How can I import classes into other files?

I've got a file structure like this:

/app/sense/abstract/__init__.py
/app/sense/abstract/sensor.py
/app/sense/__init__.py
/app/sense/gps.py
/app/components.py
/app/main.py
/tests/unit/__init__.py
/tests/unit/context.py
/tests/unit/test_sense.py

sensor.py defines an abstract base class Sensor used by gps.py to shape a GPS class.

The intent of components.py is to facilitate
importing all classes in the subfolders in one line. The only line of code so far is:

from .sense.gps import GPS

The intent of context.py is to allow me to import classes for unit testing. It currently has the following lines of code:

from pathlib import Path
import sys

path = Path(__file__).resolve().parent.parent.parent
sys.path.insert(0, path)

import app.components as avc

And finally the test_sense.py class includes code to test whether the GPS implements Sensor.

The problem I'm having is that: whenever I try to run the test_sense.py file, I get ModuleNotFoundError, saying 'app' doesnt exist. How can I get around that?

The error occurs because the 'app' package is not in the Python path when running the test_sense.py file. One way to fix this is to add the 'app' package to the Python path in the test_sense.py file, similar to what is done in the context.py file. Here is how you can modify your test_sense.py file to add the 'app' package to the Python path:

import sys
from pathlib import Path

# Add the parent directory of the 'tests' directory to the Python path
sys.path.append(str(Path(__file__).resolve().parents[2]))

# Import the GPS class from the 'app' package
from app.sense.gps import GPS

# Import the Sensor class from the 'app' package
from app.sense.abstract.sensor import Sensor

# Define the test class
class TestGPS:

    # Test that GPS implements Sensor
    def test_implements_sensor(self):
        assert issubclass(GPS, Sensor)

This code adds the parent directory of the 'tests' directory to the Python path, which should allow Python to find the 'app' package. Then, it imports the GPS and Sensor classes from the 'app' package and defines the test class as before.