArgumentParser(description='Command-line example.')
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# Add optional switches
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parser.add_argument('-v', action='store_true', dest='is_verbose',
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help='produce verbose output')
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parser.add_argument('-o', action='store', dest='output',
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metavar='FILE',
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help='direct output to FILE instead of stdout')
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parser.add_argument('-C', action='store', type=int, dest='context',
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metavar='NUM', default=0,
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help='display NUM lines of added context')
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# Allow any number of additional arguments.
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parser.add_argument(nargs='*', action='store', dest='inputs',
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help='input filenames (default is stdin)')
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args = parser.parse_args()
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print args.__dict__
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Unless you override it, :option:`!-h` and :option:`!--help` switches
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are automatically added, and produce neatly formatted output::
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-> ./python.exe argparse-example.py --help
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usage: argparse-example.py [-h] [-v] [-o FILE] [-C NUM] [inputs [inputs ...]]
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Command-line example.
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positional arguments:
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inputs input filenames (default is stdin)
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optional arguments:
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-h, --help show this help message and exit
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-v produce verbose output
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-o FILE direct output to FILE instead of stdout
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-C NUM display NUM lines of added context
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As with :mod:`optparse`, the command-line switches and arguments
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are returned as an object with attributes named by the *dest* parameters::
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-> ./python.exe argparse-example.py -v
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{'output': None,
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'is_verbose': True,
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'context': 0,
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'inputs': []}
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-> ./python.exe argparse-example.py -v -o /tmp/output -C 4 file1 file2
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{'output': '/tmp/output',
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'is_verbose': True,
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'context': 4,
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'inputs': ['file1', 'file2']}
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:mod:`argparse` has much fancier validation than :mod:`optparse`; you
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can specify an exact number of arguments as an integer, 0 or more
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arguments by passing ``'*'``, 1 or more by passing ``'+'``, or an
|
|
optional argument with ``'?'``. A top-level parser can contain
|
|
sub-parsers to define subcommands that have different sets of
|
|
switches, as in ``svn commit``, ``svn checkout``, etc. You can
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|
specify an argument's type as :class:`~argparse.FileType`, which will
|
|
automatically open files for you and understands that ``'-'`` means
|
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standard input or output.
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.. seealso::
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:mod:`argparse` documentation
|
|
The documentation page of the argparse module.
|
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:ref:`upgrading-optparse-code`
|
|
Part of the Python documentation, describing how to convert
|
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code that uses :mod:`optparse`.
|
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:pep:`389` - argparse - New Command Line Parsing Module
|
|
PEP written and implemented by Steven Bethard.
|
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PEP 391: Dictionary-Based Configuration For Logging
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====================================================
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The :mod:`logging` module is very flexible; applications can define
|
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a tree of logging subsystems, and each logger in this tree can filter
|
|
out certain messages, format them differently, and direct messages to
|
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a varying number of handlers.
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All this flexibility can require a lot of configuration. You can
|
|
write Python statements to create objects and set their properties,
|
|
but a complex set-up requires verbose but boring code.
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|
:mod:`logging` also supports a :func:`~logging.fileConfig`
|
|
function that parses a file, but the file format doesn't support
|
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configuring filters, and it's messier to generate programmatically.
|
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|
|
Python 2.7 adds a :func:`~logging.dictConfig` function that
|
|
uses a dictionary to configure logging. There are many ways to
|
|
produce a dictionary from different sources: construct one with code;
|
|
parse a file containing JSON; or use a YAML parsing library if one is
|
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installed. For more information see :ref:`logging-config-api`.
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|
The following example configures two loggers, the root logger and a
|
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logger named "network". Messages sent to the root logger will be
|
|
sent to the system log using the syslog protocol, and messages
|
|
to the "network" logger will be written to a :file:`network.log` file
|
|
that will be rotated once the log reaches 1MB.
|
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::
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import logging
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import logging.config
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configdict = {
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'version': 1, # Configuration schema in use; must be 1 for now
|
|
'formatters': {
|
|
'standard': {
|
|
'format': ('%(asctime)s %(name)-15s '
|
|
'%(levelname)-8s %(message)s')}},
|
|
|
|
'handlers': {'netlog': {'backupCount': 10,
|
|
'class': 'logging.handlers.RotatingFileHandler',
|
|
'filename': '/logs/network.log',
|
|
'formatter': 'standard',
|
|
'level': 'INFO',
|
|
'maxBytes': 1000000},
|
|
'syslog': {'class': 'logging.handlers.SysLogHandler',
|
|
'formatter': 'standard',
|
|
'level': 'ERROR'}},
|
|
|
|
# Specify all the subordinate loggers
|
|
'loggers': {
|
|
'network': {
|
|
'handlers': ['netlog']
|
|
}
|
|
},
|
|
# Specify properties of the root logger
|
|
'root': {
|
|
'handlers': ['syslog']
|
|
},
|
|
}
|
|
|
|
# Set up configuration
|
|
logging.config.dictConfig(configdict)
|
|
|
|
# As an example, log two error messages
|
|
logger = logging.getLogger('/')
|
|
logger.error('Database not found')
|
|
|
|
netlogger = logging.getLogger('network')
|
|
netlogger.error('Connection failed')
|
|
|
|
Three smaller enhancements to the :mod:`logging` module, all
|
|
implemented by Vinay Sajip, are:
|
|
|
|
.. rev79293
|
|
|
|
* The :class:`~logging.handlers.SysLogHandler` class now supports
|
|
syslogging over TCP. The constructor has a *socktype* parameter
|
|
giving the type of socket to use, either :const:`socket.SOCK_DGRAM`
|
|
for UDP or :const:`socket.SOCK_STREAM` for TCP. The default
|
|
protocol remains UDP.
|
|
|
|
* :class:`~logging.Logger` instances gained a :meth:`~logging.Logger.getChild`
|
|
method that retrieves a descendant logger using a relative path.
|
|
For example, once you retrieve a logger by doing ``log = getLogger('app')``,
|
|
calling ``log.getChild('network.listen')`` is equivalent to
|
|
``getLogger('app.network.listen')``.
|
|
|
|
* The :class:`~logging.LoggerAdapter` class gained an
|
|
:meth:`~logging.LoggerAdapter.isEnabledFor` method that takes a
|
|
*level* and returns whether the underlying logger would
|
|
process a message of that level of importance.
|
|
|
|
.. XXX: Logger objects don't have a class declaration so the link don't work
|
|
|
|
.. seealso::
|
|
|
|
:pep:`391` - Dictionary-Based Configuration For Logging
|
|
PEP written and implemented by Vinay Sajip.
|
|
|
|
PEP 3106: Dictionary Views
|
|
====================================================
|
|
|
|
The dictionary methods :meth:`~dict.keys`, :meth:`~dict.values`, and
|
|
:meth:`~dict.items` are different in Python 3.x. They return an object
|
|
called a :dfn:`view` instead of a fully materialized list.
|
|
|
|
It's not possible to change the return values of :meth:`~dict.keys`,
|
|
:meth:`~dict.values`, and :meth:`~dict.items` in Python 2.7 because
|
|
too much code would break. Instead the 3.x versions were added
|
|
under the new names :meth:`~dict.viewkeys`, :meth:`~dict.viewvalues`,
|
|
and :meth:`~dict.viewitems`.
|
|
|
|
::
|
|
|
|
>>> d = dict((i*10, chr(65+i)) for i in range(26))
|
|
>>> d
|
|
{0: 'A', 130: 'N', 10: 'B', 140: 'O', 20: ..., 250: 'Z'}
|
|
>>> d.viewkeys()
|
|
dict_keys([0, 130, 10, 140, 20, 150, 30, ..., 250])
|
|
|
|
Views can be iterated over, but the key and item views also behave
|
|
like sets. The ``&`` operator performs intersection, and ``|``
|
|
performs a union::
|
|
|
|
>>> d1 = dict((i*10, chr(65+i)) for i in range(26))
|
|
>>> d2 = dict((i**.5, i) for i in range(1000))
|
|
>>> d1.viewkeys() & d2.viewkeys()
|
|
set([0.0, 10.0, 20.0, 30.0])
|
|
>>> d1.viewkeys() | range(0, 30)
|
|
set([0, 1, 130, 3, 4, 5, 6, ..., 120, 250])
|
|
|
|
The view keeps track of the dictionary and its contents change as the
|
|
dictionary is modified::
|
|
|
|
>>> vk = d.viewkeys()
|
|
>>> vk
|
|
dict_keys([0, 130, 10, ..., 250])
|
|
>>> d[260] = '&'
|
|
>>> vk
|
|
dict_keys([0, 130, 260, 10, ..., 250])
|
|
|
|
However, note that you can't add or remove keys while you're iterating
|
|
over the view::
|
|
|
|
>>> for k in vk:
|
|
... d[k*2] = k
|
|
...
|
|
Traceback (most recent call last):
|
|
File "<stdin>", line 1, in <module>
|
|
RuntimeError: dictionary changed size during iteration
|
|
|
|
You can use the view methods in Python 2.x code, and the 2to3
|
|
converter will change them to the standard :meth:`~dict.keys`,
|
|
:meth:`~dict.values`, and :meth:`~dict.items` methods.
|
|
|
|
.. seealso::
|
|
|
|
:pep:`3106` - Revamping dict.keys(), .values() and .items()
|
|
PEP written by Guido van Rossum.
|
|
Backported to 2.7 by Alexandre Vassalotti; :issue:`1967`.
|
|
|
|
|
|
PEP 3137: The memoryview Object
|
|
====================================================
|
|
|
|
The :class:`memoryview` object provides a view of another object's
|
|
memory content that matches the :class:`bytes` type's interface.
|
|
|
|
.. doctest::
|
|
:options: +SKIP
|
|
|
|
>>> import string
|
|
>>> m = memoryview(string.letters)
|
|
>>> m
|
|
<memory at 0x37f850>
|
|
>>> len(m) # Returns length of underlying object
|
|
52
|
|
>>> m[0], m[25], m[26] # Indexing returns one byte
|
|
('a', 'z', 'A')
|
|
>>> m2 = m[0:26] # Slicing returns another memoryview
|
|
>>> m2
|
|
<memory at 0x37f080>
|
|
|
|
The content of the view can be converted to a string of bytes or
|
|
a list of integers:
|
|
|
|
.. doctest::
|
|
:options: +SKIP
|
|
|
|
>>> m2.tobytes()
|
|
'abcdefghijklmnopqrstuvwxyz'
|
|
>>> m2.tolist()
|
|
[97, 98, 99, 100, 101, 102, 103, ... 121, 122]
|
|
>>>
|
|
|
|
:class:`memoryview` objects allow modifying the underlying object if
|
|
it's a mutable object.
|
|
|
|
.. doctest::
|
|
:options: +SKIP
|
|
|
|
>>> m2[0] = 75
|
|
Traceback (most recent call last):
|
|
File "<stdin>", line 1, in <module>
|
|
TypeError: cannot modify read-only memory
|
|
>>> b = bytearray(string.letters) # Creating a mutable object
|
|
>>> b
|
|
bytearray(b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ')
|
|
>>> mb = memoryview(b)
|
|
>>> mb[0] = '*' # Assign to view, changing the bytearray.
|
|
>>> b[0:5] # The bytearray has been changed.
|
|
bytearray(b'*bcde')
|
|
>>>
|
|
|
|
.. seealso::
|
|
|
|
:pep:`3137` - Immutable Bytes and Mutable Buffer
|
|
PEP written by Guido van Rossum.
|
|
Implemented by Travis Oliphant, Antoine Pitrou and others.
|
|
Backported to 2.7 by Antoine Pitrou; :issue:`2396`.
|
|
|
|
|
|
|
|
Other Language Changes
|
|
======================
|
|
|
|
Some smaller changes made to the core Python language are:
|
|
|
|
* The syntax for set literals has been backported from Python 3.x.
|
|
Curly brackets are used to surround the contents of the resulting
|
|
mutable set; set literals are
|
|
distinguished from dictionaries by not containing colons and values.
|
|
``{}`` continues to represent an empty dictionary; use
|
|
``set()`` for an empty set.
|
|
|
|
.. doctest::
|
|
:options: +SKIP
|
|
|
|
>>> {1, 2, 3, 4, 5}
|
|
set([1, 2, 3, 4, 5])
|
|
>>> set() # empty set
|
|
set([])
|
|
>>> {} # empty dict
|
|
{}
|
|
|
|
Backported by Alexandre Vassalotti; :issue:`2335`.
|
|
|
|
* Dictionary and set comprehensions are another feature backported from
|
|
3.x, generalizing list/generator comprehensions to use
|
|
the literal syntax for sets and dictionaries.
|
|
|
|
.. doctest::
|
|
:options: +SKIP
|
|
|
|
>>> {x: x*x for x in range(6)}
|
|
{0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25}
|
|
>>> {('a'*x) for x in range(6)}
|
|
set(['', 'a', 'aa', 'aaa', 'aaaa', 'aaaaa'])
|
|
|
|
Backported by Alexandre Vassalotti; :issue:`2333`.
|
|
|
|
* The :keyword:`with` statement can now use multiple context managers
|
|
in one statement. Context managers are processed from left to right
|
|
and each one is treated as beginning a new :keyword:`!with` statement.
|
|
This means that::
|
|
|
|
with A() as a, B() as b:
|
|
... suite of statements ...
|
|
|
|
is equivalent to::
|
|
|
|
with A() as a:
|
|
with B() as b:
|
|
... suite of statements ...
|
|
|
|
The :func:`contextlib.nested` function provides a very similar
|
|
function, so it's no longer necessary and has been deprecated.
|
|
|
|
(Proposed in https://codereview.appspot.com/53094; implemented by
|
|
Georg Brandl.)
|
|
|
|
* Conversions between floating-point numbers and strings are
|
|
now correctly rounded on most platforms. These conversions occur
|
|
in many different places: :func:`str` on
|
|
floats and complex numbers; the :class:`float` and :class:`complex`
|
|
constructors;
|
|
numeric formatting; serializing and
|
|
deserializing floats and complex numbers using the
|
|
:mod:`marshal`, :mod:`pickle`
|
|
and :mod:`json` modules;
|
|
parsing of float and imaginary literals in Python code;
|
|
and :class:`~decimal.Decimal`-to-float conversion.
|
|
|
|
Related to this, the :func:`repr` of a floating-point number *x*
|
|
now returns a result based on the shortest decimal string that's
|
|
guaranteed to round back to *x* under correct rounding (with
|
|
round-half-to-even rounding mode). Previously it gave a string
|
|
based on rounding x to 17 decimal digits.
|
|
|
|
.. maybe add an example?
|
|
|
|
The rounding library responsible for this improvement works on
|
|
Windows and on Unix platforms using the gcc, icc, or suncc
|
|
compilers. There may be a small number of platforms where correct
|
|
operation of this code cannot be guaranteed, so the code is not
|
|
used on such systems. You can find out which code is being used
|
|
by checking :data:`sys.float_repr_style`, which will be ``short``
|
|
if the new code is in use and ``legacy`` if it isn't.
|
|
|
|
Implemented by Eric Smith and Mark Dickinson, using David Gay's
|
|
:file:`dtoa.c` library; :issue:`7117`.
|
|
|
|
* Conversions from long integers and regular integers to floating
|
|
point now round differently, returning the floating-point number
|
|
closest to the number. This doesn't matter for small integers that
|
|
can be converted exactly, but for large numbers that will
|
|
unavoidably lose precision, Python 2.7 now approximates more
|
|
closely. For example, Python 2.6 computed the following::
|
|
|
|
>>> n = 295147905179352891391
|
|
>>> float(n)
|
|
2.9514790517935283e+20
|
|
>>> n - long(float(n))
|
|
65535L
|
|
|
|
Python 2.7's floating-point result is larger, but much closer to the
|
|
true value::
|
|
|
|
>>> n = 295147905179352891391
|
|
>>> float(n)
|
|
2.9514790517935289e+20
|
|
>>> n - long(float(n))
|
|
-1L
|
|
|
|
(Implemented by Mark Dickinson; :issue:`3166`.)
|
|
|
|
Integer division is also more accurate in its rounding behaviours. (Also
|
|
implemented by Mark Dickinson; :issue:`1811`.)
|
|
|
|
* Implicit coercion for complex numbers has been removed; the interpreter
|
|
will no longer ever attempt to call a :meth:`__coerce__` method on complex
|
|
objects. (Removed by Meador Inge and Mark Dickinson; :issue:`5211`.)
|
|
|
|
* The :meth:`str.format` method now supports automatic numbering of the replacement
|
|
fields. This makes using :meth:`str.format` more closely resemble using
|
|
``%s`` formatting::
|
|
|
|
>>> '{}:{}:{}'.format(2009, 04, 'Sunday')
|
|
'2009:4:Sunday'
|
|
>>> '{}:{}:{day}'.format(2009, 4, day='Sunday')
|
|
'2009:4:Sunday'
|
|
|
|
The auto-numbering takes the fields from left to right, so the first ``{...}``
|
|
specifier will use the first argument to :meth:`str.format`, the next
|
|
specifier will use the next argument, and so on. You can't mix auto-numbering
|
|
and explicit numbering -- either number all of your specifier fields or none
|
|
of them -- but you can mix auto-numbering and named fields, as in the second
|
|
example above. (Contributed by Eric Smith; :issue:`5237`.)
|
|
|
|
Complex numbers now correctly support usage with :func:`format`,
|
|
and default to being right-aligned.
|
|
Specifying a precision or comma-separation applies to both the real
|
|
and imaginary parts of the number, but a specified field width and
|
|
alignment is applied to the whole of the resulting ``1.5+3j``
|
|
output. (Contributed by Eric Smith; :issue:`1588` and :issue:`7988`.)
|
|
|
|
The 'F' format code now always formats its output using uppercase characters,
|
|
so it will now produce 'INF' and 'NAN'.
|
|
(Contributed by Eric Smith; :issue:`3382`.)
|
|
|
|
A low-level change: the :meth:`object.__format__` method now triggers
|
|
a :exc:`PendingDeprecationWarning` if it's passed a format string,
|
|
because the :meth:`__format__` method for :class:`object` converts
|
|
the object to a string representation and formats that. Previously
|
|
the method silently applied the format string to the string
|
|
representation, but that could hide mistakes in Python code. If
|
|
you're supplying formatting information such as an alignment or
|
|
precision, presumably you're expecting the formatting to be applied
|
|
in some object-specific way. (Fixed by Eric Smith; :issue:`7994`.)
|
|
|
|
* The :func:`int` and :func:`long` types gained a ``bit_length``
|
|
method that returns the number of bits necessary to represent
|
|
its argument in binary::
|
|
|
|
>>> n = 37
|
|
>>> bin(n)
|
|
'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`.)
|
|
|
|
* The :keyword:`import` statement will no longer try an absolute import
|
|
if a relative import (e.g. ``from .os import sep``) fails. This
|
|
fixes a bug, but could possibly break certain :keyword:`!import`
|
|
statements that were only working by accident. (Fixed by Meador Inge;
|
|
:issue:`7902`.)
|
|
|
|
* It's now possible for a subclass of the built-in :class:`unicode` type
|
|
to override the :meth:`__unicode__` method. (Implemented by
|
|
Victor Stinner; :issue:`1583863`.)
|
|
|
|
* The :class:`bytearray` type's :meth:`~bytearray.translate` method now accepts
|
|
``None`` as its first argument. (Fixed by Georg Brandl;
|
|
:issue:`4759`.)
|
|
|
|
.. XXX bytearray doesn't seem to be documented
|
|
|
|
* When using ``@classmethod`` and ``@staticmethod`` to wrap
|
|
methods as class or static methods, the wrapper object now
|
|
exposes the wrapped function as their :attr:`__func__` attribute.
|
|
(Contributed by Amaury Forgeot d'Arc, after a suggestion by
|
|
George Sakkis; :issue:`5982`.)
|
|
|
|
* When a restricted set of attributes were set using ``__slots__``,
|
|
deleting an unset attribute would not raise :exc:`AttributeError`
|
|
as you would expect. Fixed by Benjamin Peterson; :issue:`7604`.)
|
|
|
|
* Two new encodings are now supported: "cp720", used primarily for
|
|
Arabic text; and "cp858", a variant of CP 850 that adds the euro
|
|
symbol. (CP720 contributed by Alexander Belchenko and Amaury
|
|
Forgeot d'Arc in :issue:`1616979`; CP858 contributed by Tim Hatch in
|
|
:issue:`8016`.)
|
|
|
|
* The :class:`file` object will now set the :attr:`filename` attribute
|
|
on the :exc:`IOError` exception when trying to open a directory
|
|
on POSIX platforms (noted by Jan Kaliszewski; :issue:`4764`), and
|
|
now explicitly checks for and forbids writing to read-only file objects
|
|
instead of trusting the C library to catch and report the error
|
|
(fixed by Stefan Krah; :issue:`5677`).
|
|
|
|
* The Python tokenizer now translates line endings itself, so the
|
|
:func:`compile` built-in function now accepts code using any
|
|
line-ending convention. Additionally, it no longer requires that the
|
|
code end in a newline.
|
|
|
|
* Extra parentheses in function definitions are illegal in Python 3.x,
|
|
meaning that you get a syntax error from ``def f((x)): pass``. In
|
|
Python3-warning mode, Python 2.7 will now warn about this odd usage.
|
|
(Noted by James Lingard; :issue:`7362`.)
|
|
|
|
* It's now possible to create weak references to old-style class
|
|
objects. New-style classes were always weak-referenceable. (Fixed
|
|
by Antoine Pitrou; :issue:`8268`.)
|
|
|
|
* When a module object is garbage-collected, the module's dictionary is
|
|
now only cleared if no one else is holding a reference to the
|
|
dictionary (:issue:`7140`).
|
|
|
|
.. ======================================================================
|
|
|
|
.. _new-27-interpreter:
|
|
|
|
Interpreter Changes
|
|
-------------------------------
|
|
|
|
A new environment variable, :envvar:`PYTHONWARNINGS`,
|
|
allows controlling warnings. It should be set to a string
|
|
containing warning settings, equivalent to those
|
|
used with the :option:`-W` switch, separated by commas.
|
|
(Contributed by Brian Curtin; :issue:`7301`.)
|
|
|
|
For example, the following setting will print warnings every time
|
|
they occur, but turn warnings from the :mod:`Cookie` module into an
|
|
error. (The exact syntax for setting an environment variable varies
|
|
across operating systems and shells.)
|
|
|
|
::
|
|
|
|
export PYTHONWARNINGS=all,error:::Cookie:0
|
|
|
|
.. ======================================================================
|
|
|
|
|
|
Optimizations
|
|
-------------
|
|
|
|
Several performance enhancements have been added:
|
|
|
|
* A new opcode was added to perform the initial setup for
|
|
:keyword:`with` statements, looking up the :meth:`__enter__` and
|
|
:meth:`__exit__` methods. (Contributed by Benjamin Peterson.)
|
|
|
|
* The garbage collector now performs better for one common usage
|
|
pattern: when many objects are being allocated without deallocating
|
|
any of them. This would previously take quadratic
|
|
time for garbage collection, but now the number of full garbage collections
|
|
is reduced as the number of objects on the heap grows.
|
|
The new logic only performs a full garbage collection pass when
|
|
the middle generation has been collected 10 times and when the
|
|
number of survivor objects from the middle generation exceeds 10% of
|
|
the number of objects in the oldest generation. (Suggested by Martin
|
|
von Löwis and implemented by Antoine Pitrou; :issue:`4074`.)
|
|
|
|
* The garbage collector tries to avoid tracking simple containers
|
|
which can't be part of a cycle. In Python 2.7, this is now true for
|
|
tuples and dicts containing atomic types (such as ints, strings,
|
|
etc.). Transitively, a dict containing tuples of atomic types won't
|
|
be tracked either. This helps reduce the cost of each
|
|
garbage collection by decreasing the number of objects to be
|
|
considered and traversed by the collector.
|
|
(Contributed by Antoine Pitrou; :issue:`4688`.)
|
|
|
|
* Long 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
|
|
: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 :data:`sys.long_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.long_info
|
|
sys.long_info(bits_per_digit=30, sizeof_digit=4)
|
|
|
|
(Contributed by Mark Dickinson; :issue:`4258`.)
|
|
|
|
Another set of changes made long objects a few bytes smaller: 2 bytes
|
|
smaller on 32-bit systems and 6 bytes on 64-bit.
|
|
(Contributed by Mark Dickinson; :issue:`5260`.)
|
|
|
|
* The division algorithm for long integers has been made faster
|
|
by tightening the inner loop, doing shifts instead of multiplications,
|
|
and fixing an unnecessary extra iteration.
|
|
Various benchmarks show speedups of between 50% and 150% for long
|
|
integer divisions and modulo operations.
|
|
(Contributed by Mark Dickinson; :issue:`5512`.)
|
|
Bitwise operations are also significantly faster (initial patch by
|
|
Gregory Smith; :issue:`1087418`).
|
|
|
|
* The implementation of ``%`` checks for the left-side operand being
|
|
a Python string and special-cases it; this results in a 1--3%
|
|
performance increase for applications that frequently use ``%``
|
|
with strings, such as templating libraries.
|
|
(Implemented by Collin Winter; :issue:`5176`.)
|
|
|
|
* List comprehensions with an ``if`` condition are compiled into
|
|
faster bytecode. (Patch by Antoine Pitrou, back-ported to 2.7
|
|
by Jeffrey Yasskin; :issue:`4715`.)
|
|
|
|
* Converting an integer or long integer to a decimal string was made
|
|
faster by special-casing base 10 instead of using a generalized
|
|
conversion function that supports arbitrary bases.
|
|
(Patch by Gawain Bolton; :issue:`6713`.)
|
|
|
|
* The :meth:`split`, :meth:`replace`, :meth:`rindex`,
|
|
:meth:`rpartition`, and :meth:`rsplit` methods of string-like types
|
|
(strings, Unicode strings, and :class:`bytearray` objects) now use a
|
|
fast reverse-search algorithm instead of a character-by-character
|
|
scan. This is sometimes faster by a factor of 10. (Added by
|
|
Florent Xicluna; :issue:`7462` and :issue:`7622`.)
|
|
|
|
* The :mod:`pickle` and :mod:`cPickle` modules now automatically
|
|
intern the strings used for attribute names, reducing memory usage
|
|
of the objects resulting from unpickling. (Contributed by Jake
|
|
McGuire; :issue:`5084`.)
|
|
|
|
* The :mod:`cPickle` module now special-cases dictionaries,
|
|
nearly halving the time required to pickle them.
|
|
(Contributed by Collin Winter; :issue:`5670`.)
|
|
|
|
.. ======================================================================
|
|
|
|
New and Improved Modules
|
|
========================
|
|
|
|
As in every release, Python's standard library received a number of
|
|
enhancements and bug fixes. Here's a partial list of the most notable
|
|
changes, sorted alphabetically by module name. Consult the
|
|
:file:`Misc/NEWS` file in the source tree for a more complete list of
|
|
changes, or look through the Subversion logs for all the details.
|
|
|
|
* The :mod:`bdb` module's base debugging class :class:`~bdb.Bdb`
|
|
gained a feature for skipping modules. The constructor
|
|
now takes an iterable containing glob-style patterns such as
|
|
``django.*``; the debugger will not step into stack frames
|
|
from a module that matches one of these patterns.
|
|
(Contributed by Maru Newby after a suggestion by
|
|
Senthil Kumaran; :issue:`5142`.)
|
|
|
|
* The :mod:`binascii` module now supports the buffer API, so it can be
|
|
used with :class:`memoryview` instances and other similar buffer objects.
|
|
(Backported from 3.x by Florent Xicluna; :issue:`7703`.)
|
|
|
|
* Updated module: the :mod:`bsddb` module has been updated from 4.7.2devel9
|
|
to version 4.8.4 of
|
|
`the pybsddb package <https://www.jcea.es/programacion/pybsddb.htm>`__.
|
|
The new version features better Python 3.x compatibility, various bug fixes,
|
|
and adds several new BerkeleyDB flags and methods.
|
|
(Updated by Jesús Cea Avión; :issue:`8156`. The pybsddb
|
|
changelog can be read at https://hg.jcea.es/pybsddb/file/tip/ChangeLog.)
|
|
|
|
* The :mod:`bz2` module's :class:`~bz2.BZ2File` now supports the context
|
|
management protocol, so you can write ``with bz2.BZ2File(...) as f:``.
|
|
(Contributed by Hagen Fürstenau; :issue:`3860`.)
|
|
|
|
* New class: the :class:`~collections.Counter` class in the :mod:`collections`
|
|
module is useful for tallying data. :class:`~collections.Counter` instances
|
|
behave mostly like dictionaries but return zero for missing keys instead of
|
|
raising a :exc:`KeyError`:
|
|
|
|
.. doctest::
|
|
:options: +NORMALIZE_WHITESPACE
|
|
|
|
>>> from collections import Counter
|
|
>>> c = Counter()
|
|
>>> for letter in 'here is a sample of english text':
|
|
... c[letter] += 1
|
|
...
|
|
>>> c # doctest: +SKIP
|
|
Counter({' ': 6, 'e': 5, 's': 3, 'a': 2, 'i': 2, 'h': 2,
|
|
'l': 2, 't': 2, 'g': 1, 'f': 1, 'm': 1, 'o': 1, 'n': 1,
|
|
'p': 1, 'r': 1, 'x': 1})
|
|
>>> c['e']
|
|
5
|
|
>>> c['z']
|
|
0
|
|
|
|
There are three additional :class:`~collections.Counter` methods.
|
|
:meth:`~collections.Counter.most_common` returns the N most common
|
|
elements and their counts. :meth:`~collections.Counter.elements`
|
|
returns an iterator over the contained elements, repeating each
|
|
element as many times as its count.
|
|
:meth:`~collections.Counter.subtract` takes an iterable and
|
|
subtracts one for each element instead of adding; if the argument is
|
|
a dictionary or another :class:`Counter`, the counts are
|
|
subtracted. ::
|
|
|
|
>>> c.most_common(5)
|
|
[(' ', 6), ('e', 5), ('s', 3), ('a', 2), ('i', 2)]
|
|
>>> c.elements() ->
|
|
'a', 'a', ' ', ' ', ' ', ' ', ' ', ' ',
|
|
'e', 'e', 'e', 'e', 'e', 'g', 'f', 'i', 'i',
|
|
'h', 'h', 'm', 'l', 'l', 'o', 'n', 'p', 's',
|
|
's', 's', 'r', 't', 't', 'x'
|
|
>>> c['e']
|
|
5
|
|
>>> c.subtract('very heavy on the letter e')
|
|
>>> c['e'] # Count is now lower
|
|
-1
|
|
|
|
Contributed by Raymond Hettinger; :issue:`1696199`.
|
|
|
|
.. revision 79660
|
|
|
|
New class: :class:`~collections.OrderedDict` is described in the earlier
|
|
section :ref:`pep-0372`.
|
|
|
|
New method: The :class:`~collections.deque` data type now has a
|
|
:meth:`~collections.deque.count` method that returns the number of
|
|
contained elements equal to the supplied argument *x*, and a
|
|
:meth:`~collections.deque.reverse` method that reverses the elements
|
|
of the deque in-place. :class:`~collections.deque` also exposes its maximum
|
|
length as the read-only :attr:`~collections.deque.maxlen` attribute.
|
|
(Both features added by Raymond Hettinger.)
|
|
|
|
The :class:`~collections.namedtuple` class now has an optional *rename* parameter.
|
|
If *rename* is true, field names that are invalid because they've
|
|
been repeated or aren't legal Python identifiers will be
|
|
renamed to legal names that are derived from the field's
|
|
position within the list of fields:
|
|
|
|
>>> from collections import namedtuple
|
|
>>> T = namedtuple('T', ['field1', '$illegal', 'for', 'field2'], rename=True)
|
|
>>> T._fields
|
|
('field1', '_1', '_2', 'field2')
|
|
|
|
(Added by Raymond Hettinger; :issue:`1818`.)
|
|
|
|
Finally, the :class:`~collections.Mapping` abstract base class now
|
|
returns :const:`NotImplemented` if a mapping is compared to
|
|
another type that isn't a :class:`Mapping`.
|
|
(Fixed by Daniel Stutzbach; :issue:`8729`.)
|
|
|
|
* Constructors for the parsing classes in the :mod:`ConfigParser` module now
|
|
take an *allow_no_value* parameter, defaulting to false; if true,
|
|
options without values will be allowed. For example::
|
|
|
|
>>> import ConfigParser, StringIO
|
|
>>> sample_config = """
|
|
... [mysqld]
|
|
... user = mysql
|
|
... pid-file = /var/run/mysqld/mysqld.pid
|
|
... skip-bdb
|
|
... """
|
|
>>> config = ConfigParser.RawConfigParser(allow_no_value=True)
|
|
>>> config.readfp(StringIO.StringIO(sample_config))
|
|
>>> config.get('mysqld', 'user')
|
|
'mysql'
|
|
>>> print config.get('mysqld', 'skip-bdb')
|
|
None
|
|
>>> print config.get('mysqld', 'unknown')
|
|
Traceback (most recent call last):
|
|
...
|
|
NoOptionError: No option 'unknown' in section: 'mysqld'
|
|
|
|
(Contributed by Mats Kindahl; :issue:`7005`.)
|
|
|
|
* Deprecated function: :func:`contextlib.nested`, which allows
|
|
handling more than one context manager with a single :keyword:`with`
|
|
statement, has been deprecated, because the :keyword:`!with` statement
|
|
now supports multiple context managers.
|
|
|
|
* The :mod:`cookielib` module now ignores cookies that have an invalid
|
|
version field, one that doesn't contain an integer value. (Fixed by
|
|
John J. Lee; :issue:`3924`.)
|
|
|
|
* The :mod:`copy` module's :func:`~copy.deepcopy` function will now
|
|
correctly copy bound instance methods. (Implemented by
|
|
Robert Collins; :issue:`1515`.)
|
|
|
|
* The :mod:`ctypes` module now always converts ``None`` to a C ``NULL``
|
|
pointer for arguments declared as pointers. (Changed by Thomas
|
|
Heller; :issue:`4606`.) The underlying `libffi library
|
|
<https://sourceware.org/libffi/>`__ has been updated to version
|
|
3.0.9, containing various fixes for different platforms. (Updated
|
|
by Matthias Klose; :issue:`8142`.)
|
|
|
|
* New method: the :mod:`datetime` module's :class:`~datetime.timedelta` class
|
|
gained a :meth:`~datetime.timedelta.total_seconds` method that returns the
|
|
number of seconds in the duration. (Contributed by Brian Quinlan; :issue:`5788`.)
|
|
|
|
* New method: the :class:`~decimal.Decimal` class gained a
|
|
:meth:`~decimal.Decimal.from_float` class method that performs an exact
|
|
conversion of a floating-point number to a :class:`~decimal.Decimal`.
|
|
This exact conversion strives for the
|
|
closest decimal approximation to the floating-point representation's value;
|
|
the resulting decimal value will therefore still include the inaccuracy,
|
|
if any.
|
|
For example, ``Decimal.from_float(0.1)`` returns
|
|
``Decimal('0.1000000000000000055511151231257827021181583404541015625')``.
|
|
(Implemented by Raymond Hettinger; :issue:`4796`.)
|
|
|
|
Comparing instances of :class:`~decimal.Decimal` with floating-point
|
|
numbers now produces sensible results based on the numeric values
|
|
of the operands. Previously such comparisons would fall back to
|
|
Python's default rules for comparing objects, which produced arbitrary
|
|
results based on their type. Note that you still cannot combine
|
|
:class:`Decimal` and floating-point in other operations such as addition,
|
|
since you should be explicitly choosing how to convert between float and
|
|
:class:`~decimal.Decimal`. (Fixed by Mark Dickinson; :issue:`2531`.)
|
|
|
|
The constructor for :class:`~decimal.Decimal` now accepts
|
|
floating-point numbers (added by Raymond Hettinger; :issue:`8257`)
|
|
and non-European Unicode characters such as Arabic-Indic digits
|
|
(contributed by Mark Dickinson; :issue:`6595`).
|
|
|
|
Most of the methods of the :class:`~decimal.Context` class now accept integers
|
|
as well as :class:`~decimal.Decimal` instances; the only exceptions are the
|
|
:meth:`~decimal.Context.canonical` and :meth:`~decimal.Context.is_canonical`
|
|
methods. (Patch by Juan José Conti; :issue:`7633`.)
|
|
|
|
When using :class:`~decimal.Decimal` instances with a string's
|
|
:meth:`~str.format` method, the default alignment was previously
|
|
left-alignment. This has been changed to right-alignment, which is
|
|
more sensible for numeric types. (Changed by Mark Dickinson; :issue:`6857`.)
|
|
|
|
Comparisons involving a signaling NaN value (or ``sNAN``) now signal
|
|
:const:`InvalidOperation` instead of silently returning a true or
|
|
false value depending on the comparison operator. Quiet NaN values
|
|
(or ``NaN``) are now hashable. (Fixed by Mark Dickinson;
|
|
:issue:`7279`.)
|
|
|
|
* The :mod:`difflib` module now produces output that is more
|
|
compatible with modern :command:`diff`/:command:`patch` tools
|
|
through one small change, using a tab character instead of spaces as
|
|
a separator in the header giving the filename. (Fixed by Anatoly
|
|
Techtonik; :issue:`7585`.)
|
|
|
|
* The Distutils ``sdist`` command now always regenerates the
|
|
:file:`MANIFEST` file, since even if the :file:`MANIFEST.in` or
|
|
:file:`setup.py` files haven't been modified, the user might have
|
|
created some new files that should be included.
|
|
(Fixed by Tarek Ziadé; :issue:`8688`.)
|
|
|
|
* The :mod:`doctest` module's :const:`IGNORE_EXCEPTION_DETAIL` flag
|
|
will now ignore the name of the module containing the exception
|
|
being tested. (Patch by Lennart Regebro; :issue:`7490`.)
|
|
|
|
* The :mod:`email` module's :class:`~email.message.Message` class will
|
|
now accept a Unicode-valued payload, automatically converting the
|
|
payload to the encoding specified by :attr:`output_charset`.
|
|
(Added by R. David Murray; :issue:`1368247`.)
|
|
|
|
* The :class:`~fractions.Fraction` class now accepts a single float or
|
|
:class:`~decimal.Decimal` instance, or two rational numbers, as
|
|
arguments to its constructor. (Implemented by Mark Dickinson;
|
|
rationals added in :issue:`5812`, and float/decimal in
|
|
:issue:`8294`.)
|
|
|
|
Ordering comparisons (``<``, ``<=``, ``>``, ``>=``) between
|
|
fractions and complex numbers now raise a :exc:`TypeError`.
|
|
This fixes an oversight, making the :class:`~fractions.Fraction`
|
|
match the other numeric types.
|
|
|
|
.. revision 79455
|
|
|
|
* New class: :class:`~ftplib.FTP_TLS` in
|
|
the :mod:`ftplib` module provides secure FTP
|
|
connections using TLS encapsulation of authentication as well as
|
|
subsequent control and data transfers.
|
|
(Contributed by Giampaolo Rodola; :issue:`2054`.)
|
|
|
|
The :meth:`~ftplib.FTP.storbinary` method for binary uploads can now restart
|
|
uploads thanks to an added *rest* parameter (patch by Pablo Mouzo;
|
|
:issue:`6845`.)
|
|
|
|
* New class decorator: :func:`~functools.total_ordering` in the :mod:`functools`
|
|
module takes a class that defines an :meth:`__eq__` method and one of
|
|
:meth:`__lt__`, :meth:`__le__`, :meth:`__gt__`, or :meth:`__ge__`,
|
|
and generates the missing comparison methods. Since the
|
|
:meth:`__cmp__` method is being deprecated in Python 3.x,
|
|
this decorator makes it easier to define ordered classes.
|
|
(Added by Raymond Hettinger; :issue:`5479`.)
|
|
|
|
New function: :func:`~functools.cmp_to_key` will take an old-style comparison
|
|
function that expects two arguments and return a new callable that
|
|
can be used as the *key* parameter to functions such as
|
|
:func:`sorted`, :func:`min` and :func:`max`, etc. The primary
|
|
intended use is to help with making code compatible with Python 3.x.
|
|
(Added by Raymond Hettinger.)
|
|
|
|
* New function: the :mod:`gc` module's :func:`~gc.is_tracked` returns
|
|
true if a given instance is tracked by the garbage collector, false
|
|
otherwise. (Contributed by Antoine Pitrou; :issue:`4688`.)
|
|
|
|
* The :mod:`gzip` module's :class:`~gzip.GzipFile` now supports the context
|
|
management protocol, so you can write ``with gzip.GzipFile(...) as f:``
|
|
(contributed by Hagen Fürstenau; :issue:`3860`), and it now implements
|
|
the :class:`io.BufferedIOBase` ABC, so you can wrap it with
|
|
:class:`io.BufferedReader` for faster processing
|
|
(contributed by Nir Aides; :issue:`7471`).
|
|
It's also now possible to override the modification time
|
|
recorded in a gzipped file by providing an optional timestamp to
|
|
the constructor. (Contributed by Jacques Frechet; :issue:`4272`.)
|
|
|
|
Files in gzip format can be padded with trailing zero bytes; the
|
|
:mod:`gzip` module will now consume these trailing bytes. (Fixed by
|
|
Tadek Pietraszek and Brian Curtin; :issue:`2846`.)
|
|
|
|
* New attribute: the :mod:`hashlib` module now has an :attr:`~hashlib.hashlib.algorithms`
|
|
attribute containing a tuple naming the supported algorithms.
|
|
In Python 2.7, ``hashlib.algorithms`` contains
|
|
``('md5', 'sha1', 'sha224', 'sha256', 'sha384', 'sha512')``.
|
|
(Contributed by Carl Chenet; :issue:`7418`.)
|
|
|
|
* The default :class:`~httplib.HTTPResponse` class used by the :mod:`httplib` module now
|
|
supports buffering, resulting in much faster reading of HTTP responses.
|
|
(Contributed by Kristján Valur Jónsson; :issue:`4879`.)
|
|
|
|
The :class:`~httplib.HTTPConnection` and :class:`~httplib.HTTPSConnection` classes
|
|
now support a *source_address* parameter, a ``(host, port)`` 2-tuple
|
|
giving the source address that will be used for the connection.
|
|
(Contributed by Eldon Ziegler; :issue:`3972`.)
|
|
|
|
* The :mod:`ihooks` module now supports relative imports. Note that
|
|
:mod:`ihooks` is an older module for customizing imports,
|
|
superseded by the :mod:`imputil` module added in Python 2.0.
|
|
(Relative import support added by Neil Schemenauer.)
|
|
|
|
.. revision 75423
|
|
|
|
* The :mod:`imaplib` module now supports IPv6 addresses.
|
|
(Contributed by Derek Morr; :issue:`1655`.)
|
|
|
|
* New function: the :mod:`inspect` module's :func:`~inspect.getcallargs`
|
|
takes a callable and its positional and keyword arguments,
|
|
and figures out which of the callable's parameters will receive each argument,
|
|
returning a dictionary mapping argument names to their values. For example::
|
|
|
|
>>> from inspect import getcallargs
|
|
>>> def f(a, b=1, *pos, **named):
|
|
... pass
|
|
...
|
|
>>> getcallargs(f, 1, 2, 3)
|
|
{'a': 1, 'b': 2, 'pos': (3,), 'named': {}}
|
|
>>> getcallargs(f, a=2, x=4)
|
|
{'a': 2, 'b': 1, 'pos': (), 'named': {'x': 4}}
|
|
>>> getcallargs(f)
|
|
Traceback (most recent call last):
|
|
...
|
|
TypeError: f() takes at least 1 argument (0 given)
|
|
|
|
Contributed by George Sakkis; :issue:`3135`.
|
|
|
|
* Updated module: The :mod:`io` library has been upgraded to the version shipped with
|
|
Python 3.1. For 3.1, the I/O library was entirely rewritten in C
|
|
and is 2 to 20 times faster depending on the task being performed. The
|
|
original Python version was renamed to the :mod:`_pyio` module.
|
|
|
|
One minor resulting change: the :class:`io.TextIOBase` class now
|
|
has an :attr:`errors` attribute giving the error setting
|
|
used for encoding and decoding errors (one of ``'strict'``, ``'replace'``,
|
|
``'ignore'``).
|
|
|
|
The :class:`io.FileIO` class now raises an :exc:`OSError` when passed
|
|
an invalid file descriptor. (Implemented by Benjamin Peterson;
|
|
:issue:`4991`.) The :meth:`~io.IOBase.truncate` method now preserves the
|
|
file position; previously it would change the file position to the
|
|
end of the new file. (Fixed by Pascal Chambon; :issue:`6939`.)
|
|
|
|
* New function: ``itertools.compress(data, selectors)`` takes two
|
|
iterators. Elements of *data* are returned if the corresponding
|
|
value in *selectors* is true::
|
|
|
|
itertools.compress('ABCDEF', [1,0,1,0,1,1]) =>
|
|
A, C, E, F
|
|
|
|
.. maybe here is better to use >>> list(itertools.compress(...)) instead
|
|
|
|
New function: ``itertools.combinations_with_replacement(iter, r)``
|
|
returns all the possible *r*-length combinations of elements from the
|
|
iterable *iter*. Unlike :func:`~itertools.combinations`, individual elements
|
|
can be repeated in the generated combinations::
|
|
|
|
itertools.combinations_with_replacement('abc', 2) =>
|
|
('a', 'a'), ('a', 'b'), ('a', 'c'),
|
|
('b', 'b'), ('b', 'c'), ('c', 'c')
|
|
|
|
Note that elements are treated as unique depending on their position
|
|
in the input, not their actual values.
|
|
|
|
The :func:`itertools.count` function now has a *step* argument that
|
|
allows incrementing by values other than 1. :func:`~itertools.count` also
|
|
now allows keyword arguments, and using non-integer values such as
|
|
floats or :class:`~decimal.Decimal` instances. (Implemented by Raymond
|
|
Hettinger; :issue:`5032`.)
|
|
|
|
:func:`itertools.combinations` and :func:`itertools.product`
|
|
previously raised :exc:`ValueError` for values of *r* larger than
|
|
the input iterable. This was deemed a specification error, so they
|
|
now return an empty iterator. (Fixed by Raymond Hettinger; :issue:`4816`.)
|
|
|
|
* Updated module: The :mod:`json` module was upgraded to version 2.0.9 of the
|
|
simplejson package, which includes a C extension that makes
|
|
encoding and decoding faster.
|
|
(Contributed by Bob Ippolito; :issue:`4136`.)
|
|
|
|
To support the new :class:`collections.OrderedDict` type, :func:`json.load`
|
|
now has an optional *object_pairs_hook* parameter that will be called
|
|
with any object literal that decodes to a list of pairs.
|
|
(Contributed by Raymond Hettinger; :issue:`5381`.)
|
|
|
|
* The :mod:`mailbox` module's :class:`~mailbox.Maildir` class now records the
|
|
timestamp on the directories it reads, and only re-reads them if the
|
|
modification time has subsequently changed. This improves
|
|
performance by avoiding unneeded directory scans. (Fixed by
|
|
A.M. Kuchling and Antoine Pitrou; :issue:`1607951`, :issue:`6896`.)
|
|
|
|
* New functions: the :mod:`math` module gained
|
|
:func:`~math.erf` and :func:`~math.erfc` for the error function and the complementary error function,
|
|
:func:`~math.expm1` which computes ``e**x - 1`` with more precision than
|
|
using :func:`~math.exp` and subtracting 1,
|
|
:func:`~math.gamma` for the Gamma function, and
|
|
:func:`~math.lgamma` for the natural log of the Gamma function.
|
|
(Contributed by Mark Dickinson and nirinA raseliarison; :issue:`3366`.)
|
|
|
|
* The :mod:`multiprocessing` module's :class:`Manager*` classes
|
|
can now be passed a callable that will be called whenever
|
|
a subprocess is started, along with a set of arguments that will be
|
|
passed to the callable.
|
|
(Contributed by lekma; :issue:`5585`.)
|
|
|
|
The :class:`~multiprocessing.Pool` class, which controls a pool of worker processes,
|
|
now has an optional *maxtasksperchild* parameter. Worker processes
|
|
will perform the specified number of tasks and then exit, causing the
|
|
:class:`~multiprocessing.Pool` to start a new worker. This is useful if tasks may leak
|
|
memory or other resources, or if some tasks will cause the worker to
|
|
become very large.
|
|
(Contributed by Charles Cazabon; :issue:`6963`.)
|
|
|
|
* The :mod:`nntplib` module now supports IPv6 addresses.
|
|
(Contributed by Derek Morr; :issue:`1664`.)
|
|
|
|
* New functions: the :mod:`os` module wraps the following POSIX system
|
|
calls: :func:`~os.getresgid` and :func:`~os.getresuid`, which return the
|
|
real, effective, and saved GIDs and UIDs;
|
|
:func:`~os.setresgid` and :func:`~os.setresuid`, which set
|
|
real, effective, and saved GIDs and UIDs to new values;
|
|
:func:`~os.initgroups`, which initialize the group access list
|
|
for the current process. (GID/UID functions
|
|
contributed by Travis H.; :issue:`6508`. Support for initgroups added
|
|
by Jean-Paul Calderone; :issue:`7333`.)
|
|
|
|
The :func:`os.fork` function now re-initializes the import lock in
|
|
the child process; this fixes problems on Solaris when :func:`~os.fork`
|
|
is called from a thread. (Fixed by Zsolt Cserna; :issue:`7242`.)
|
|
|
|
* In the :mod:`os.path` module, the :func:`~os.path.normpath` and
|
|
:func:`~os.path.abspath` functions now preserve Unicode; if their input path
|
|
is a Unicode string, the return value is also a Unicode string.
|
|
(:meth:`~os.path.normpath` fixed by Matt Giuca in :issue:`5827`;
|
|
:meth:`~os.path.abspath` fixed by Ezio Melotti in :issue:`3426`.)
|
|
|
|
* The :mod:`pydoc` module now has help for the various symbols that Python
|
|
uses. You can now do ``help('<<')`` or ``help('@')``, for example.
|
|
(Contributed by David Laban; :issue:`4739`.)
|
|
|
|
* The :mod:`re` module's :func:`~re.split`, :func:`~re.sub`, and :func:`~re.subn`
|
|
now accept an optional *flags* argument, for consistency with the
|
|
other functions in the module. (Added by Gregory P. Smith.)
|
|
|
|
* New function: :func:`~runpy.run_path` in the :mod:`runpy` module
|
|
will execute the code at a provided *path* argument. *path* can be
|
|
the path of a Python source file (:file:`example.py`), a compiled
|
|
bytecode file (:file:`example.pyc`), a directory
|
|
(:file:`./package/`), or a zip archive (:file:`example.zip`). If a
|
|
directory or zip path is provided, it will be added to the front of
|
|
``sys.path`` and the module :mod:`__main__` will be imported. It's
|
|
expected that the directory or zip contains a :file:`__main__.py`;
|
|
if it doesn't, some other :file:`__main__.py` might be imported from
|
|
a location later in ``sys.path``. This makes more of the machinery
|
|
of :mod:`runpy` available to scripts that want to mimic the way
|
|
Python's command line processes an explicit path name.
|
|
(Added by Nick Coghlan; :issue:`6816`.)
|
|
|
|
* New function: in the :mod:`shutil` module, :func:`~shutil.make_archive`
|
|
takes a filename, archive type (zip or tar-format), and a directory
|
|
path, and creates an archive containing the directory's contents.
|
|
(Added by Tarek Ziadé.)
|
|
|
|
:mod:`shutil`'s :func:`~shutil.copyfile` and :func:`~shutil.copytree`
|
|
functions now raise a :exc:`~shutil.SpecialFileError` exception when
|
|
asked to copy a named pipe. Previously the code would treat
|
|
named pipes like a regular file by opening them for reading, and
|
|
this would block indefinitely. (Fixed by Antoine Pitrou; :issue:`3002`.)
|
|
|
|
* The :mod:`signal` module no longer re-installs the signal handler
|
|
unless this is truly necessary, which fixes a bug that could make it
|
|
impossible to catch the EINTR signal robustly. (Fixed by
|
|
Charles-Francois Natali; :issue:`8354`.)
|
|
|
|
* New functions: in the :mod:`site` module, three new functions
|
|
return various site- and user-specific paths.
|
|
:func:`~site.getsitepackages` returns a list containing all
|
|
global site-packages directories,
|
|
:func:`~site.getusersitepackages` returns the path of the user's
|
|
site-packages directory, and
|
|
:func:`~site.getuserbase` returns the value of the :envvar:`USER_BASE`
|
|
environment variable, giving the path to a directory that can be used
|
|
to store data.
|
|
(Contributed by Tarek Ziadé; :issue:`6693`.)
|
|
|
|
The :mod:`site` module now reports exceptions occurring
|
|
when the :mod:`sitecustomize` module is imported, and will no longer
|
|
catch and swallow the :exc:`KeyboardInterrupt` exception. (Fixed by
|
|
Victor Stinner; :issue:`3137`.)
|
|
|
|
* The :func:`~socket.create_connection` function
|
|
gained a *source_address* parameter, a ``(host, port)`` 2-tuple
|
|
giving the source address that will be used for the connection.
|
|
(Contributed by Eldon Ziegler; :issue:`3972`.)
|
|
|
|
The :meth:`~socket.socket.recv_into` and :meth:`~socket.socket.recvfrom_into`
|
|
methods will now write into objects that support the buffer API, most usefully
|
|
the :class:`bytearray` and :class:`memoryview` objects. (Implemented by
|
|
Antoine Pitrou; :issue:`8104`.)
|
|
|
|
* The :mod:`SocketServer` module's :class:`~SocketServer.TCPServer` class now
|
|
supports socket timeouts and disabling the Nagle algorithm.
|
|
The :attr:`~SocketServer.TCPServer.disable_nagle_algorithm` class attribute
|
|
defaults to ``False``; if overridden to be true,
|
|
new request connections will have the TCP_NODELAY option set to
|
|
prevent buffering many small sends into a single TCP packet.
|
|
The :attr:`~SocketServer.BaseServer.timeout` class attribute can hold
|
|
a timeout in seconds that will be applied to the request socket; if
|
|
no request is received within that time, :meth:`~SocketServer.BaseServer.handle_timeout`
|
|
will be called and :meth:`~SocketServer.BaseServer.handle_request` will return.
|
|
(Contributed by Kristján Valur Jónsson; :issue:`6192` and :issue:`6267`.)
|
|
|
|
* Updated module: the :mod:`sqlite3` module has been updated to
|
|
version 2.6.0 of the `pysqlite package <https://github.com/ghaering/pysqlite>`__. Version 2.6.0 includes a number of bugfixes, and adds
|
|
the ability to load SQLite extensions from shared libraries.
|
|
Call the ``enable_load_extension(True)`` method to enable extensions,
|
|
and then call :meth:`~sqlite3.Connection.load_extension` to load a particular shared library.
|
|
(Updated by Gerhard Häring.)
|
|
|
|
* The :mod:`ssl` module's :class:`~ssl.SSLSocket` objects now support the
|
|
buffer API, which fixed a test suite failure (fix by Antoine Pitrou;
|
|
:issue:`7133`) and automatically set
|
|
OpenSSL's :c:macro:`SSL_MODE_AUTO_RETRY`, which will prevent an error
|
|
code being returned from :meth:`recv` operations that trigger an SSL
|
|
renegotiation (fix by Antoine Pitrou; :issue:`8222`).
|
|
|
|
The :func:`ssl.wrap_socket` constructor function now takes a
|
|
*ciphers* argument that's a string listing the encryption algorithms
|
|
to be allowed; the format of the string is described
|
|
`in the OpenSSL documentation
|
|
<https://www.openssl.org/docs/man1.0.2/man1/ciphers.html>`__.
|
|
(Added by Antoine Pitrou; :issue:`8322`.)
|
|
|
|
Another change makes the extension load all of OpenSSL's ciphers and
|
|
digest algorithms so that they're all available. Some SSL
|
|
certificates couldn't be verified, reporting an "unknown algorithm"
|
|
error. (Reported by Beda Kosata, and fixed by Antoine Pitrou;
|
|
:issue:`8484`.)
|
|
|
|
The version of OpenSSL being used is now available as the module
|
|
attributes :data:`ssl.OPENSSL_VERSION` (a string),
|
|
:data:`ssl.OPENSSL_VERSION_INFO` (a 5-tuple), and
|
|
:data:`ssl.OPENSSL_VERSION_NUMBER` (an integer). (Added by Antoine
|
|
Pitrou; :issue:`8321`.)
|
|
|
|
* The :mod:`struct` module will no longer silently ignore overflow
|
|
errors when a value is too large for a particular integer format
|
|
code (one of ``bBhHiIlLqQ``); it now always raises a
|
|
:exc:`struct.error` exception. (Changed by Mark Dickinson;
|
|
:issue:`1523`.) The :func:`~struct.pack` function will also
|
|
attempt to use :meth:`__index__` to convert and pack non-integers
|
|
before trying the :meth:`__int__` method or reporting an error.
|
|
(Changed by Mark Dickinson; :issue:`8300`.)
|
|
|
|
* New function: the :mod:`subprocess` module's
|
|
:func:`~subprocess.check_output` runs a command with a specified set of arguments
|
|
and returns the command's output as a string when the command runs without
|
|
error, or raises a :exc:`~subprocess.CalledProcessError` exception otherwise.
|
|
|
|
::
|
|
|
|
>>> subprocess.check_output(['df', '-h', '.'])
|
|
'Filesystem Size Used Avail Capacity Mounted on\n
|
|
/dev/disk0s2 52G 49G 3.0G 94% /\n'
|
|
|
|
>>> subprocess.check_output(['df', '-h', '/bogus'])
|
|
...
|
|
subprocess.CalledProcessError: Command '['df', '-h', '/bogus']' returned non-zero exit status 1
|
|
|
|
(Contributed by Gregory P. Smith.)
|
|
|
|
The :mod:`subprocess` module will now retry its internal system calls
|
|
on receiving an :const:`EINTR` signal. (Reported by several people; final
|
|
patch by Gregory P. Smith in :issue:`1068268`.)
|
|
|
|
* New function: :func:`~symtable.Symbol.is_declared_global` in the :mod:`symtable` module
|
|
returns true for variables that are explicitly declared to be global,
|
|
false for ones that are implicitly global.
|
|
(Contributed by Jeremy Hylton.)
|
|
|
|
* The :mod:`syslog` module will now use the value of ``sys.argv[0]`` as the
|
|
identifier instead of the previous default value of ``'python'``.
|
|
(Changed by Sean Reifschneider; :issue:`8451`.)
|
|
|
|
* The ``sys.version_info`` value is now a named tuple, with attributes
|
|
named :attr:`major`, :attr:`minor`, :attr:`micro`,
|
|
:attr:`releaselevel`, and :attr:`serial`. (Contributed by Ross
|
|
Light; :issue:`4285`.)
|
|
|
|
:func:`sys.getwindowsversion` also returns a named tuple,
|
|
with attributes named :attr:`major`, :attr:`minor`, :attr:`build`,
|
|
:attr:`platform`, :attr:`service_pack`, :attr:`service_pack_major`,
|
|
:attr:`service_pack_minor`, :attr:`suite_mask`, and
|
|
:attr:`product_type`. (Contributed by Brian Curtin; :issue:`7766`.)
|
|
|
|
* The :mod:`tarfile` module's default error handling has changed, to
|
|
no longer suppress fatal errors. The default error level was previously 0,
|
|
which meant that errors would only result in a message being written to the
|
|
debug log, but because the debug log is not activated by default,
|
|
these errors go unnoticed. The default error level is now 1,
|
|
which raises an exception if there's an error.
|
|
(Changed by Lars Gustäbel; :issue:`7357`.)
|
|
|
|
:mod:`tarfile` now supports filtering the :class:`~tarfile.TarInfo`
|
|
objects being added to a tar file. When you call :meth:`~tarfile.TarFile.add`,
|
|
you may supply an optional *filter* argument
|
|
that's a callable. The *filter* callable will be passed the
|
|
:class:`~tarfile.TarInfo` for every file being added, and can modify and return it.
|
|
If the callable returns ``None``, the file will be excluded from the
|
|
resulting archive. This is more powerful than the existing
|
|
*exclude* argument, which has therefore been deprecated.
|
|
(Added by Lars Gustäbel; :issue:`6856`.)
|
|
The :class:`~tarfile.TarFile` class also now supports the context management protocol.
|
|
(Added by Lars Gustäbel; :issue:`7232`.)
|
|
|
|
* The :meth:`~threading.Event.wait` method of the :class:`threading.Event` class
|
|
now returns the internal flag on exit. This means the method will usually
|
|
return true because :meth:`~threading.Event.wait` is supposed to block until the
|
|
internal flag becomes true. The return value will only be false if
|
|
a timeout was provided and the operation timed out.
|
|
(Contributed by Tim Lesher; :issue:`1674032`.)
|
|
|
|
* The Unicode database provided by the :mod:`unicodedata` module is
|
|
now used internally to determine which characters are numeric,
|
|
whitespace, or represent line breaks. The database also
|
|
includes information from the :file:`Unihan.txt` data file (patch
|
|
by Anders Chrigström and Amaury Forgeot d'Arc; :issue:`1571184`)
|
|
and has been updated to version 5.2.0 (updated by
|
|
Florent Xicluna; :issue:`8024`).
|
|
|
|
* The :mod:`urlparse` module's :func:`~urlparse.urlsplit` now handles
|
|
unknown URL schemes in a fashion compliant with :rfc:`3986`: if the
|
|
URL is of the form ``"<something>://..."``, the text before the
|
|
``://`` is treated as the scheme, even if it's a made-up scheme that
|
|
the module doesn't know about. This change may break code that
|
|
worked around the old behaviour. For example, Python 2.6.4 or 2.5
|
|
will return the following:
|
|
|
|
.. doctest::
|
|
:options: +SKIP
|
|
|
|
>>> import urlparse
|
|
>>> urlparse.urlsplit('invented://host/filename?query')
|
|
('invented', '', '//host/filename?query', '', '')
|
|
|
|
Python 2.7 (and Python 2.6.5) will return:
|
|
|
|
.. doctest::
|
|
:options: +SKIP
|
|
|
|
>>> import urlparse
|
|
>>> urlparse.urlsplit('invented://host/filename?query')
|
|
('invented', 'host', '/filename?query', '', '')
|
|
|
|
(Python 2.7 actually produces slightly different output, since it
|
|
returns a named tuple instead of a standard tuple.)
|
|
|
|
The :mod:`urlparse` module also supports IPv6 literal addresses as defined by
|
|
:rfc:`2732` (contributed by Senthil Kumaran; :issue:`2987`).
|
|
|
|
.. doctest::
|
|
:options: +SKIP
|
|
|
|
>>> urlparse.urlparse('http://[1080::8:800:200C:417A]/foo')
|
|
ParseResult(scheme='http', netloc='[1080::8:800:200C:417A]',
|
|
path='/foo', params='', query='', fragment='')
|
|
|
|
* New class: the :class:`~weakref.WeakSet` class in the :mod:`weakref`
|
|
module is a set that only holds weak references to its elements; elements
|
|
will be removed once there are no references pointing to them.
|
|
(Originally implemented in Python 3.x by Raymond Hettinger, and backported
|
|
to 2.7 by Michael Foord.)
|
|
|
|
* The ElementTree library, :mod:`xml.etree`, no longer escapes
|
|
ampersands and angle brackets when outputting an XML processing
|
|
instruction (which looks like ``<?xml-stylesheet href="#style1"?>``)
|
|
or comment (which looks like ``<!-- comment -->``).
|
|
(Patch by Neil Muller; :issue:`2746`.)
|
|
|
|
* The XML-RPC client and server, provided by the :mod:`xmlrpclib` and
|
|
:mod:`SimpleXMLRPCServer` modules, have improved performance by
|
|
supporting HTTP/1.1 keep-alive and by optionally using gzip encoding
|
|
to compress the XML being exchanged. The gzip compression is
|
|
controlled by the :attr:`encode_threshold` attribute of
|
|
:class:`SimpleXMLRPCRequestHandler`, which contains a size in bytes;
|
|
responses larger than this will be compressed.
|
|
(Contributed by Kristján Valur Jónsson; :issue:`6267`.)
|
|
|
|
* The :mod:`zipfile` module's :class:`~zipfile.ZipFile` now supports the context
|
|
management protocol, so you can write ``with zipfile.ZipFile(...) as f:``.
|
|
(Contributed by Brian Curtin; :issue:`5511`.)
|
|
|
|
:mod:`zipfile` now also supports archiving empty directories and
|
|
extracts them correctly. (Fixed by Kuba Wieczorek; :issue:`4710`.)
|
|
Reading files out of an archive is faster, and interleaving
|
|
:meth:`~zipfile.ZipFile.read` and :meth:`~zipfile.ZipFile.readline` now works correctly.
|
|
(Contributed by Nir Aides; :issue:`7610`.)
|
|
|
|
The :func:`~zipfile.is_zipfile` function now
|
|
accepts a file object, in addition to the path names accepted in earlier
|
|
versions. (Contributed by Gabriel Genellina; :issue:`4756`.)
|
|
|
|
The :meth:`~zipfile.ZipFile.writestr` method now has an optional *compress_type* parameter
|
|
that lets you override the default compression method specified in the
|
|
:class:`~zipfile.ZipFile` constructor. (Contributed by Ronald Oussoren;
|
|
:issue:`6003`.)
|
|
|
|
|
|
.. ======================================================================
|
|
.. whole new modules get described in subsections here
|
|
|
|
|
|
.. _importlib-section:
|
|
|
|
New module: importlib
|
|
------------------------------
|
|
|
|
Python 3.1 includes the :mod:`importlib` package, a re-implementation
|
|
of the logic underlying Python's :keyword:`import` statement.
|
|
:mod:`importlib` is useful for implementors of Python interpreters and
|
|
to users who wish to write new importers that can participate in the
|
|
import process. Python 2.7 doesn't contain the complete
|
|
:mod:`importlib` package, but instead has a tiny subset that contains
|
|
a single function, :func:`~importlib.import_module`.
|
|
|
|
``import_module(name, package=None)`` imports a module. *name* is
|
|
a string containing the module or package's name. It's possible to do
|
|
relative imports by providing a string that begins with a ``.``
|
|
character, such as ``..utils.errors``. For relative imports, the
|
|
*package* argument must be provided and is the name of the package that
|
|
will be used as the anchor for
|
|
the relative import. :func:`~importlib.import_module` both inserts the imported
|
|
module into ``sys.modules`` and returns the module object.
|
|
|
|
Here are some examples::
|
|
|
|
>>> from importlib import import_module
|
|
>>> anydbm = import_module('anydbm') # Standard absolute import
|
|
>>> anydbm
|
|
<module 'anydbm' from '/p/python/Lib/anydbm.py'>
|
|
>>> # Relative import
|
|
>>> file_util = import_module('..file_util', 'distutils.command')
|
|
>>> file_util
|
|
<module 'distutils.file_util' from '/python/Lib/distutils/file_util.pyc'>
|
|
|
|
:mod:`importlib` was implemented by Brett Cannon and introduced in
|
|
Python 3.1.
|
|
|
|
|
|
New module: sysconfig
|
|
---------------------------------
|
|
|
|
The :mod:`sysconfig` module has been pulled out of the Distutils
|
|
package, becoming a new top-level module in its own right.
|
|
:mod:`sysconfig` provides functions for getting information about
|
|
Python's build process: compiler switches, installation paths, the
|
|
platform name, and whether Python is running from its source
|
|
directory.
|
|
|
|
Some of the functions in the module are:
|
|
|
|
* :func:`~sysconfig.get_config_var` returns variables from Python's
|
|
Makefile and the :file:`pyconfig.h` file.
|
|
* :func:`~sysconfig.get_config_vars` returns a dictionary containing
|
|
all of the configuration variables.
|
|
* :func:`~sysconfig.get_path` returns the configured path for
|
|
a particular type of module: the standard library,
|
|
site-specific modules, platform-specific modules, etc.
|
|
* :func:`~sysconfig.is_python_build` returns true if you're running a
|
|
binary from a Python source tree, and false otherwise.
|
|
|
|
Consult the :mod:`sysconfig` documentation for more details and for
|
|
a complete list of functions.
|
|
|
|
The Distutils package and :mod:`sysconfig` are now maintained by Tarek
|
|
Ziadé, who has also started a Distutils2 package (source repository at
|
|
https://hg.python.org/distutils2/) for developing a next-generation
|
|
version of Distutils.
|
|
|
|
|
|
ttk: Themed Widgets for Tk
|
|
--------------------------
|
|
|
|
Tcl/Tk 8.5 includes a set of themed widgets that re-implement basic Tk
|
|
widgets but have a more customizable appearance and can therefore more
|
|
closely resemble the native platform's widgets. This widget
|
|
set was originally called Tile, but was renamed to Ttk (for "themed Tk")
|
|
on being added to Tcl/Tck release 8.5.
|
|
|
|
To learn more, read the :mod:`ttk` module documentation. You may also
|
|
wish to read the Tcl/Tk manual page describing the
|
|
Ttk theme engine, available at
|
|
https://www.tcl.tk/man/tcl8.5/TkCmd/ttk_intro.htm. Some
|
|
screenshots of the Python/Ttk code in use are at
|
|
https://code.google.com/archive/p/python-ttk/wikis/Screenshots.wiki.
|
|
|
|
The :mod:`ttk` module was written by Guilherme Polo and added in
|
|
:issue:`2983`. An alternate version called ``Tile.py``, written by
|
|
Martin Franklin and maintained by Kevin Walzer, was proposed for
|
|
inclusion in :issue:`2618`, but the authors argued that Guilherme
|
|
Polo's work was more comprehensive.
|
|
|
|
|
|
.. _unittest-section:
|
|
|
|
Updated module: unittest
|
|
---------------------------------
|
|
|
|
The :mod:`unittest` module was greatly enhanced; many
|
|
new features were added. Most of these features were implemented
|
|
by Michael Foord, unless otherwise noted. The enhanced version of
|
|
the module is downloadable separately for use with Python versions 2.4 to 2.6,
|
|
packaged as the :mod:`unittest2` package, from
|
|
https://pypi.org/project/unittest2.
|
|
|
|
When used from the command line, the module can automatically discover
|
|
tests. It's not as fancy as `py.test <https://pytest.org>`__ or
|
|
`nose <https://nose.readthedocs.io/>`__, but provides a
|
|
simple way to run tests kept within a set of package directories. For example,
|
|
the following command will search the :file:`test/` subdirectory for
|
|
any importable test files named ``test*.py``::
|
|
|
|
python -m unittest discover -s test
|
|
|
|
Consult the :mod:`unittest` module documentation for more details.
|
|
(Developed in :issue:`6001`.)
|
|
|
|
The :func:`~unittest.main` function supports some other new options:
|
|
|
|
* :option:`-b <unittest -b>` or :option:`!--buffer` will buffer the standard output
|
|
and standard error streams during each test. If the test passes,
|
|
any resulting output will be discarded; on failure, the buffered
|
|
output will be displayed.
|
|
|
|
* :option:`-c <unittest -c>` or :option:`!--catch` will cause the control-C interrupt
|
|
to be handled more gracefully. Instead of interrupting the test
|
|
process immediately, the currently running test will be completed
|
|
and then the partial results up to the interruption will be reported.
|
|
If you're impatient, a second press of control-C will cause an immediate
|
|
interruption.
|
|
|
|
This control-C handler tries to avoid causing problems when the code
|
|
being tested or the tests being run have defined a signal handler of
|
|
their own, by noticing that a signal handler was already set and
|
|
calling it. If this doesn't work for you, there's a
|
|
:func:`~unittest.removeHandler` decorator that can be used to mark tests that
|
|
should have the control-C handling disabled.
|
|
|
|
* :option:`-f <unittest -f>` or :option:`!--failfast` makes
|
|
test execution stop immediately when a test fails instead of
|
|
continuing to execute further tests. (Suggested by Cliff Dyer and
|
|
implemented by Michael Foord; :issue:`8074`.)
|
|
|
|
The progress messages now show 'x' for expected failures
|
|
and 'u' for unexpected successes when run in verbose mode.
|
|
(Contributed by Benjamin Peterson.)
|
|
|
|
Test cases can raise the :exc:`~unittest.SkipTest` exception to skip a
|
|
test (:issue:`1034053`).
|
|
|
|
The error messages for :meth:`~unittest.TestCase.assertEqual`,
|
|
:meth:`~unittest.TestCase.assertTrue`, and :meth:`~unittest.TestCase.assertFalse`
|
|
failures now provide more information. If you set the
|
|
:attr:`~unittest.TestCase.longMessage` attribute of your :class:`~unittest.TestCase` classes to
|
|
true, both the standard error message and any additional message you
|
|
provide will be printed for failures. (Added by Michael Foord; :issue:`5663`.)
|
|
|
|
The :meth:`~unittest.TestCase.assertRaises` method now
|
|
returns a context handler when called without providing a callable
|
|
object to run. For example, you can write this::
|
|
|
|
with self.assertRaises(KeyError):
|
|
{}['foo']
|
|
|
|
(Implemented by Antoine Pitrou; :issue:`4444`.)
|
|
|
|
.. rev 78774
|
|
|
|
Module- and class-level setup and teardown fixtures are now supported.
|
|
Modules can contain :func:`~unittest.setUpModule` and :func:`~unittest.tearDownModule`
|
|
functions. Classes can have :meth:`~unittest.TestCase.setUpClass` and
|
|
:meth:`~unittest.TestCase.tearDownClass` methods that must be defined as class methods
|
|
(using ``@classmethod`` or equivalent). These functions and
|
|
methods are invoked when the test runner switches to a test case in a
|
|
different module or class.
|
|
|
|
The methods :meth:`~unittest.TestCase.addCleanup` and
|
|
:meth:`~unittest.TestCase.doCleanups` were added.
|
|
:meth:`~unittest.TestCase.addCleanup` lets you add cleanup functions that
|
|
will be called unconditionally (after :meth:`~unittest.TestCase.setUp` if
|
|
:meth:`~unittest.TestCase.setUp` fails, otherwise after :meth:`~unittest.TestCase.tearDown`). This allows
|
|
for much simpler resource allocation and deallocation during tests
|
|
(:issue:`5679`).
|
|
|
|
A number of new methods were added that provide more specialized
|
|
tests. Many of these methods were written by Google engineers
|
|
for use in their test suites; Gregory P. Smith, Michael Foord, and
|
|
GvR worked on merging them into Python's version of :mod:`unittest`.
|
|
|
|
* :meth:`~unittest.TestCase.assertIsNone` and :meth:`~unittest.TestCase.assertIsNotNone` take one
|
|
expression and verify that the result is or is not ``None``.
|
|
|
|
* :meth:`~unittest.TestCase.assertIs` and :meth:`~unittest.TestCase.assertIsNot`
|
|
take two values and check whether the two values evaluate to the same object or not.
|
|
(Added by Michael Foord; :issue:`2578`.)
|
|
|
|
* :meth:`~unittest.TestCase.assertIsInstance` and
|
|
:meth:`~unittest.TestCase.assertNotIsInstance` check whether
|
|
the resulting object is an instance of a particular class, or of
|
|
one of a tuple of classes. (Added by Georg Brandl; :issue:`7031`.)
|
|
|
|
* :meth:`~unittest.TestCase.assertGreater`, :meth:`~unittest.TestCase.assertGreaterEqual`,
|
|
:meth:`~unittest.TestCase.assertLess`, and :meth:`~unittest.TestCase.assertLessEqual` compare
|
|
two quantities.
|
|
|
|
* :meth:`~unittest.TestCase.assertMultiLineEqual` compares two strings, and if they're
|
|
not equal, displays a helpful comparison that highlights the
|
|
differences in the two strings. This comparison is now used by
|
|
default when Unicode strings are compared with :meth:`~unittest.TestCase.assertEqual`.
|
|
|
|
* :meth:`~unittest.TestCase.assertRegexpMatches` and
|
|
:meth:`~unittest.TestCase.assertNotRegexpMatches` checks whether the
|
|
first argument is a string matching or not matching the regular
|
|
expression provided as the second argument (:issue:`8038`).
|
|
|
|
* :meth:`~unittest.TestCase.assertRaisesRegexp` checks whether a particular exception
|
|
is raised, and then also checks that the string representation of
|
|
the exception matches the provided regular expression.
|
|
|
|
* :meth:`~unittest.TestCase.assertIn` and :meth:`~unittest.TestCase.assertNotIn`
|
|
tests whether *first* is or is not in *second*.
|
|
|
|
* :meth:`~unittest.TestCase.assertItemsEqual` tests whether two provided sequences
|
|
contain the same elements.
|
|
|
|
* :meth:`~unittest.TestCase.assertSetEqual` compares whether two sets are equal, and
|
|
only reports the differences between the sets in case of error.
|
|
|
|
* Similarly, :meth:`~unittest.TestCase.assertListEqual` and :meth:`~unittest.TestCase.assertTupleEqual`
|
|
compare the specified types and explain any differences without necessarily
|
|
printing their full values; these methods are now used by default
|
|
when comparing lists and tuples using :meth:`~unittest.TestCase.assertEqual`.
|
|
More generally, :meth:`~unittest.TestCase.assertSequenceEqual` compares two sequences
|
|
and can optionally check whether both sequences are of a
|
|
particular type.
|
|
|
|
* :meth:`~unittest.TestCase.assertDictEqual` compares two dictionaries and reports the
|
|
differences; it's now used by default when you compare two dictionaries
|
|
using :meth:`~unittest.TestCase.assertEqual`. :meth:`~unittest.TestCase.assertDictContainsSubset` checks whether
|
|
all of the key/value pairs in *first* are found in *second*.
|
|
|
|
* :meth:`~unittest.TestCase.assertAlmostEqual` and :meth:`~unittest.TestCase.assertNotAlmostEqual` test
|
|
whether *first* and *second* are approximately equal. This method
|
|
can either round their difference to an optionally specified number
|
|
of *places* (the default is 7) and compare it to zero, or require
|
|
the difference to be smaller than a supplied *delta* value.
|
|
|
|
* :meth:`~unittest.TestLoader.loadTestsFromName` properly honors the
|
|
:attr:`~unittest.TestLoader.suiteClass` attribute of
|
|
the :class:`~unittest.TestLoader`. (Fixed by Mark Roddy; :issue:`6866`.)
|
|
|
|
* A new hook lets you extend the :meth:`~unittest.TestCase.assertEqual` method to handle
|
|
new data types. The :meth:`~unittest.TestCase.addTypeEqualityFunc` method takes a type
|
|
object and a function. The function will be used when both of the
|
|
objects being compared are of the specified type. This function
|
|
should compare the two objects and raise an exception if they don't
|
|
match; it's a good idea for the function to provide additional
|
|
information about why the two objects aren't matching, much as the new
|
|
sequence comparison methods do.
|
|
|
|
:func:`unittest.main` now takes an optional ``exit`` argument. If
|
|
false, :func:`~unittest.main` doesn't call :func:`sys.exit`, allowing
|
|
:func:`~unittest.main` to be used from the interactive interpreter.
|
|
(Contributed by J. Pablo Fernández; :issue:`3379`.)
|
|
|
|
:class:`~unittest.TestResult` has new :meth:`~unittest.TestResult.startTestRun` and
|
|
:meth:`~unittest.TestResult.stopTestRun` methods that are called immediately before
|
|
and after a test run. (Contributed by Robert Collins; :issue:`5728`.)
|
|
|
|
With all these changes, the :file:`unittest.py` was becoming awkwardly
|
|
large, so the module was turned into a package and the code split into
|
|
several files (by Benjamin Peterson). This doesn't affect how the
|
|
module is imported or used.
|
|
|
|
.. seealso::
|
|
|
|
https://web.archive.org/web/20210619163128/http://www.voidspace.org.uk/python/articles/unittest2.shtml
|
|
Describes the new features, how to use them, and the
|
|
rationale for various design decisions. (By Michael Foord.)
|
|
|
|
.. _elementtree-section:
|
|
|
|
Updated module: ElementTree 1.3
|
|
---------------------------------
|
|
|
|
The version of the ElementTree library included with Python was updated to
|
|
version 1.3. Some of the new features are:
|
|
|
|
* The various parsing functions now take a *parser* keyword argument
|
|
giving an :class:`~xml.etree.ElementTree.XMLParser` instance that will
|
|
be used. This makes it possible to override the file's internal encoding::
|
|
|
|
p = ET.XMLParser(encoding='utf-8')
|
|
t = ET.XML("""<root/>""", parser=p)
|
|
|
|
Errors in parsing XML now raise a :exc:`ParseError` exception, whose
|
|
instances have a :attr:`position` attribute
|
|
containing a (*line*, *column*) tuple giving the location of the problem.
|
|
|
|
* ElementTree's code for converting trees to a string has been
|
|
significantly reworked, making it roughly twice as fast in many
|
|
cases. The :meth:`ElementTree.write() <xml.etree.ElementTree.ElementTree.write>`
|
|
and :meth:`Element.write` methods now have a *method* parameter that can be
|
|
"xml" (the default), "html", or "text". HTML mode will output empty
|
|
elements as ``<empty></empty>`` instead of ``<empty/>``, and text
|
|
mode will skip over elements and only output the text chunks. If
|
|
you set the :attr:`tag` attribute of an element to ``None`` but
|
|
leave its children in place, the element will be omitted when the
|
|
tree is written out, so you don't need to do more extensive rearrangement
|
|
to remove a single element.
|
|
|
|
Namespace handling has also been improved. All ``xmlns:<whatever>``
|
|
declarations are now output on the root element, not scattered throughout
|
|
the resulting XML. You can set the default namespace for a tree
|
|
by setting the :attr:`default_namespace` attribute and can
|
|
register new prefixes with :meth:`~xml.etree.ElementTree.register_namespace`. In XML mode,
|
|
you can use the true/false *xml_declaration* parameter to suppress the
|
|
XML declaration.
|
|
|
|
* New :class:`~xml.etree.ElementTree.Element` method:
|
|
:meth:`~xml.etree.ElementTree.Element.extend` appends the items from a
|
|
sequence to the element's children. Elements themselves behave like
|
|
sequences, so it's easy to move children from one element to
|
|
another::
|
|
|
|
from xml.etree import ElementTree as ET
|
|
|
|
t = ET.XML("""<list>
|
|
<item>1</item> <item>2</item> <item>3</item>
|
|
</list>""")
|
|
new = ET.XML('<root/>')
|
|
new.extend(t)
|
|
|
|
# Outputs <root><item>1</item>...</root>
|
|
print ET.tostring(new)
|
|
|
|
* New :class:`Element` method:
|
|
:meth:`~xml.etree.ElementTree.Element.iter` yields the children of the
|
|
element as a generator. It's also possible to write ``for child in
|
|
elem:`` to loop over an element's children. The existing method
|
|
:meth:`getiterator` is now deprecated, as is :meth:`getchildren`
|
|
which constructs and returns a list of children.
|
|
|
|
* New :class:`Element` method:
|
|
:meth:`~xml.etree.ElementTree.Element.itertext` yields all chunks of
|
|
text that are descendants of the element. For example::
|
|
|
|
t = ET.XML("""<list>
|
|
<item>1</item> <item>2</item> <item>3</item>
|
|
</list>""")
|
|
|
|
# Outputs ['\n ', '1', ' ', '2', ' ', '3', '\n']
|
|
print list(t.itertext())
|
|
|
|
* Deprecated: using an element as a Boolean (i.e., ``if elem:``) would
|
|
return true if the element had any children, or false if there were
|
|
no children. This behaviour is confusing -- ``None`` is false, but
|
|
so is a childless element? -- so it will now trigger a
|
|
:exc:`FutureWarning`. In your code, you should be explicit: write
|
|
``len(elem) != 0`` if you're interested in the number of children,
|
|
or ``elem is not None``.
|
|
|
|
Fredrik Lundh develops ElementTree and produced the 1.3 version;
|
|
you can read his article describing 1.3 at
|
|
https://web.archive.org/web/20200703234532/http://effbot.org/zone/elementtree-13-intro.htm.
|
|
Florent Xicluna updated the version included with
|
|
Python, after discussions on python-dev and in :issue:`6472`.)
|
|
|
|
.. ======================================================================
|
|
|
|
|
|
Build and C API Changes
|
|
=======================
|
|
|
|
Changes to Python's build process and to the C API include:
|
|
|
|
* The latest release of the GNU Debugger, GDB 7, can be `scripted
|
|
using Python
|
|
<https://web.archive.org/web/20110715084810/http://sourceware.org/gdb/current/onlinedocs/gdb/Python.html>`__.
|
|
When you begin debugging an executable program P, GDB will look for
|
|
a file named ``P-gdb.py`` and automatically read it. Dave Malcolm
|
|
contributed a :file:`python-gdb.py` that adds a number of
|
|
commands useful when debugging Python itself. For example,
|
|
``py-up`` and ``py-down`` go up or down one Python stack frame,
|
|
which usually corresponds to several C stack frames. ``py-print``
|
|
prints the value of a Python variable, and ``py-bt`` prints the
|
|
Python stack trace. (Added as a result of :issue:`8032`.)
|
|
|
|
* If you use the :file:`.gdbinit` file provided with Python,
|
|
the "pyo" macro in the 2.7 version now works correctly when the thread being
|
|
debugged doesn't hold the GIL; the macro now acquires it before printing.
|
|
(Contributed by Victor Stinner; :issue:`3632`.)
|
|
|
|
* :c:func:`Py_AddPendingCall` is now thread-safe, letting any
|
|
worker thread submit notifications to the main Python thread. This
|
|
is particularly useful for asynchronous IO operations.
|
|
(Contributed by Kristján Valur Jónsson; :issue:`4293`.)
|
|
|
|
* New function: :c:func:`PyCode_NewEmpty` creates an empty code object;
|
|
only the filename, function name, and first line number are required.
|
|
This is useful for extension modules that are attempting to
|
|
construct a more useful traceback stack. Previously such
|
|
extensions needed to call :c:func:`PyCode_New`, which had many
|
|
more arguments. (Added by Jeffrey Yasskin.)
|
|
|
|
* New function: :c:func:`PyErr_NewExceptionWithDoc` creates a new
|
|
exception class, just as the existing :c:func:`PyErr_NewException` does,
|
|
but takes an extra ``char *`` argument containing the docstring for the
|
|
new exception class. (Added by 'lekma' on the Python bug tracker;
|
|
:issue:`7033`.)
|
|
|
|
* New function: :c:func:`PyFrame_GetLineNumber` takes a frame object
|
|
and returns the line number that the frame is currently executing.
|
|
Previously code would need to get the index of the bytecode
|
|
instruction currently executing, and then look up the line number
|
|
corresponding to that address. (Added by Jeffrey Yasskin.)
|
|
|
|
* New functions: :c:func:`PyLong_AsLongAndOverflow` and
|
|
:c:func:`PyLong_AsLongLongAndOverflow` approximates a Python long
|
|
integer as a C :c:expr:`long` or :c:expr:`long long`.
|
|
If the number is too large to fit into
|
|
the output type, an *overflow* flag is set and returned to the caller.
|
|
(Contributed by Case Van Horsen; :issue:`7528` and :issue:`7767`.)
|
|
|
|
* New function: stemming from the rewrite of string-to-float conversion,
|
|
a new :c:func:`PyOS_string_to_double` function was added. The old
|
|
:c:func:`PyOS_ascii_strtod` and :c:func:`PyOS_ascii_atof` functions
|
|
are now deprecated.
|
|
|
|
* New function: :c:func:`PySys_SetArgvEx` sets the value of
|
|
``sys.argv`` and can optionally update ``sys.path`` to include the
|
|
directory containing the script named by ``sys.argv[0]`` depending
|
|
on the value of an *updatepath* parameter.
|
|
|
|
This function was added to close a security hole for applications
|
|
that embed Python. The old function, :c:func:`PySys_SetArgv`, would
|
|
always update ``sys.path``, and sometimes it would add the current
|
|
directory. This meant that, if you ran an application embedding
|
|
Python in a directory controlled by someone else, attackers could
|
|
put a Trojan-horse module in the directory (say, a file named
|
|
:file:`os.py`) that your application would then import and run.
|
|
|
|
If you maintain a C/C++ application that embeds Python, check
|
|
whether you're calling :c:func:`PySys_SetArgv` and carefully consider
|
|
whether the application should be using :c:func:`PySys_SetArgvEx`
|
|
with *updatepath* set to false.
|
|
|
|
Security issue reported as `CVE-2008-5983
|
|
<https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-5983>`_;
|
|
discussed in :issue:`5753`, and fixed by Antoine Pitrou.
|
|
|
|
* New macros: the Python header files now define the following macros:
|
|
:c:macro:`Py_ISALNUM`,
|
|
:c:macro:`Py_ISALPHA`,
|
|
:c:macro:`Py_ISDIGIT`,
|
|
:c:macro:`Py_ISLOWER`,
|
|
:c:macro:`Py_ISSPACE`,
|
|
:c:macro:`Py_ISUPPER`,
|
|
:c:macro:`Py_ISXDIGIT`,
|
|
:c:macro:`Py_TOLOWER`, and :c:macro:`Py_TOUPPER`.
|
|
All of these functions are analogous to the C
|
|
standard macros for classifying characters, but ignore the current
|
|
locale setting, because in
|
|
several places Python needs to analyze characters in a
|
|
locale-independent way. (Added by Eric Smith;
|
|
:issue:`5793`.)
|
|
|
|
.. XXX these macros don't seem to be described in the c-api docs.
|
|
|
|
* Removed function: :c:macro:`PyEval_CallObject` is now only available
|
|
as a macro. A function version was being kept around to preserve
|
|
ABI linking compatibility, but that was in 1997; it can certainly be
|
|
deleted by now. (Removed by Antoine Pitrou; :issue:`8276`.)
|
|
|
|
* New format codes: the :c:func:`PyFormat_FromString`,
|
|
:c:func:`PyFormat_FromStringV`, and :c:func:`PyErr_Format` functions now
|
|
accept ``%lld`` and ``%llu`` format codes for displaying
|
|
C's :c:expr:`long long` types.
|
|
(Contributed by Mark Dickinson; :issue:`7228`.)
|
|
|
|
* The complicated interaction between threads and process forking has
|
|
been changed. Previously, the child process created by
|
|
:func:`os.fork` might fail because the child is created with only a
|
|
single thread running, the thread performing the :func:`os.fork`.
|
|
If other threads were holding a lock, such as Python's import lock,
|
|
when the fork was performed, the lock would still be marked as
|
|
"held" in the new process. But in the child process nothing would
|
|
ever release the lock, since the other threads weren't replicated,
|
|
and the child process would no longer be able to perform imports.
|
|
|
|
Python 2.7 acquires the import lock before performing an
|
|
:func:`os.fork`, and will also clean up any locks created using the
|
|
:mod:`threading` module. C extension modules that have internal
|
|
locks, or that call :c:func:`fork()` themselves, will not benefit
|
|
from this clean-up.
|
|
|
|
(Fixed by Thomas Wouters; :issue:`1590864`.)
|
|
|
|
* The :c:func:`Py_Finalize` function now calls the internal
|
|
:func:`threading._shutdown` function; this prevents some exceptions from
|
|
being raised when an interpreter shuts down.
|
|
(Patch by Adam Olsen; :issue:`1722344`.)
|
|
|
|
* When using the :c:type:`PyMemberDef` structure to define attributes
|
|
of a type, Python will no longer let you try to delete or set a
|
|
:const:`T_STRING_INPLACE` attribute.
|
|
|
|
.. rev 79644
|
|
|
|
* Global symbols defined by the :mod:`ctypes` module are now prefixed
|
|
with ``Py``, or with ``_ctypes``. (Implemented by Thomas
|
|
Heller; :issue:`3102`.)
|
|
|
|
* New configure option: the :option:`!--with-system-expat` switch allows
|
|
building the :mod:`pyexpat` module to use the system Expat library.
|
|
(Contributed by Arfrever Frehtes Taifersar Arahesis; :issue:`7609`.)
|
|
|
|
* New configure option: the
|
|
:option:`!--with-valgrind` option will now disable the pymalloc
|
|
allocator, which is difficult for the Valgrind memory-error detector
|
|
to analyze correctly.
|
|
Valgrind will therefore be better at detecting memory leaks and
|
|
overruns. (Contributed by James Henstridge; :issue:`2422`.)
|
|
|
|
* New configure option: you can now supply an empty string to
|
|
:option:`!--with-dbmliborder=` in order to disable all of the various
|
|
DBM modules. (Added by Arfrever Frehtes Taifersar Arahesis;
|
|
:issue:`6491`.)
|
|
|
|
* The :program:`configure` script now checks for floating-point rounding bugs
|
|
on certain 32-bit Intel chips and defines a :c:macro:`X87_DOUBLE_ROUNDING`
|
|
preprocessor definition. No code currently uses this definition,
|
|
but it's available if anyone wishes to use it.
|
|
(Added by Mark Dickinson; :issue:`2937`.)
|
|
|
|
:program:`configure` also now sets a :envvar:`LDCXXSHARED` Makefile
|
|
variable for supporting C++ linking. (Contributed by Arfrever
|
|
Frehtes Taifersar Arahesis; :issue:`1222585`.)
|
|
|
|
* The build process now creates the necessary files for pkg-config
|
|
support. (Contributed by Clinton Roy; :issue:`3585`.)
|
|
|
|
* The build process now supports Subversion 1.7. (Contributed by
|
|
Arfrever Frehtes Taifersar Arahesis; :issue:`6094`.)
|
|
|
|
|
|
.. _whatsnew27-capsules:
|
|
|
|
Capsules
|
|
-------------------
|
|
|
|
Python 3.1 adds a new C datatype, :c:type:`PyCapsule`, for providing a
|
|
C API to an extension module. A capsule is essentially the holder of
|
|
a C ``void *`` pointer, and is made available as a module attribute; for
|
|
example, the :mod:`socket` module's API is exposed as ``socket.CAPI``,
|
|
and :mod:`unicodedata` exposes ``ucnhash_CAPI``. Other extensions
|
|
can import the module, access its dictionary to get the capsule
|
|
object, and then get the ``void *`` pointer, which will usually point
|
|
to an array of pointers to the module's various API functions.
|
|
|
|
There is an existing data type already used for this,
|
|
:c:type:`PyCObject`, but it doesn't provide type safety. Evil code
|
|
written in pure Python could cause a segmentation fault by taking a
|
|
:c:type:`PyCObject` from module A and somehow substituting it for the
|
|
:c:type:`PyCObject` in module B. Capsules know their own name,
|
|
and getting the pointer requires providing the name:
|
|
|
|
.. code-block:: c
|
|
|
|
void *vtable;
|
|
|
|
if (!PyCapsule_IsValid(capsule, "mymodule.CAPI") {
|
|
PyErr_SetString(PyExc_ValueError, "argument type invalid");
|
|
return NULL;
|
|
}
|
|
|
|
vtable = PyCapsule_GetPointer(capsule, "mymodule.CAPI");
|
|
|
|
You are assured that ``vtable`` points to whatever you're expecting.
|
|
If a different capsule was passed in, :c:func:`PyCapsule_IsValid` would
|
|
detect the mismatched name and return false. Refer to
|
|
:ref:`using-capsules` for more information on using these objects.
|
|
|
|
Python 2.7 now uses capsules internally to provide various
|
|
extension-module APIs, but the :c:func:`PyCObject_AsVoidPtr` was
|
|
modified to handle capsules, preserving compile-time compatibility
|
|
with the :c:type:`CObject` interface. Use of
|
|
:c:func:`PyCObject_AsVoidPtr` will signal a
|
|
:exc:`PendingDeprecationWarning`, which is silent by default.
|
|
|
|
Implemented in Python 3.1 and backported to 2.7 by Larry Hastings;
|
|
discussed in :issue:`5630`.
|
|
|
|
|
|
.. ======================================================================
|
|
|
|
Port-Specific Changes: Windows
|
|
-----------------------------------
|
|
|
|
* The :mod:`msvcrt` module now contains some constants from
|
|
the :file:`crtassem.h` header file:
|
|
:data:`CRT_ASSEMBLY_VERSION`,
|
|
:data:`VC_ASSEMBLY_PUBLICKEYTOKEN`,
|
|
and :data:`LIBRARIES_ASSEMBLY_NAME_PREFIX`.
|
|
(Contributed by David Cournapeau; :issue:`4365`.)
|
|
|
|
* The :mod:`_winreg` module for accessing the registry now implements
|
|
the :func:`~_winreg.CreateKeyEx` and :func:`~_winreg.DeleteKeyEx`
|
|
functions, extended versions of previously supported functions that
|
|
take several extra arguments. The :func:`~_winreg.DisableReflectionKey`,
|
|
:func:`~_winreg.EnableReflectionKey`, and :func:`~_winreg.QueryReflectionKey`
|
|
were also tested and documented.
|
|
(Implemented by Brian Curtin: :issue:`7347`.)
|
|
|
|
* The new :c:func:`_beginthreadex` API is used to start threads, and
|
|
the native thread-local storage functions are now used.
|
|
(Contributed by Kristján Valur Jónsson; :issue:`3582`.)
|
|
|
|
* The :func:`os.kill` function now works on Windows. The signal value
|
|
can be the constants :const:`CTRL_C_EVENT`,
|
|
:const:`CTRL_BREAK_EVENT`, or any integer. The first two constants
|
|
will send :kbd:`Control-C` and :kbd:`Control-Break` keystroke events to
|
|
subprocesses; any other value will use the :c:func:`TerminateProcess`
|
|
API. (Contributed by Miki Tebeka; :issue:`1220212`.)
|
|
|
|
* The :func:`os.listdir` function now correctly fails
|
|
for an empty path. (Fixed by Hirokazu Yamamoto; :issue:`5913`.)
|
|
|
|
* The :mod:`mimelib` module will now read the MIME database from
|
|
the Windows registry when initializing.
|
|
(Patch by Gabriel Genellina; :issue:`4969`.)
|
|
|
|
.. ======================================================================
|
|
|
|
Port-Specific Changes: Mac OS X
|
|
-----------------------------------
|
|
|
|
* The path ``/Library/Python/2.7/site-packages`` is now appended to
|
|
``sys.path``, in order to share added packages between the system
|
|
installation and a user-installed copy of the same version.
|
|
(Changed by Ronald Oussoren; :issue:`4865`.)
|
|
|
|
.. versionchanged:: 2.7.13
|
|
|
|
As of 2.7.13, this change was removed.
|
|
``/Library/Python/2.7/site-packages``, the site-packages directory
|
|
used by the Apple-supplied system Python 2.7 is no longer appended to
|
|
``sys.path`` for user-installed Pythons such as from the python.org
|
|
installers. As of macOS 10.12, Apple changed how the system
|
|
site-packages directory is configured, which could cause installation
|
|
of pip components, like setuptools, to fail. Packages installed for
|
|
the system Python will no longer be shared with user-installed
|
|
Pythons. (:issue:`28440`)
|
|
|
|
Port-Specific Changes: FreeBSD
|
|
-----------------------------------
|
|
|
|
* FreeBSD 7.1's :const:`SO_SETFIB` constant, used with
|
|
:func:`~socket.getsockopt`/:func:`~socket.setsockopt` to select an
|
|
alternate routing table, is now available in the :mod:`socket`
|
|
module. (Added by Kyle VanderBeek; :issue:`8235`.)
|
|
|
|
Other Changes and Fixes
|
|
=======================
|
|
|
|
* Two benchmark scripts, :file:`iobench` and :file:`ccbench`, were
|
|
added to the :file:`Tools` directory. :file:`iobench` measures the
|
|
speed of the built-in file I/O objects returned by :func:`open`
|
|
while performing various operations, and :file:`ccbench` is a
|
|
concurrency benchmark that tries to measure computing throughput,
|
|
thread switching latency, and IO processing bandwidth when
|
|
performing several tasks using a varying number of threads.
|
|
|
|
* The :file:`Tools/i18n/msgfmt.py` script now understands plural
|
|
forms in :file:`.po` files. (Fixed by Martin von Löwis;
|
|
:issue:`5464`.)
|
|
|
|
* When importing a module from a :file:`.pyc` or :file:`.pyo` file
|
|
with an existing :file:`.py` counterpart, the :attr:`co_filename`
|
|
attributes of the resulting code objects are overwritten when the
|
|
original filename is obsolete. This can happen if the file has been
|
|
renamed, moved, or is accessed through different paths. (Patch by
|
|
Ziga Seilnacht and Jean-Paul Calderone; :issue:`1180193`.)
|
|
|
|
* The :file:`regrtest.py` script now takes a :option:`!--randseed=`
|
|
switch that takes an integer that will be used as the random seed
|
|
for the :option:`!-r` option that executes tests in random order.
|
|
The :option:`!-r` option also reports the seed that was used
|
|
(Added by Collin Winter.)
|
|
|
|
* Another :file:`regrtest.py` switch is :option:`!-j`, which
|
|
takes an integer specifying how many tests run in parallel. This
|
|
allows reducing the total runtime on multi-core machines.
|
|
This option is compatible with several other options, including the
|
|
:option:`!-R` switch which is known to produce long runtimes.
|
|
(Added by Antoine Pitrou, :issue:`6152`.) This can also be used
|
|
with a new :option:`!-F` switch that runs selected tests in a loop
|
|
until they fail. (Added by Antoine Pitrou; :issue:`7312`.)
|
|
|
|
* When executed as a script, the :file:`py_compile.py` module now
|
|
accepts ``'-'`` as an argument, which will read standard input for
|
|
the list of filenames to be compiled. (Contributed by Piotr
|
|
Ożarowski; :issue:`8233`.)
|
|
|
|
.. ======================================================================
|
|
|
|
Porting to Python 2.7
|
|
=====================
|
|
|
|
This section lists previously described changes and other bugfixes
|
|
that may require changes to your code:
|
|
|
|
* The :func:`range` function processes its arguments more
|
|
consistently; it will now call :meth:`__int__` on non-float,
|
|
non-integer arguments that are supplied to it. (Fixed by Alexander
|
|
Belopolsky; :issue:`1533`.)
|
|
|
|
* The string :meth:`format` method changed the default precision used
|
|
for floating-point and complex numbers from 6 decimal
|
|
places to 12, which matches the precision used by :func:`str`.
|
|
(Changed by Eric Smith; :issue:`5920`.)
|
|
|
|
* Because of an optimization for the :keyword:`with` statement, the special
|
|
methods :meth:`__enter__` and :meth:`__exit__` must belong to the object's
|
|
type, and cannot be directly attached to the object's instance. This
|
|
affects new-style classes (derived from :class:`object`) and C extension
|
|
types. (:issue:`6101`.)
|
|
|
|
* Due to a bug in Python 2.6, the *exc_value* parameter to
|
|
:meth:`__exit__` methods was often the string representation of the
|
|
exception, not an instance. This was fixed in 2.7, so *exc_value*
|
|
will be an instance as expected. (Fixed by Florent Xicluna;
|
|
:issue:`7853`.)
|
|
|
|
* When a restricted set of attributes were set using ``__slots__``,
|
|
deleting an unset attribute would not raise :exc:`AttributeError`
|
|
as you would expect. Fixed by Benjamin Peterson; :issue:`7604`.)
|
|
|
|
In the standard library:
|
|
|
|
* Operations with :class:`~datetime.datetime` instances that resulted in a year
|
|
falling outside the supported range didn't always raise
|
|
:exc:`OverflowError`. Such errors are now checked more carefully
|
|
and will now raise the exception. (Reported by Mark Leander, patch
|
|
by Anand B. Pillai and Alexander Belopolsky; :issue:`7150`.)
|
|
|
|
* When using :class:`~decimal.Decimal` instances with a string's
|
|
:meth:`format` method, the default alignment was previously
|
|
left-alignment. This has been changed to right-alignment, which might
|
|
change the output of your programs.
|
|
(Changed by Mark Dickinson; :issue:`6857`.)
|
|
|
|
Comparisons involving a signaling NaN value (or ``sNAN``) now signal
|
|
:const:`~decimal.InvalidOperation` instead of silently returning a true or
|
|
false value depending on the comparison operator. Quiet NaN values
|
|
(or ``NaN``) are now hashable. (Fixed by Mark Dickinson;
|
|
:issue:`7279`.)
|
|
|
|
* The ElementTree library, :mod:`xml.etree`, no longer escapes
|
|
ampersands and angle brackets when outputting an XML processing
|
|
instruction (which looks like ``<?xml-stylesheet href="#style1"?>``)
|
|
or comment (which looks like ``<!-- comment -->``).
|
|
(Patch by Neil Muller; :issue:`2746`.)
|
|
|
|
* The :meth:`~StringIO.StringIO.readline` method of :class:`~StringIO.StringIO` objects now does
|
|
nothing when a negative length is requested, as other file-like
|
|
objects do. (:issue:`7348`).
|
|
|
|
* The :mod:`syslog` module will now use the value of ``sys.argv[0]`` as the
|
|
identifier instead of the previous default value of ``'python'``.
|
|
(Changed by Sean Reifschneider; :issue:`8451`.)
|
|
|
|
* The :mod:`tarfile` module's default error handling has changed, to
|
|
no longer suppress fatal errors. The default error level was previously 0,
|
|
which meant that errors would only result in a message being written to the
|
|
debug log, but because the debug log is not activated by default,
|
|
these errors go unnoticed. The default error level is now 1,
|
|
which raises an exception if there's an error.
|
|
(Changed by Lars Gustäbel; :issue:`7357`.)
|
|
|
|
* The :mod:`urlparse` module's :func:`~urlparse.urlsplit` now handles
|
|
unknown URL schemes in a fashion compliant with :rfc:`3986`: if the
|
|
URL is of the form ``"<something>://..."``, the text before the
|
|
``://`` is treated as the scheme, even if it's a made-up scheme that
|
|
the module doesn't know about. This change may break code that
|
|
worked around the old behaviour. For example, Python 2.6.4 or 2.5
|
|
will return the following:
|
|
|
|
.. doctest::
|
|
:options: +SKIP
|
|
|
|
>>> import urlparse
|
|
>>> urlparse.urlsplit('invented://host/filename?query')
|
|
('invented', '', '//host/filename?query', '', '')
|
|
|
|
Python 2.7 (and Python 2.6.5) will return:
|
|
|
|
.. doctest::
|
|
:options: +SKIP
|
|
|
|
>>> import urlparse
|
|
>>> urlparse.urlsplit('invented://host/filename?query')
|
|
('invented', 'host', '/filename?query', '', '')
|
|
|
|
(Python 2.7 actually produces slightly different output, since it
|
|
returns a named tuple instead of a standard tuple.)
|
|
|
|
For C extensions:
|
|
|
|
* C extensions that use integer format codes with the ``PyArg_Parse*``
|
|
family of functions will now raise a :exc:`TypeError` exception
|
|
instead of triggering a :exc:`DeprecationWarning` (:issue:`5080`).
|
|
|
|
* Use the new :c:func:`PyOS_string_to_double` function instead of the old
|
|
:c:func:`PyOS_ascii_strtod` and :c:func:`PyOS_ascii_atof` functions,
|
|
which are now deprecated.
|
|
|
|
For applications that embed Python:
|
|
|
|
* The :c:func:`PySys_SetArgvEx` function was added, letting
|
|
applications close a security hole when the existing
|
|
:c:func:`PySys_SetArgv` function was used. Check whether you're
|
|
calling :c:func:`PySys_SetArgv` and carefully consider whether the
|
|
application should be using :c:func:`PySys_SetArgvEx` with
|
|
*updatepath* set to false.
|
|
|
|
.. ======================================================================
|
|
|
|
|
|
.. _py27-maintenance-enhancements:
|
|
|
|
New Features Added to Python 2.7 Maintenance Releases
|
|
=====================================================
|
|
|
|
New features may be added to Python 2.7 maintenance releases when the
|
|
situation genuinely calls for it. Any such additions must go through
|
|
the Python Enhancement Proposal process, and make a compelling case for why
|
|
they can't be adequately addressed by either adding the new feature solely to
|
|
Python 3, or else by publishing it on the Python Package Index.
|
|
|
|
In addition to the specific proposals listed below, there is a general
|
|
exemption allowing new ``-3`` warnings to be added in any Python 2.7
|
|
maintenance release.
|
|
|
|
|
|
Two new environment variables for debug mode
|
|
--------------------------------------------
|
|
|
|
In debug mode, the ``[xxx refs]`` statistic is not written by default, the
|
|
:envvar:`PYTHONSHOWREFCOUNT` environment variable now must also be set.
|
|
(Contributed by Victor Stinner; :issue:`31733`.)
|
|
|
|
When Python is compiled with ``COUNT_ALLOC`` defined, allocation counts are no
|
|
longer dumped by default anymore: the :envvar:`PYTHONSHOWALLOCCOUNT` environment
|
|
variable must now also be set. Moreover, allocation counts are now dumped into
|
|
stderr, rather than stdout. (Contributed by Victor Stinner; :issue:`31692`.)
|
|
|
|
.. versionadded:: 2.7.15
|
|
|
|
|
|
PEP 434: IDLE Enhancement Exception for All Branches
|
|
----------------------------------------------------
|
|
|
|
:pep:`434` describes a general exemption for changes made to the IDLE
|
|
development environment shipped along with Python. This exemption makes it
|
|
possible for the IDLE developers to provide a more consistent user
|
|
experience across all supported versions of Python 2 and 3.
|
|
|
|
For details of any IDLE changes, refer to the NEWS file for the specific
|
|
release.
|
|
|
|
|
|
PEP 466: Network Security Enhancements for Python 2.7
|
|
-----------------------------------------------------
|
|
|
|
:pep:`466` describes a number of network security enhancement proposals
|
|
that have been approved for inclusion in Python 2.7 maintenance releases,
|
|
with the first of those changes appearing in the Python 2.7.7 release.
|
|
|
|
:pep:`466` related features added in Python 2.7.7:
|
|
|
|
* :func:`hmac.compare_digest` was backported from Python 3 to make a timing
|
|
attack resistant comparison operation available to Python 2 applications.
|
|
(Contributed by Alex Gaynor; :issue:`21306`.)
|
|
|
|
* OpenSSL 1.0.1g was upgraded in the official Windows installers published on
|
|
python.org. (Contributed by Zachary Ware; :issue:`21462`.)
|
|
|
|
:pep:`466` related features added in Python 2.7.8:
|
|
|
|
* :func:`hashlib.pbkdf2_hmac` was backported from Python 3 to make a hashing
|
|
algorithm suitable for secure password storage broadly available to Python
|
|
2 applications. (Contributed by Alex Gaynor; :issue:`21304`.)
|
|
|
|
* OpenSSL 1.0.1h was upgraded for the official Windows installers published on
|
|
python.org. (contributed by Zachary Ware in :issue:`21671` for CVE-2014-0224)
|
|
|
|
:pep:`466` related features added in Python 2.7.9:
|
|
|
|
* Most of Python 3.4's :mod:`ssl` module was backported. This means :mod:`ssl`
|
|
now supports Server Name Indication, TLS1.x settings, access to the platform
|
|
certificate store, the :class:`~ssl.SSLContext` class, and other
|
|
features. (Contributed by Alex Gaynor and David Reid; :issue:`21308`.)
|
|
|
|
Refer to the "Version added: 2.7.9" notes in the module documentation for
|
|
specific details.
|
|
|
|
* :func:`os.urandom` was changed to cache a file descriptor to ``/dev/urandom``
|
|
instead of reopening ``/dev/urandom`` on every call. (Contributed by Alex
|
|
Gaynor; :issue:`21305`.)
|
|
|
|
* :data:`hashlib.algorithms_guaranteed` and
|
|
:data:`hashlib.algorithms_available` were backported from Python 3 to make
|
|
it easier for Python 2 applications to select the strongest available hash
|
|
algorithm. (Contributed by Alex Gaynor in :issue:`21307`)
|
|
|
|
|
|
PEP 477: Backport ensurepip (PEP 453) to Python 2.7
|
|
---------------------------------------------------
|
|
|
|
:pep:`477` approves the inclusion of the :pep:`453` ensurepip module and the
|
|
improved documentation that was enabled by it in the Python 2.7 maintenance
|
|
releases, appearing first in the Python 2.7.9 release.
|
|
|
|
|
|
Bootstrapping pip By Default
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
The new :mod:`ensurepip` module (defined in :pep:`453`) provides a standard
|
|
cross-platform mechanism to bootstrap the pip installer into Python
|
|
installations. The version of ``pip`` included with Python 2.7.9 is ``pip``
|
|
1.5.6, and future 2.7.x maintenance releases will update the bundled version to
|
|
the latest version of ``pip`` that is available at the time of creating the
|
|
release candidate.
|
|
|
|
By default, the commands ``pip``, ``pipX`` and ``pipX.Y`` will be installed on
|
|
all platforms (where X.Y stands for the version of the Python installation),
|
|
along with the ``pip`` Python package and its dependencies.
|
|
|
|
For CPython :ref:`source builds on POSIX systems <building-python-on-unix>`,
|
|
the ``make install`` and ``make altinstall`` commands do not bootstrap ``pip``
|
|
by default. This behaviour can be controlled through configure options, and
|
|
overridden through Makefile options.
|
|
|
|
On Windows and Mac OS X, the CPython installers now default to installing
|
|
``pip`` along with CPython itself (users may opt out of installing it
|
|
during the installation process). Window users will need to opt in to the
|
|
automatic ``PATH`` modifications to have ``pip`` available from the command
|
|
line by default, otherwise it can still be accessed through the Python
|
|
launcher for Windows as ``py -m pip``.
|
|
|
|
As `discussed in the PEP`__, platform packagers may choose not to install
|
|
these commands by default, as long as, when invoked, they provide clear and
|
|
simple directions on how to install them on that platform (usually using
|
|
the system package manager).
|
|
|
|
__ https://peps.python.org/pep-0477/#disabling-ensurepip-by-downstream-distributors
|
|
|
|
|
|
Documentation Changes
|
|
~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
As part of this change, the :ref:`installing-index` and
|
|
:ref:`distributing-index` sections of the documentation have been
|
|
completely redesigned as short getting started and FAQ documents. Most
|
|
packaging documentation has now been moved out to the Python Packaging
|
|
Authority maintained `Python Packaging User Guide
|
|
<https://packaging.python.org>`__ and the documentation of the individual
|
|
projects.
|
|
|
|
However, as this migration is currently still incomplete, the legacy
|
|
versions of those guides remaining available as :ref:`install-index`
|
|
and :ref:`setuptools-index`.
|
|
|
|
.. seealso::
|
|
|
|
:pep:`453` -- Explicit bootstrapping of pip in Python installations
|
|
PEP written by Donald Stufft and Nick Coghlan, implemented by
|
|
Donald Stufft, Nick Coghlan, Martin von Löwis and Ned Deily.
|
|
|
|
PEP 476: Enabling certificate verification by default for stdlib http clients
|
|
-----------------------------------------------------------------------------
|
|
|
|
:pep:`476` updated :mod:`httplib` and modules which use it, such as
|
|
:mod:`urllib2` and :mod:`xmlrpclib`, to now verify that the server
|
|
presents a certificate which is signed by a Certificate Authority in the
|
|
platform trust store and whose hostname matches the hostname being requested
|
|
by default, significantly improving security for many applications. This
|
|
change was made in the Python 2.7.9 release.
|
|
|
|
For applications which require the old previous behavior, they can pass an
|
|
alternate context::
|
|
|
|
import urllib2
|
|
import ssl
|
|
|
|
# This disables all verification
|
|
context = ssl._create_unverified_context()
|
|
|
|
# This allows using a specific certificate for the host, which doesn't need
|
|
# to be in the trust store
|
|
context = ssl.create_default_context(cafile="/path/to/file.crt")
|
|
|
|
urllib2.urlopen("https://invalid-cert", context=context)
|
|
|
|
|
|
PEP 493: HTTPS verification migration tools for Python 2.7
|
|
----------------------------------------------------------
|
|
|
|
:pep:`493` provides additional migration tools to support a more incremental
|
|
infrastructure upgrade process for environments containing applications and
|
|
services relying on the historically permissive processing of server
|
|
certificates when establishing client HTTPS connections. These additions were
|
|
made in the Python 2.7.12 release.
|
|
|
|
These tools are intended for use in cases where affected applications and
|
|
services can't be modified to explicitly pass a more permissive SSL context
|
|
when establishing the connection.
|
|
|
|
For applications and services which can't be modified at all, the new
|
|
``PYTHONHTTPSVERIFY`` environment variable may be set to ``0`` to revert an
|
|
entire Python process back to the default permissive behaviour of Python 2.7.8
|
|
and earlier.
|
|
|
|
For cases where the connection establishment code can't be modified, but the
|
|
overall application can be, the new :func:`ssl._https_verify_certificates`
|
|
function can be used to adjust the default behaviour at runtime.
|
|
|
|
|
|
New ``make regen-all`` build target
|
|
-----------------------------------
|
|
|
|
To simplify cross-compilation, and to ensure that CPython can reliably be
|
|
compiled without requiring an existing version of Python to already be
|
|
available, the autotools-based build system no longer attempts to implicitly
|
|
recompile generated files based on file modification times.
|
|
|
|
Instead, a new ``make regen-all`` command has been added to force regeneration
|
|
of these files when desired (e.g. after an initial version of Python has
|
|
already been built based on the pregenerated versions).
|
|
|
|
More selective regeneration targets are also defined - see
|
|
:source:`Makefile.pre.in` for details.
|
|
|
|
(Contributed by Victor Stinner in :issue:`23404`.)
|
|
|
|
.. versionadded:: 2.7.14
|
|
|
|
|
|
Removal of ``make touch`` build target
|
|
--------------------------------------
|
|
|
|
The ``make touch`` build target previously used to request implicit regeneration
|
|
of generated files by updating their modification times has been removed.
|
|
|
|
It has been replaced by the new ``make regen-all`` target.
|
|
|
|
(Contributed by Victor Stinner in :issue:`23404`.)
|
|
|
|
.. versionchanged:: 2.7.14
|
|
|
|
.. ======================================================================
|
|
|
|
.. _acks27:
|
|
|
|
Acknowledgements
|
|
================
|
|
|
|
The author would like to thank the following people for offering
|
|
suggestions, corrections and assistance with various drafts of this
|
|
article: Nick Coghlan, Philip Jenvey, Ryan Lovett, R. David Murray,
|
|
Hugh Secker-Walker.
|