I have written this code in Flask

ans = 999
@app.route('/', methods=['POST', 'GET'])
def home():flag = 0global anssession["ans"] = 0if (request.method == "POST"):jsdata = request.form['data']flag = 1session['jsdata'] = jsdataif (flag == 1):ans = get_data(session['jsdata'])return render_template('/index.html',ans=ans)return render_template('/index.html',ans=ans)

When the value of flag was 0, in index.html it shows 999, but when value of flag changes to 1 and if condition is executed index.html still show value 999 not the values it got from function. and when I print the and in if condition for debugging it shows correct value.

You really don't need flag at all, it is confusing the entire logic:

@app.route('/',methods = ['POST','GET'])
def home():if request.method == "POST":jsdata = request.form['data']session['jsdata']=jsdatasession['ans'] = get_data(session['jsdata'])ans = session.get('ans', 999) # try to get it from the session,# if fails, set it to 999 default valuereturn render_template('/index.html', ans=ans)