14

I have the following project structure:

project/
    example/
        __init__.py
        foo.py
        boo.py
        meh.py
    tests/
        example/
            test_foo.py
            test_boo.py
            test_meh.py

As example, I'm importing foo.py in boo.py as import example.foo as f. And I'm running tests with python3 -m pytest -s -v --cov tests on root folder (project). The unit tests are running very smooth but when I try to run a single file as python3 example/boo.py I got an error:

ModuleNotFoundError: No module named 'example'
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12
  • What is the right approach? Commented Mar 11, 2019 at 13:25
  • 1
    The right approach is not to run modules directly. Commented Mar 11, 2019 at 13:26
  • Note that pytest will also not run the modules, since there is no test prepended. Perhaps if you pass the --docttest-modules option, but then it will run the doctests, not the actual modules. Commented Mar 11, 2019 at 13:27
  • 2
    Put scripts in a separate directory next to your package, e.g. project/example/ and project/scripts/. Commented Mar 11, 2019 at 13:41
  • 2
    It may be worth reading up on Python packaging, though admittedly, there is a lot to read and learn. It definitely extends outside the scope of your question, but it would hopefully answer questions such as about where scripts should go. Commented Mar 11, 2019 at 13:43

3 Answers 3

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16

Modules inside a package shouldn't really be run (some exceptions).

But, you can set a PYTHONPATH before running the module if you really want. For a one off, use e.g.

PYTHONPATH=$(pwd) python3 example/boo.py

An alternative is to use relative imports: from . import foo as f inside boo.py. But that still implies that modules shouldn't really be run.

To elaborate a bit more: A module should be imported, not run like a script. That is what a module is for. If, for some reason, you really really feel you need to execute module, then 1/ reconsider, 2/ rewrite your module, 3/ wrap a script around that module by calling the necessary function(s) inside the module (and keep the script itself relatively short).

Note that setuptools already has this functionality through entry points.

A simpler alternative is to use a proper

if __name__ == '__main__':
    main()

line at the end of your module, where main() calls into your module functionality, then execute the module using the Python -m switch:

python -m mypackage.mymodule

But, again, try and limit this functionality.

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7

It's usually a problem with environment variables. You can force the path using the following, and the import should work under all circumstances:

import sys
sys.path.append("/absolute/module/path")
import local_module
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1 Comment

Don't do this. You hacked an (absolute) path into the Python program. Now you give this program to a colleague who's running this on another machine, and it will fail, because that path doesn't exist.
-1

I was also facing the same error, first try to import the same module in interactive shell of python with python

import module

if this imports successfully, try checking the paths using sys in the interactive shell

print(sys.path)

This will print a list of paths which are considered, Now do the same in your python file add the below lines above all imports.

import sys
print(sys.path)

this will also print a list of paths. Now compare the two paths one received from the interactive python shell and one from the output of the python file. Add the path that is missing with

sys.path.append("missing_path")

for me

sys.path.append("")

worked as I was wanted to import module from the current folder

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