Understanding Python's Import Engine

[MysticaL]

Hi,

I have a question pertaining to importing post python 3.4 (I am using python 3.8). It is my understanding that the import engine will internally invoke meta path finders in sys.meta_path, of which the third PathFinder is used to find modules using sys.path. Given the following file structure, with "test" and "a" being namespace packages,

example/test/a/b.py

If I run an interpreter with cwd as example, the following code fails:

>>> import test.a
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'test.a'

My question is, since the test builtin does not have a module "a", why does the third PathFinder fail to find the module, as the FileFinder with cwd should be able to locate the module?

[snippsat]

example will be the package_name at top level,so you most import from example.
Let say b.py is:

def foo():
    return 42

Import test.

E:\div_code
λ ptpython
>>> import example.test.a.b
>>> example.test.a.b.foo()
42

>>> # Using from
>>> from example.test.a import b
>>> b.foo()
42

For this to work most example folder with sub-folder be in sys.path of Python version used eg i use Python 3.7 here.