index.js

// import express JS module into app
// and creates its variable.
var express = require("express");
var app = express();
const fs = require("fs");
const { Buffer } = require("Buffer");
// Creates a server which runs on port 3000 and
// can be accessed through localhost:3000
app.listen(3000, function () {
  console.log("server running on port 3000");
});

// Function callName() is executed whenever
// url is of the form localhost:3000/name
app.get("/name", callName);

function callName(req, res) {
  // Use child_process.spawn method from
  // child_process module and assign it
  // to variable spawn
  var spawn = require("child_process").spawn;

  // Parameters passed in spawn -
  // 1. type_of_script
  // 2. list containing Path of the script
  // and arguments for the script

  // E.g : http://localhost:3000/name?firstname=Mike&lastname=Will
  // so, first name = Mike and last name = Will
  var process = spawn("python", [
    "./hello.py",
    req.query.firstname,
    req.query.lastname,
  ]);
  let myStream = fs.createWriteStream("image2.png");
  // Takes stdout data from script which executed
  // with arguments and send this data to res object
  process.stdout.on("data", async function (data) {
    let mybuffer = Buffer.from(data.toString(), "base64");
    fs.writeFileSync("image9.png", mybuffer);
  });
}