¶Importing a nested module does not create a shim

You can import a nested module using the typical dot notation: import os.path. This creates a binding in the current file-global scope called os. You must access the imported nested module (and its contents) using its full path: os.path.join.

Nothing unexpected so far. But at this point, there are a few possibilities:

os is just a shim object of some kind, and only contains the nested path module. You don't have access to any definitions in os unless you import explicitly that as well.

os is the actual os package. You have access to all of its definitions, as well as the path submodule, but not to any other submodules, unless you import them.

os is the actual os package. You have access to all of its definitions, the path submodule, and all other submodules in the package, but not any sub-submodules.

os is the actual os package. You have access to all of its definitions, the path submodule, and all other submodules and sub-submodules (etc) in the package.

I can't find if it's explicitly documented anywhere, but it seems Python implements option (2): importing os.path also implicitly imports os, but not any other submodules unless you explicitly import them.

¶A false start

Note that I first tried with logging—I thought it would be a better test since it contains more than one submodule.

But! This is a false positive. This behavior occurs because logging.config itself imports logging.handlers!

Python 3.12.7 (main, Oct  1 2024, 11:15:50) [GCC 14.2.1 20240910] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import logging
>>> logging
<module 'logging' from '/usr/lib/python3.12/logging/__init__.py'>
>>> logging.config
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'logging' has no attribute 'config'
>>> import logging.config
>>> logging
<module 'logging' from '/usr/lib/python3.12/logging/__init__.py'>
>>> logging.Logger
<class 'logging.Logger'>
>>> logging.config
<module 'logging.config' from '/usr/lib/python3.12/logging/config.py'>
>>> logging.config.fileConfig
<function fileConfig at 0x71a0d3dcdda0>
>>> logging.handlers
<module 'logging.handlers' from '/usr/lib/python3.12/logging/handlers.py'>
>>> logging.handlers.WatchedFileHandler
<class 'logging.handlers.WatchedFileHandler'>

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