Importing modules in Python and __init__.py

Question

I have been reading about the function of __init__.py file. It is said that we need an empty __init__.py file in the folder which contains modules, so that these modules can be imported. However, I tried adding a folder path to PYTHONPATH (Environment Variable in Windows 7). Although this folder does not contain an __init__.py file, I can still import the modules from that folder. Could you please explain how these modules can be imported without the existence of an __init__.py?

Thanks,

Best regards

Answer 1

__init__.py turns a folder into a package. This is useful to create a sort of hierarchy of modules, where you can have import-statements like this:

import mymodule.cool.stuff 

This is not possible without packages.

Answer 2

If a directory (folder) contains a __init__.py file then it becomes a package. What you thought you read was not strictly correct, as you found. A package can be imported as if it was a module by itself, and any code in __init__.py is run, although it is often empty. Packages are a way of grouping multiple modules together, and you can load them using:

import package-name.module-name

Packages can also be nested, and often are. Look in the Lib directory under your Python software directory for many examples.