How path should be configured for a python project?

问题

After exhaustive research on this topic the past few days, I still don't understand what is the proper way to handle python path for a specific project. I describe below the situation that I am in and the exact question I have about it.

Problem statement

I have downloaded a project that I want to work on from GitHub. An abstract structure of the project is represented below, having removed unnecessary components:

project
|-- experiments
|   |-- cnn_experiments
|       |-- __init__.py
|       |-- train.py
|       |-- datasets
|           |-- __init__.py
|           |-- module_A.py
|-- src
    |-- cnn
        |-- io
            |-- __init__.py
            |-- module_B.py

Note: from the structure above are missing only some directories under cnn directory with some extra functionalities. Except for this, the structure is the same as I downloaded it from GitHub.

In train.py there is the following import statement:

from cnn_experiments.datasets.module_A import Class_A

From inside cnn_experiments directory I run python train.py command and I get this error:

ImportError: No module named cnn_experiments.datasets.module_A

Similarly, I get the corresponding error when I run module_A.py that has the import statement:

from cnn.io.module_B import Class_B

Especially for the second case, that the path is completely different, when I use print(sys.path) from inside train.py I can tell that Python can't resolve where my import refers to, but the problem is why.

Question

In this case, that the project is small, how can I have full access to import all the directories? I came across with some answers which refer to changing PYTHONPATH in .bashrc file. But it doesn't make sense to me configuring .bashrc exporting to it the path for every project.
Since I understand that having full access from every module to every other module in a project is not generally desired for the sake of abstractness and independence, how can I set up the path so that the modules to be imported are visible?

Thanks in advance for any help!

EDIT: I forgot to mention that I use Python 2.7 on Ubuntu 18.04 LTS.

来源：https://stackoverflow.com/questions/65014153/how-path-should-be-configured-for-a-python-project

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