python2.7.4最新发布，修正上百bug

Python 今天发布了Python 2.7.4，该版本修正了上百个bugs。

python2.7.x是python2.x系列的最后一个重要版本，它包含了python3.1中的很多重要特性

本次更新的重要特性：

An ordered dictionary type

New unittest features including test skipping, new assert methods, and test discovery

A much faster io module

Automatic numbering of fields in the str.format() method

Float repr improvements backported from 3.x

Tile support for Tkinter

A backport of the memoryview object from 3.x

Set literals

Set and dictionary comprehensions

Dictionary views

New syntax for nested with statements

The sysconfig module