if in2 and not in3:
    return '2'
if in3 and not in2:
    return '3'
return default
no = analyse(args[1], default='2')
if args[1][-1:] == 'w':
    cmd = 'C:\x08in\\pythonw%s.bat'
else:
    cmd = 'C:\x08in\\python%s.bat'
i = os.system(cmd % no + ' ' + ' '.join(args[1:]))
if type(i) != int:
    i = 0
exit(i)
How to use multiple versions of Python without uninstallation