Importing modules and packages

In the simplest case, a module is defined by a file module.py which contains the definitions of the module contents.

Alternatively, it can be defined by a folder module which contains a file __init__.py which contains the definitions of the module contents. Such a folder-module is also called a package¹, and the module-folder can contain other module-files or -folders, which define submodules or subpackages of the package.

For Python to be able to import a module, the module-file or top-level module-folder must be contained in one of the folders listed in sys.path.

In the statement import module, ‘module’ is the module’s name, which is used to find the file or folder. If the import is successful, a module object is created and assigned to the variable module.

With the statement import module as mod the module ‘module’ is imported, and the module object is assigned to the variable mod.

Footnotes

1. This is not to be confused with a distribution package. There are also namespace packages which do not have an __init__.py file.