Access nodule imported from another module in Python 3

I have the following Python 3 project:

- main.py
- mylib
    | - foo.py
    | - bar.py
    | - last.py

In foo.py, I am using bar.py that I imported using absolut import (import mylib.bar).

Now in my main.py I have the following:

import mylib.foo
import mylib.last

result1 = mylib.foo.func()
result2 = mylib.last.func()
result3 = mylib.bar.func()

And this code does not throw any error and I do not understand why. I did not import mylib.bar in the main.py so the last line should not work. mylib.bar is imported in mylib.foo which itself is imported by main.py but isn't namespace supposed to be separated ? Why is it possible to use mylib.bar without importing in the main.py ?

mylib.foo is also using numpy, but numpy is not available in main.py, therefore why is mylib.bar available ?

Same behavior is also observed with relative import. I also tried to create __init__.py file.

EDIT:
I also changed the architecture to:

- main.py
- foo.py
- bar.py
- last.py

I this case, bar is no longer available in the main.py when importing foo. The behavior is different and seems to be related to the use of a subfolder.

In Python, when a module is imported, its code is executed and the resulting namespace is stored in sys.modules. When you import mylib.foo, Python will execute the code in mylib/foo.py, which in turn imports mylib.bar. Since mylib.bar has already been imported (because it was imported by mylib.foo), Python will simply return the existing namespace from sys.modules.

Therefore, when you later import mylib.last in main.py, Python will execute the code in mylib/last.py, which has access to mylib.bar because it has already been imported by mylib.foo.

As for numpy, it is possible that it is imported by mylib.foo but not explicitly imported by mylib.last. In this case, mylib.last can still access numpy through the existing namespace in sys.modules. However, if mylib.last tries to import numpy explicitly, it will fail because numpy has not been imported in that module's namespace.

Regarding the use of relative imports, it is important to make sure that the current package is properly defined by including an init.py file in the package directory. If this file is missing, Python will treat the package as a regular directory and relative imports may not work as expected.