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 

First, you should avoid having files with the same name as the module itself. It may break other imports.

When you import a file, first the interpreter checks the current directory and then searchs global directories.

Inside examples or tests you can call:

from ..api import api

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('..'))

I don’t yet have the comprehension of Pythonology necessary to see the intended way of sharing code amongst unrelated projects without a sibling/relative import hack. Until that day, this is my solution. For examples or tests to import stuff from ..api, it would look like:

import sys.path
import os.path
# Import from sibling directory ..api
sys.path.append(os.path.dirname(os.path.abspath(__file__)) + "/..")
import api.api
import api.api_key

Just in case someone using Pydev on Eclipse end up here: you can add the sibling’s parent path (and thus the calling module’s parent) as an external library folder using Project->Properties and setting External Libraries under the left menu Pydev-PYTHONPATH. Then you can import from your sibling, e. g. from sibling import some_class.

You don’t need and shouldn’t hack sys.path unless it is necessary and in this case it is not. Use:

import api.api_key # in tests, examples

Run from the project directory: python -m tests.test_one.

You should probably move tests (if they are api’s unittests) inside api and run python -m api.test to run all tests (assuming there is __main__.py) or python -m api.test.test_one to run test_one instead.

You could also remove __init__.py from examples (it is not a Python package) and run the examples in a virtualenv where api is installed e.g., pip install -e . in a virtualenv would install inplace api package if you have proper setup.py.

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

Tired of sys.path hacks?

There are plenty of sys.path.append -hacks available, but I found an alternative way of solving the problem in hand.

Summary

• Wrap the code into one folder (e.g. packaged_stuff)
• Create setup.py script where you use setuptools.setup(). (see minimal setup.py below)
• Pip install the package in editable state with pip install -e <myproject_folder>
• Import using from packaged_stuff.modulename import function_name

---

Setup

The starting point is the file structure you have provided, wrapped in a folder called myproject.

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

I will call the . the root folder, and in my example case it is located at C:tmptest_imports.

api.py

As a test case, let’s use the following ./api/api.py

def function_from_api():
    return 'I am the return value from api.api!'

test_one.py

from api.api import function_from_api

def test_function():
    print(function_from_api())

if __name__ == '__main__':
    test_function()

Try to run test_one:

PS C:tmptest_imports> python .myprojectteststest_one.py
Traceback (most recent call last):
  File ".myprojectteststest_one.py", line 1, in <module>
    from api.api import function_from_api
ModuleNotFoundError: No module named 'api'

Also trying relative imports wont work:

Using from ..api.api import function_from_api would result into

PS C:tmptest_imports> python .myprojectteststest_one.py
Traceback (most recent call last):
  File ".teststest_one.py", line 1, in <module>
    from ..api.api import function_from_api
ValueError: attempted relative import beyond top-level package

---

Steps

1. Make a setup.py file to the root level directory

---

The contents for the setup.py would be*

from setuptools import setup, find_packages

setup(name='myproject', version='1.0', packages=find_packages())

2. Use a virtual environment

---

If you are familiar with virtual environments, activate one, and skip to the next step. Usage of virtual environments are not absolutely required, but they will really help you out in the long run (when you have more than 1 project ongoing..). The most basic steps are (run in the root folder)

• Create virtual env
  • python -m venv venv
• Activate virtual env
  • source ./venv/bin/activate (Linux, macOS) or ./venv/Scripts/activate (Win)

To learn more about this, just Google out "python virtual env tutorial" or similar. You probably never need any other commands than creating, activating and deactivating.

Once you have made and activated a virtual environment, your console should give the name of the virtual environment in parenthesis

PS C:tmptest_imports> python -m venv venv
PS C:tmptest_imports> .venvScriptsactivate
(venv) PS C:tmptest_imports>

and your folder tree should look like this**

.
├── myproject
│   ├── api
│   │   ├── api_key.py
│   │   ├── api.py
│   │   └── __init__.py
│   ├── examples
│   │   ├── example_one.py
│   │   ├── example_two.py
│   │   └── __init__.py
│   ├── LICENCE.md
│   ├── README.md
│   └── tests
│       ├── __init__.py
│       └── test_one.py
├── setup.py
└── venv
    ├── Include
    ├── Lib
    ├── pyvenv.cfg
    └── Scripts [87 entries exceeds filelimit, not opening dir]

3. pip install your project in editable state

---

Install your top level package myproject using pip. The trick is to use the -e flag when doing the install. This way it is installed in an editable state, and all the edits made to the .py files will be automatically included in the installed package.

In the root directory, run

pip install -e . (note the dot, it stands for "current directory")

You can also see that it is installed by using pip freeze

(venv) PS C:tmptest_imports> pip install -e .
Obtaining file:///C:/tmp/test_imports
Installing collected packages: myproject
  Running setup.py develop for myproject
Successfully installed myproject
(venv) PS C:tmptest_imports> pip freeze
myproject==1.0

4. Add myproject. into your imports

---

Note that you will have to add myproject. only into imports that would not work otherwise. Imports that worked without the setup.py & pip install will work still work fine. See an example below.

---

Test the solution

Now, let’s test the solution using api.py defined above, and test_one.py defined below.

test_one.py

from myproject.api.api import function_from_api

def test_function():
    print(function_from_api())

if __name__ == '__main__':
    test_function()

running the test

(venv) PS C:tmptest_imports> python .myprojectteststest_one.py
I am the return value from api.api!

---

* See the setuptools docs for more verbose setup.py examples.

** In reality, you could put your virtual environment anywhere on your hard disk.

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.

I made a sample project to demonstrate how I handled this, which is indeed another sys.path hack as indicated above. Python Sibling Import Example, which relies on:

if __name__ == '__main__': import os import sys sys.path.append(os.getcwd())

This seems to be pretty effective so long as your working directory remains at the root of the Python project.

1. Project

1.1 User

1.1.1 about.py

1.1.2 init.py

1.2 Tech

1.2.1 info.py

1.1.2 init.py

Now, if you want to access about.py module in the User package, from the info.py module in Tech package then you have to bring the cmd (in windows) path to Project i.e.
**C:UsersPersonalDesktopProject>**as per the above Package example. And from this path you have to enter, python -m Package_name.module_name
For example for the above Package we have to do,

C:UsersPersonalDesktopProject>python -m Tech.info

Imp Points

1. Don’t use .py extension after info module i.e. python -m Tech.info.py
2. Enter this, where the siblings packages are in the same level.
3. -m is the flag, to check about it you can type from the cmd python –help

for the main question:

call sibling folder as module:

from .. import siblingfolder

call a_file.py from sibling folder as module:

from ..siblingfolder import a_file

call a_function inside a file in sibling folder as module:

from..siblingmodule.a_file import func_name_exists_in_a_file

The easiest way.

go to lib/site-packages folder.

if exists ‘easy_install.pth’ file, just edit it and add your directory that you have script that you want make it as module.

if not exists, just make it one…and put your folder that you want there

after you add it…, python will be automatically perceive that folder as similar like site-packages and you can call every script from that folder or subfolder as a module.

i wrote this by my phone, and hard to set it to make everyone comfortable to read.

I wanted to comment on the solution provided by np8 but I don’t have enough reputation so I’ll just mention that you can create a setup.py file exactly as they suggested, and then do pipenv install --dev -e . from the project root directory to turn it into an editable dependency. Then your absolute imports will work e.g. from api.api import foo and you don’t have to mess around with system-wide installations.

Documentation

in your main file add this:

import sys
import os 
sys.path.append(os.path.abspath(os.path.join(__file__,mainScriptDepth)))

mainScriptDepth = the depth of the main file from the root of the project.

Here is your case mainScriptDepth = "../../". Then you can import by specifying the path (from api.api import * ) from the root of your project.

If you’re using pytest then the pytest docs describe a method of how to reference source packages from a separate test package.

The suggested project directory structure is:

setup.py
src/
    mypkg/
        __init__.py
        app.py
        view.py
tests/
    __init__.py
    foo/
        __init__.py
        test_view.py
    bar/
        __init__.py
        test_view.py

Contents of the setup.py file:

from setuptools import setup, find_packages

setup(name="PACKAGENAME", packages=find_packages())

Install the packages in editable mode:

pip install -e .

The pytest article references this blog post by Ionel Cristian Mărieș.

For readers in 2023: If you’re not confident with pip install -e :

TL;DR: A script(usually an entry point) can only import anything the same or below its level.

Consider this hierarchy, as recommended by an answer from Relative imports in Python 3:

MyProject
├── src
│   ├── bot
│   │   ├── __init__.py
│   │   ├── main.py
│   │   └── sib1.py
│   └── mod
│       ├── __init__.py
│       └── module1.py
└── main.py

The content of main.py, which is the starting point and we use absolute import (no leading dots) here:

from src.bot import main


if __name__ == '__main__':
    main.magic_tricks()

The content of bot/main.py, which takes advantage of explicit relative imports:

from .sib1 import my_drink                # Both are explicit-relative-imports.
from ..mod.module1 import relative_magic

def magic_tricks():
    # Using sub-magic
    relative_magic(in=["newbie", "pain"], advice="cheer_up")
    
    my_drink()
    # Do your work
    ...

Now here comes the reasoning:

• When executing python MyProject/main.py, the path/to/MyProject is added into the sys.path.
• The absolute import import src.bot will read it.
• The from ..mod part means it will go up one level to MyProject/src.
  • Can we see it? YES, since path/to/MyProject is added into the sys.path.

So the point is:

We should put the main script next to MyProject/src. This way you can always run it as simple as python main.py and it will always import the entire src tree correctly, and all files inside src will all have a sweet src as the top-level scope.

What if you want to run any file under src/ as a script?

Then you should use the syntax python -m and take a look at my another post: ModuleNotFoundError: No module named ‘sib1’

The problem:

You simply can not get import mypackage to work in test.py. You will need either an editable install, change to path, or changes to __name__ and path

demo
├── dev
│   └── test.py
└── src
    └── mypackage
        ├── __init__.py
        └── module_of_mypackage.py

--------------------------------------------------------------
ValueError: attempted relative import beyond top-level package

The solution:

import sys; sys.path += [sys.path[0][:-3]+"src"]

Put the above before attempting imports in test.py. Thats it. You can now import mypackage.

This will work both on Windows and Linux. It will also not care from which path you run your script. It is short enough to slap it anywhere you might need it.

Why it works:

The sys.path contains the places, in order, where to look for packages when attempting imports if they are not found in installed site packages. When you run test.py the first item in sys.path will be something like /mnt/c/Users/username/Desktop/demo/dev i.e.: where you ran your file. The oneliner will simply add the sibling folder to path and everything works. You will not have to worry about Windows vs Linux file paths since we are only editing the last folder name and nothing else. If you project structure is already set in stone for your repository we can also reasonably just use the magic number 3 to slice away dev and substitute src