Can you get original, system's PATH variable value in python?

Question

So, when I import a certain module in my python script, a new path gets added to os.environ['PATH']. Also I launch my script in conda enviroment, which also adds a bunch of new entries to PATH. Is there an any way I can get original value of PATH (original in a sense that what I would get if I call echo $PATH or echo %PATH% in system's terminal)?

The reason I need this is because I need to call a specific binary in my script with subprocess.run. The binary I'm executing and the library I'm importing in my script are related in a sense that they are based on the same project, which causes my binary to fail when PATH contains entry to module's dll files. If I don't import this module a call to subprocess.run works fine, but if I do it fails without any error.

Of course If I know what path I need to remove from the PATH it is easy to modify os.environ['PATH']:

path_to_remove = r"C:\ProgramData\Anaconda3\envs\ppp\lib\site-packages\mip\libraries\win64"
saved_path = os.environ['PATH'] 
path_list = os.environ['PATH'].split(os.pathsep)
path_list.remove(path_to_remove)
os.environ['PATH'] = os.pathsep.join(path_list)
# a call to subprocess.run
os.environ['PATH'] = saved_path 
# Or you can copy os.environ, modify it and pass it as env argument to subprocess.run

But I'm looking for more stable, preferably cross-platform way of doing it.

blhsing · Accepted Answer · 2022-07-15 09:43:26Z

1

You can save the original value of the environment variable in a separate variable before you import the said module, so that you can restore the value of the environment variable from that variable before calling subprocess.run. Use unittest.mock.patch.dict as a context manager around the call to make the modification to PATH temporary:

from unittest.mock import patch
import os
original_path = os.environ['PATH'] # save the original path before importing mip

...

import mip

...

with patch.dict('os.environ', {'PATH': original_path}):
    subprocess.run(...)

edited Jul 15, 2022 at 9:43

answered Jul 15, 2022 at 8:50

blhsing

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