The “officially” supported versions of Python are the versions that ship with Softimage.
Python 2.6.4 & PyWin 212
We didn’t go with 2.7 because of a bug in PyWin 214.
You can use Python 2.7 if you have it installed on your system: just disable the internal Python in the scripting preferences.
Softimage won’t work with Python 3.x
Softimage ships with Python 2.5 because we needed to compile [and distribute] the pywin32 module for a specific Python version on Linux.