Author A.M. Kuchling (amk at amk.ca)
This article explains the new features in Python 2.7. Python 2.7 was released on July 3, 2010.
Numeric handling has been improved in many ways, for both floating-point numbers and for the Decimal class.
There are some useful additions to the standard library, such as a greatly enhanced unittest module, the
argparse module for parsing command-line options, convenient OrderedDict and Counter classes in the
collections module, and many other improvements.
Python 2.7 is planned to be the last of the 2.x releases, so we worked on making it a good release for the long
term. To help with porting to Python 3, several new features from the Python 3.x series have been included in 2.7.
This article doesn’t attempt to provide a complete specification of the new features, but instead provides a conve-
nient overview. For full details, you should refer to the documentation for Python 2.7 at http://docs.python.org.
If you want to understand the rationale for the design and implementation, refer to the PEP for a particular new
feature or the issue on http://bugs.python.org in which a change was discussed. Whenever possible, “What’s New
in Python” links to the bug/patch item for each change.
1 The Future for Python 2.x
Python 2.7 is intended to be the last major release in the 2.x series. The Python maintainers are planning to focus
their future efforts on the Python 3.x series.
This means that 2.7 will remain in place for a long time, running production systems that have not been ported to
Python 3.x. Two consequences of the long-term significance of 2.7 are:
• It’s very likely the 2.7 release will have a longer period of maintenance compared to earlier 2.x versions.
Python 2.7 will continue to be maintained while the transition to 3.x continues, and the developers are
planning to support Python 2.7 with bug-fix releases beyond the typical two years.
• A policy decision was made to silence warnings only of interest to developers. DeprecationWarning
and its descendants are now ignored unless otherwise requested, preventing users from seeing warnings trig-
gered by an application. This change was also made in the branch that will become Python 3.2. (Discussed
on stdlib-sig and carried out in issue 7319.)
In previous releases, DeprecationWarning messages were enabled by default, providing Python de-
velopers with a clear indication of where their code may break in a future major version of Python.
However, there are increasingly many users of Python-based applications who are not directly involved in
the development of those applications. DeprecationWarning messages are irrelevant to such users,
making them worry about an application that’s actually working correctly and burdening application devel-
opers with responding to these concerns.
You can re-enable display of DeprecationWarning messages by running Python with the
-Wdefault (short form: -Wd) switch, or by setting the PYTHONWARNINGS environment variable
to "default" (or "d") before running Python. Python code can also re-enable them by calling
warnings.simplefilter(’default’).
2 Python 3.1 Features
Much as Python 2.6 incorporated features from Python 3.0, version 2.7 incorporates some of the new features in
Python 3.1. The 2.x series continues to provide tools for migrating to the 3.x series.
A partial list of 3.1 features that were backported to 2.7:
• The syntax for set literals ({1,2,3} is a mutable set).
• Dictionary and set comprehensions ({i: i
*
2 for i in range(3)}).
• Multiple context managers in a single with statement.
• A new version of the io library, rewritten in C for performance.
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liandesinian2015-03-19很好的资源，很详细。
