Can someone explain __all__ in Python?

Question

I have been using Python more and more, and I keep seeing the variable `__all__` set in different `__init__.py` files. Can someone explain what this does?

Answer 1

Hello! The expression "__all__" deals with modules and how a file gets imported by other files. It has a twofold purpose:

1. It gives the user of the file information about the code - the the references contained within __all__ are publicly available, that they are intended to be used and that they should not change during execution.
2. When importing a file as a module, __all__ defines which references should be imported when using the wildcard import, or import *.

Generally speaking, the practice of using __all__ is designed to make understanding and using a Python module easier.

An excellent reference if you are looking to explore __all__ further might be: https://stackoverflow.com/questions/44834/can-someone-explain-all-in-python, the third response from the top provides the most accurate and detailed response to this question.

I hope you find this helpful!