Python: Platform independent way to modify PATH environment variable

You should be able to modify os.environ.

Since os.pathsep is the character to separate different paths, you should use this to append each new path:

os.environ["PATH"] += os.pathsep + path

or, if there are several paths to add in a list:

os.environ["PATH"] += os.pathsep + os.pathsep.join(pathlist)

As you mentioned, os.path.join can also be used for each individual path you have to append in the case you have to construct them from separate parts.

Please note that os.environ is not actually a dictionary. It's a special dictionary-like object which actually sets environment variables in the current process using setenv.

>>> os.environ.__class__
<class os._Environ at 0x100472050>
>>> import os
>>> os.environ["HELLO"] = "WORLD"
>>> os.getenv("HELLO")
'WORLD'

This means that PATH (and other environment variables) will be visible to C code run in the same process.

(Since comments can't contain formatting, I have to put this in an answer, but I feel like it's an important point to make. This is really a comment on the comment about there being no equivalent to 'export'.)