Import a library which is in a sibling of the current folder

Question

With the folder structure

lib/
    abcd/
        __init.py__
        lib.py
app.py

the code

from lib.abcd import lib

works. But with this file structure:

bin/
    app.py
lib/
    abcd/
        __init.py__
        lib.py

the code

from ..lib.abcd import lib     

gives an import error.

How to do the import properly when the library is in a sibling of the current folder? (or subfolder of a sibling folder)

I know that there might some hack that involves adding lib/ to the PATH, but is there an elegant Pythonic solution?

If not, is there a real internal reason to prevent users to do this simple import in a simple way?

Answer 1

Methods to do this

---

Method #1: Using the sys module: You can easily accomplish what you are trying to do using the sys module. To import the lib package, you can use one of the two codes listed below:

import sys
sys.path.append('<PATH_TO_LIB_FOLDER>')

from lib.abcd import lib

or

import sys
sys.path.insert(0, '<PATH_TO_LIB_FOLDER>')

---

Method #2: Using the os module: Another method is to use the os module. Here is an example code that imports the lib module using the os module by invoking the os.path.join method:

import os

path = os.path.join("<PATH>/lib/abcd", "lib")
from lib.abcd import lib

---

Method #3: Add the module to your PYTHONPATH: This is not the best method in most cases, but if you don't want to keep using the sys or os module to import lib, this is ideal. All you have to do is type this in your bash terminal:

export PYTHONPATH=<PATH_TO_LIB> python lib.py

Then in your python shell you can import it like this:

from lib.abcd import lib

---

Method #4: Combine the sys and os module (recommended): This is the most efficient method and will save you a lot of time. This code combines the os and sys module like this:

import sys, os
sys.path.append(os.path.abspath(os.path.join('..', 'lib')))

Then you can import your module with ease like this:

from lib.abcd import lib

---

How all the codes work:

All the codes above are very simple. All the examples except for "Method #3", add your module to the PYTHONPATH temporarily. "Method #3" on the other hand, adds the module to your PYTHONPATH permanently.