python importing from subfolders

Question

When I import a subdirectory and assign it a variable name, why am I then unable to import modules from this subdirectory via the variable name?

Eg my directory structure is:

root\
    f1\
        f2\
            m1.py

when I do the following, everything is fine:

from f1.f2 import m1

But when I do the following, python interprets the from selection as a module and throws an error:

import f1.f2 as f

from f import m1

Error msg: ModuleNotFoundError: No module named 'f'

Why is f interpreted as a module and not the subdirectory f2 contained in f1?

Answer 1

The python grammar doesn't allow expressions after from :

import f1.f2 as f
from f import m1

f in the second line is a variable expression, and the Python grammar ( https://docs.python.org/3/reference/grammar.html ) thinks it has found a NAME , which is then fed to the import machinery to find a module named f :

Error msg: ModuleNotFoundError: No module named 'f'

You could do

import f1.f2 as f
m1 = f.m1

instead...

Answer 2

You need to create a init .py module in your package. Python recognizes such folders as packages.

Create an init .py file in the root folder, the f1 folder, and the f2 folder.

Answer 3

Whenever you use from or import , Python is looking for a module with the name that you are passing. You have to first import from the actual module name and then use your variables.

Example:

>>> import random as ran
>>> from ran import *      ## we cannot import from the variable
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'ran'
>>> ran.randint(1, 10)     ## but we now can use our variable 
8
>>>