[python] Import local function from a module housed in another directory with relative imports in Jupyter Notebook using Python 3

I have found that python-dotenv helps solve this issue pretty effectively. Your project structure ends up changing slightly, but the code in your notebook is a bit simpler and consistent across notebooks.

For your project, do a little install.

pipenv install python-dotenv

Then, project changes to:

+-- .env (this can be empty)
+-- ipynb
¦   +-- 20170609-Examine_Database_Requirements.ipynb
¦   +-- 20170609-Initial_Database_Connection.ipynb
+-- lib
    +-- __init__.py
    +-- postgres.py

And finally, your import changes to:

import os
import sys

from dotenv import find_dotenv


sys.path.append(os.path.dirname(find_dotenv()))

A +1 for this package is that your notebooks can be several directories deep. python-dotenv will find the closest one in a parent directory and use it. A +2 for this approach is that jupyter will load environment variables from the .env file on startup. Double whammy.