从调用其他模块的python文件导入模块

Question

I am trying to run a specific code, now it requires the following importing of the Python file and I am getting an error, I have constructed a toy example to illustrate the problem. I am running on Python version 3.6.3.
Consider the following folder structure.

root
  |- outside.py
  |- folA
       |- __init__.py
       |- inside.py
       |- folB
            |- __init__.py
            |- eveninside.py

Now the contents of these files are as follows.

outside.py

import folA.inside
print("Outside")

inside.py

import folB.eveninside
print("Inside")

eveninside.py

print("Even Inside")   #All inits are empty

Now when I run inside.py things run perfectly well and have expected outputs. But when I run outside.py there is an error saying "no module named folB". I have tried appending the system path but there are no changes. Please explain me how to resolve this.

Answer 1

This just come from the fact python goes look module from python path. Here when you launch outside he try to see if there is a folB in your directory where is outside.py.

Two solutions.

1. You use sys.path.append in inside.py to add the directory where is folA as a place to look for when trying to import module. I don't know how good practice it is.

2. In your case you can just write in inside.py `import folA.folB.eveninside. But obviously it won't work when you launch inside.py. In this case you have the first solution.

Answer 2

If you only wish to run the program from the outside.py, you can add this code to your includes in outside.py:

import os
import sys
sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), '.')))

and add a context.py to each level of your package structure with the following code:

import os
import sys
path = os.path.abspath(os.path.join(os.path.dirname(__file__), '..', '..'))
sys.path.insert(0, path)

_ = ''

you can then import this into your code to make it aware of the package structure. ie inside.py would have from .context import _

Disclaimer: This code came from someone else but I'm unsure who. Possibly this article . I am certain a better practice exist, but I have found this to work and the context.py makes a great place to keep constants in a central location. just import them instead of the underscore