Unreadable Notebook NotJSONError('Notebook does not appear to be JSON: u\'{\\n "cells": [\\n {\\n "cell_type": "...',)

Save yourself a headache. Open your .ipynb in any online JSON validator and it will tell you which lines have issues. I used this one.

This happened to me as well. I opened my data.ipynb file using notepad and found out it was blank.

I managed to recover my file by going into the hidden ipynb_checkpoints folder and copying data_checkpoint.ipynb out into my working directory.

In my Mac OS terminal

cd .ipynb_checkpoints
cp data-checkpoint.ipynb \..

Thankfully the codes were preserved. Hope this helps!

In my case, I am using GitHub to save and share my ipython files with my teammate. When there is a conflict in the code, I had to delete those lines indicating the changes in the conflicting code such as:

>>>>>>>>head
=============

and It works for me.