スクリプトを実行しているPythonのバージョンを確認するにはどうすればいいですか？

>>> import sys

>>> print(sys.version)  # parentheses necessary in python 3.       
2.5.2 (r252:60911, Jul 31 2008, 17:28:52) 
[GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)]

>>> sys.version_info
(2, 5, 2, 'final', 0)
# or
>>> sys.hexversion
34014192

assert sys.version_info >= (2, 5)

>>> import sys
>>> sys.version_info
(2, 6, 4, 'final', 0)
>>> if not sys.version_info[:2] == (2, 6):
...    print "Error, I need python 2.6"
... else:
...    from my_module import twoPointSixCode
>>> 

>>> try:
...     from my_module import twoPointSixCode
... except Exception: 
...     print "can't import, probably because your python is too old!"
>>>

import sys
sys.version.split(' ')[0]