When the codes in python file run when it's being imported?

Question

I have two files, say main.py and foo.py. When I import foo in main, I thought the lines in foo.py that not in a function automaticly run.

But when I add an executable to PATH in foo, and call main of foo that involves that executable which should be in PATH, it gives an error: geckodriver executable must be in PATH. If I add it to PATH right after the imports in main.py, it works correctly. Here are the sample codes:

main.py:

# some imports
from foo_file import foo

foo.main()

foo.py:

import os

FILENAME = os.path.dirname(os.path.abspath(__file__))

os.environ["PATH"] += os.pathsep + os.path.join(FILENAME, "assets")

def main():
    # some work involves selenium

Why the first try doesn't work and gives the error? Thanks.

tobias_k · Accepted Answer · 2019-11-25 15:19:12Z

2

This is kind of a wild guess, but since you are importing foo as

from foo_file import foo

I assume that foo is in a sub-directory, i.e. something like

+- main.py
\- foo_file
   \- foo.py

Thus, when you add os.path.abspath(__file__) to PATH, it will add the path of the subdirectory, not of the directory containing the main.py, which is probably the directory that contains the assets folder, since you said that it works fine if the PATH-adding code is directly in main.

You can easily check (a) that and when the code is executed, and (b) which path is retrieved, if you add an accordant print line in both the foo.py and main.py files, e.g.

print(__file__, os.path.dirname(os.path.abspath(__file__)))

answered Nov 25, 2019 at 15:19

tobias_k

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2 Comments

emremrah Over a year ago

Aw yess, you absolutely correct, how I didn't see that. Thanks, I will try it asap.

emremrah Over a year ago

Do you know how can I get the path of assets from foo in a good way?

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