index.js

//We will have to create a childprocess in order tocall python script.
var spawn = require("child_process").spawn; 

//This process is called here.
var process = spawn('python',["./add.py",7,3] );

//We listen for 'data' event.
process.stdout.on('data', function (data) {
  console.log("Sum " + JSON.parse(data.toString()).sum);    
});