Python 发布 3.4.0 的第二个 Alpha 版本，下载地址：
http://www.python.org/ftp/python/3.4.0/Python-3.4.0a2.tar.bz2
与 3.3 版本比较，3.4 主要的改进有：
PEP 435, a standardized "enum" module
PEP 442, improved semantics for object finalization
PEP 443, adding single-dispatch generic functions to the standard library
PEP 445, a new C API for implementing custom memory allocators
PEP 446, changing file descriptors to not be inherited by default in subprocesses
来自:开源中国社区
