flaskbaseapp/app.py

from flask import Flask, request, render_template
app = Flask(__name__)

@app.route('/')
def index():
    return render_template('modulo.html')

@app.route('/area_rettangolo', methods=['POST'])
def rectarea():
    area = int(request.form['base']) * int(request.form['altezza'])
    return render_template('area.html', area_calcolata=area)

if __name__ == '__main__':
    app.run()