What is the Python equivalent to the C++ namespace?

The closest in spirit would be to use a module.

In a file lower_level.py you'd have

def do_stuff():
  pass

and then elsewhere you'd do:

import lower_level
lower_level.do_stuff()

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EDIT / addendums: That's the simple way. There's things like packages, where you'd have a folder lower_level, and inside that folder is an __init__.py identifying lower_level as a package. Inside that package you'd have .py files that'd be modules, or you put certain imports and declarations into the __init__.py. But it can also just remain empty. I guess packages would amount to nested namespaces.

- prog.py
\MyNameSpaceA
    - __init__.py # just an empty file
    - ObjA.py # A python Module
    \SubPackageB
       - __init__.py
       - ObjB.py # another python module