hello.py
from flask import *
app = Flask(__name__)
@app.route("/")
def main():
return render_template("Hello Flask!")
app.run(debug=True)
.py
To launch, either double-click in Windows explorer, or open with Python:

Then navigate to port 5000 (default Flask port) of the loopback / localhost IP address in browser:
http://127.0.0.1:5000/