Passing data between Python and other languages

Data passed between two programming languages must be serialized.   Serializing data means taking a value, object, or data structure, and translating it into a format that can be stored or transmitted.  

Python <-> Javascript

Python and Javascript can pass data between them using AJAX requests via the Fetch API, and piping between local processes.   In JavaScript, you serials to JSON with JSON.stringify() and parse with JSON.parse().   In Python, you serials with json.dumps() and parse with json.loads().  

Python communication via AJAX can be done with XMLHttpRequest or the new Fetch API.  

Talking to Python from JavaScript (and Back Again!)

The image below shows a GET request from app.py processed by JavaScript within index.html running in the browser on the Flask web server.  

How to Get Python and JavaScript to Communicate Using JSON