Can’t import my own modules in Python

I’m having a hard time understanding how module importing works in Python (I’ve never done it in any other language before either).

Let’s say I have:

myapp/__init__.py
myapp/myapp/myapp.py
myapp/myapp/SomeObject.py
myapp/tests/TestCase.py

Now I’m trying to get something like this:

myapp.py
===================
from myapp import SomeObject
# stuff ...

TestCase.py
===================
from myapp import SomeObject
# some tests on SomeObject

However, I’m definitely doing something wrong as Python can’t see that myapp is a module:

ImportError: No module named myapp

Answer

In your particular case it looks like you’re trying to import SomeObject from the myapp.py and TestCase.py scripts. From myapp.py, do

import SomeObject

since it is in the same folder. For TestCase.py, do

from ..myapp import SomeObject

However, this will work only if you are importing TestCase from the package. If you want to directly run python TestCase.py, you would have to mess with your path. This can be done within Python:

import sys
sys.path.append("..")
from myapp import SomeObject

though that is generally not recommended.

In general, if you want other people to use your Python package, you should use distutils to create a setup script. That way, anyone can install your package easily using a command like python setup.py install and it will be available everywhere on their machine. If you’re serious about the package, you could even add it to the Python Package Index, PyPI.