python flask变量不会更新

Question

My flask program (simulation in the view) runs in the following order (detailed code is also attached):

1> read my variable 'tx_list' from session. tx_list = session.get('tx_list', None)

2> for t in tx_list: do someting with t.

3> store tx_list in session: session['tx_list'] = tx_list

The reason I use session is because I want to change 'tx_list' every time I invoke this 'simulation' function.

The problem now is that if I print (console.log(tx_list)) in the front-end, it only updates itself a few times. But in the same time, when I print the values in the simulation function, it always updates. So I suspect the problem is because of the session???

I've tried to add another 'time_now' variable in the simulation function, which is independent of session. Then in the front-end (html) always updates 'time_now'. So the problem must be because of the usage of session??? How can update my 'tx_list' if session is not the best way to do it?

-------------------code is below----------------------------

My view is like below: In my view, I simply read my var 'tx_list' from session, do something with it, then store it back to the session.

@app.route('/simulation/<param>')
def simulation(param):
    tx_list = session.get('tx_list', None)
    today = date.today()
    if t0 == '0':
        time_now = today.strftime("%Y-%m-%d %H")
    else:
        time_now = (today + relativedelta(hours=int(param))).strftime("%Y-%m-%d %H")

    return_val = jsonify({'time':time_now, 'tx_list':tx_list_0})
    for t in tx_list:
        ###########I have my code here to change t.
        print(t)
    session['tx_list'] = tx_list
    return return_val

Answer 1

problem solved once I installed Flask-Session and initilize it.

I feel puzzled why it updates OK for only a few times without installing the module.