Interface for modifying Windows environment variables from Python

Question

How can I persistently modify the Windows environment variables from a Python script? (it\'s the setup.py script)

I\'m looking for a standard function or module to u

Answer 1

It may be just as easy to use the external Windows setx command:

C:\>set NEWVAR
Environment variable NEWVAR not defined

C:\>python
Python 2.5.4 (r254:67916, Dec 23 2008, 15:10:54) [MSC v.1310 32 bit (Intel)] on
win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.system('setx NEWVAR newvalue')
0
>>> os.getenv('NEWVAR')
>>> ^Z


C:\>set NEWVAR
Environment variable NEWVAR not defined

Now open a new Command Prompt:

C:\>set NEWVAR
NEWVAR=newvalue

As you can see, setx neither sets the variable for the current session, nor for the parent process (the first Command Prompt). But it does set the variable persistently in the registry for future processes.

I don't think there is a way of changing the parent process's environment at all (and if there is, I'd love to hear it!).