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)