Sibling package imports

Question

I've tried reading through questions about sibling imports and even the package documentation, but I've yet to find an answer.

With the following structure:

├── LICENSE.md
├── README.md
├── api
│   ├── __init__.py
│   ├── api.py
│   └── api_key.py
├── examples
│   ├── __init__.py
│   ├── example_one.py
│   └── example_two.py
└── tests
│   ├── __init__.py
│   └── test_one.py

How can the scripts in the examples and tests directories import from the api module and be run from the commandline?

Also, I'd like to avoid the ugly sys.path.insert hack for every file. Surely this can be done in Python, right?

Answer 1

TLDR

This method does not require setuptools, path hacks, additional command line arguments, or specifying the top level of the package in every single file of your project.

Just make a script in the parent directory of whatever your are calling to be your __main__ and run everything from there. For further explanation continue reading.

Explanation

This can be accomplished without hacking a new path together, extra command line args, or adding code to each of your programs to recognize its siblings.

The reason this fails as I believe was mentioned before is the programs being called have their __name__ set as __main__. When this occurs the script being called accepts itself to be on the top level of the package and refuses to recognize scripts in sibling directories.

However, everything under the top level of the directory will still recognize ANYTHING ELSE under the top level. This means the ONLY thing you have to do to get files in sibling directories to recognize/utilize each other is to call them from a script in their parent directory.

Proof of Concept In a dir with the following structure:

.
|__Main.py
|
|__Siblings
   |
   |___sib1
   |   |
   |   |__call.py
   |
   |___sib2
       |
       |__callsib.py

Main.py contains the following code:

import sib1.call as call


def main():
    call.Call()


if __name__ == '__main__':
    main()

sib1/call.py contains:

import sib2.callsib as callsib


def Call():
    callsib.CallSib()


if __name__ == '__main__':
    Call()

and sib2/callsib.py contains:

def CallSib():
    print("Got Called")

if __name__ == '__main__':
    CallSib()

If you reproduce this example you will notice that calling Main.py will result in "Got Called" being printed as is defined in sib2/callsib.py even though sib2/callsib.py got called through sib1/call.py. However if one were to directly call sib1/call.py (after making appropriate changes to the imports) it throws an exception. Even though it worked when called by the script in its parent directory, it will not work if it believes itself to be on the top level of the package.

Answer 2

For siblings package imports, you can use either the insert or the append method of the [sys.path][2] module:

if __name__ == '__main__' and if __package__ is None:
    import sys
    from os import path
    sys.path.append( path.dirname( path.dirname( path.abspath(__file__) ) ) )
    import api

This will work if you are launching your scripts as follows:

python examples/example_one.py
python tests/test_one.py

On the other hand, you can also use the relative import:

if __name__ == '__main__' and if __package__ is not None:
    import ..api.api

In this case you will have to launch your script with the '-m' argument (note that, in this case, you must not give the '.py' extension):

python -m packageName.examples.example_one
python -m packageName.tests.test_one

Of course, you can mix the two approaches, so that your script will work no matter how it is called:

if __name__ == '__main__':
    if __package__ is None:
        import sys
        from os import path
        sys.path.append( path.dirname( path.dirname( path.abspath(__file__) ) ) )
        import api
    else:
        import ..api.api

Answer 3

You need to look to see how the import statements are written in the related code. If examples/example_one.py uses the following import statement:

import api.api

...then it expects the root directory of the project to be in the system path.

The easiest way to support this without any hacks (as you put it) would be to run the examples from the top level directory, like this:

PYTHONPATH=$PYTHONPATH:. python examples/example_one.py 

Answer 4

Here is another alternative that I insert at top of the Python files in tests folder:

# Path hack.
import sys, os
sys.path.insert(0, os.path.abspath('..'))