Try to inplace upgrade from python 2.5 to 2.7

inplace-upgrade.py

#!/usr/bin/env python2
'''
    # ./inplace-upgrade.py
    python version:  (2, 5, 2, 'final', 0)
    [***] newer python interpreter available. switching versions... 
    python version:  sys.version_info(major=2, minor=7, micro=9, releaselevel='final', serial=0)
'''
import os, sys

def try_switch_to_python2_7():
    py27 = "/usr/bin/python2.7"
    if sys.version_info < (2,7) and os.path.exists(py27):
        print  "[***] newer python interpreter available. switching versions... "
        os.execve(py27,[py27]+sys.argv,os.environ)
        sys.exit()

print "python version: ", sys.version_info
try_switch_to_python2_7()