from flask import jsonify, render_template, request from js_example import app @app.route("/", defaults={"js": "plain"}) @app.route("/") def index(js): return render_template("{0}.html".format(js), js=js) @app.route("/add", methods=["POST"]) def add(): a = request.form.get("a", 0, type=float) b = request.form.get("b", 0, type=float) return jsonify(result=a + b)