python - How to fix "Attempted relative import in non-package" even with __init__.py

I'm trying to follow PEP 328, with the following directory structure:

pkg/
  __init__.py
  components/

    core.py
    __init__.py
  tests/
    core_test.py
    __init__.py

In core_test.py I have the following import statement

from ..components.core import GameLoopEvents

However, when I run, I get the following error:

tests$ python core_test.py 
Traceback (most recent call last):
  File "core_test.py", line 3, in 
    from ..components.core import GameLoopEvents
ValueError: Attempted relative import in non-package

Searching around I found "relative path not working even with __init__.py" and "Import a module from a relative path" but they didn't help.

Is there anything I'm missing here?

Answer

Yes. You're not using it as a package.

python -m pkg.tests.core_test