Python subprocess can't find Pythonpath module

Question

I am trying to use subprocess.run(['python3.9', "scripts/example.py"], check=True).

example.py uses a module, that I have added to the PYTHONPATH. However, whenever I run the above line, the module is not found.

The confusing part for me is, that printing sys.path inside of example.py I do see the path to my module. But when I am running os.system("which python") or os.system("echo $PYTHONPATH") inside example.py, it returns/prints nothing.

Are you using a virtual environment? -- Typically, you would want to use the exact same Python interpreter for the sub-process call, so you would write: subprocess.run([sys.executable, 'scripts/example.py', check=True), unless of course you really do want python3.9 explicitly and nothing else (which would be surprising). -- And finally, you should check the doc for the env parameter of subprocess.run. — sinoroc
– sinoroc, Commented Nov 22, 2022 at 12:57
Thank you! using sys.executable and setting the env parameter to a copy of my environment variables where I manually added the pythonpath I needed solved the issue for me. Thank you so much! This bug took me my whole day to fix :D — mayool
– mayool, Commented Nov 22, 2022 at 14:57
Running Python as a subprocess of Python is often dubious. The simple and elegant solution is to import the code you want to run, and not run it in a subprocess at all. — tripleee
– tripleee, Commented Nov 22, 2022 at 15:42

sinoroc · Accepted Answer · 2022-11-22 16:58:17Z

2

Looks like you need to check the doc for the env parameter of subprocess.run and set it appropriately.

Side note: typically you would want to use the exact same Python interpreter for the sub-process call, so you would write: subprocess.run([sys.executable, 'scripts/example.py'], ...), unless of course you really do want 'python3.9' explicitly and nothing else (which would be surprising).

edited Nov 22, 2022 at 16:58

answered Nov 22, 2022 at 15:24

sinoroc

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