ModuleNotFoundError: 没有名为“src”的模块。 从没有 sys.path 的另一个目录导入模块并从现有目录执行它们

Question

Even though it is a common question, I believe I have a weird situation

MAIN
| --src
     | -- data 
            | -- __init__.py
            | -- operation.py
| tests
          | __init__.py
          | test_file.py
| examples
          | __init__.py
          | example.py

The contents of test_file.py and example.py are as follows:

from src.data.operation import *

I execute the following command from the powershell by navigating inside the tests folder:

python -m pytest -v test_file.py

The test file runs fine without giving any errors.

Now I execute the following command from the powershell by navigating inside the examples folder:

python -m example.py

This throws me the module error. Even though tests and examples are in the same hierarchy as src, I get the module error only when I execute the example.py file by navigating inside the examples folder. It would be great if someone could explain the logic behind this and what would be the best way to execute example.py in a windows system that does not involve sys.path?

Answer 1

It is not possible to import without appending sys.path. By default, Python looks for its modules and packages in $PYTHONPATH. When you import something in the module it 1st searches for a built-in module with that name, it then searches for a file or folder in the list of directories given by the variable sys.path.

To successfully import from src, add these lines on top of the example.py

import sys
sys.path.insert(0, "PATH_TO_THE_MAIN_FOLDER")

run the module from inside examples folder:

python -m example