Flask session

A Flask session can be defined as data temporarily stored on a Flask server for the duration in which a user logs into a Flask server, and logs out. The session data is stored on top of cookies and signed by the server cryptographically.

templates\template.html

{% if time is defined %}
  <p>Session commenced at: {{time}}</p>
  <a href="/stop_session">stop session</a>
{% else %}
  <a href="/start_session">start session</a>
{% endif %}

server.py

from flask import *
from datetime import *

app = Flask("sessions in flask")

#session in Flask requires any secret key.
#this key encrypts cookies sent to browser.
#normally this lives outside of this file:
app.secret_key = "password1234"

@app.route("/")
def main():
    if "time_started" in session:
        return render_template("template.html",
                               time=session["time_started"])
    else:
        return render_template("template.html")

@app.route("/start_session")
def start_session():
    if "time_started" not in session:
        right_now = datetime.now()
        time_formatted = right_now.strftime("%A, %d %B %Y, %H:%M:%S")
        session["time_started"] = time_formatted
    return redirect("/")

@app.route("/stop_session")
def stop_session():
    if "time_started" in session:
        session.pop("time_started")
    return redirect("/")

app.run(debug=True)