Python: What OS am I running on?

>>> import os
>>> os.name
'posix'
>>> import platform
>>> platform.system()
'Linux'
>>> platform.release()
'2.6.22-15-generic'

The output of platform.system() is as follows:

• Linux: Linux
• Mac: Darwin
• Windows: Windows

See: platform — Access to underlying platform’s identifying data

Dang -- lbrandy beat me to the punch, but that doesn't mean I can't provide you with the system results for Vista!

>>> import os
>>> os.name
'nt'
>>> import platform
>>> platform.system()
'Windows'
>>> platform.release()
'Vista'

...and I can’t believe no one’s posted one for Windows 10 yet:

>>> import os
>>> os.name
'nt'
>>> import platform
>>> platform.system()
'Windows'
>>> platform.release()
'10'

For the record here's the results on Mac:

>>> import os
>>> os.name
'posix'
>>> import platform
>>> platform.system()
'Darwin'
>>> platform.release()
'8.11.1'

Sample code to differentiate OS's using python:

from sys import platform as _platform

if _platform == "linux" or _platform == "linux2":
    # linux
elif _platform == "darwin":
    # MAC OS X
elif _platform == "win32":
    # Windows
elif _platform == "win64":
    # Windows 64-bit