Add a loop until user inputs a valid answer?

Question

I want to add a loop to this:

question = raw_input("Reboot Y/N ")
if len(question) > 0 and question.isalpha():
    answer = question.upper()
    if answer == "Y":
        print "Reboot"
    elif answer == "N":
        print "Reboot Cancled"
    else:
        print "/ERROR/"

So if the user inputs anything else the error appears and sends them back to the question.

You realize that if the user types anything other than a letter, he's not going to get any response at all, right? Is that what you intended? — abarnert, Nov 28 '12 at 19:11
Why is this so heavily downvoted and closed? This seems like a common beginner question. — ShreevatsaR, Oct 20 '13 at 11:32
Canonical duplicate: https://stackoverflow.com/questions/23294658/asking-the-user-for-input-until-they-give-a-valid-response — tripleee, Feb 11 '21 at 10:04

score 6 · Answer 1 · edited Jan 01 '14 at 14:20

6

Add a while True at the top, and if user has entered correct output, break the loop: -

while True:
    question = raw_input("Reboot Y/N ")
    if len(question) > 0:
        answer = question.upper()
        if answer == "Y":
            print "Reboot"
            break
        elif answer == "N":
            print "Reboot Canceled"
            break
        else:
            print "/ERROR/"

edited Jan 01 '14 at 14:20

BenMorel

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answered Nov 28 '12 at 19:09

Rohit Jain

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Might want to remove that `and question.isalpha()` part, too. – martineau Nov 28 '12 at 19:15
@martineau.. Yeah that was in fact not needed. Thanks :) – Rohit Jain Nov 28 '12 at 19:16
Thank you everyone for the response, I'm a novice coder and new to the site so sorry for the very bad question :'( – Molly Nov 29 '12 at 02:27
@Molly.. You can mark this answer as accepted by clicking the arrow besides it. – Rohit Jain Nov 29 '12 at 05:26

score 0 · Answer 2 · answered Nov 28 '12 at 19:19

something like this:

answer={"Y":"Reboot","N":"Reboot cancled"} #use a dictionary instead of if-else
inp=raw_input("Reboot Y/N: ")

while inp not in ('n','N','y','Y') :  #use a tuple to specify valid inputs
   print "invalid input"
   inp=raw_input("Reboot Y/N: ")

print answer[inp.upper()]

output:

$ python so27.py

Reboot Y/N: foo
invalid input
Reboot Y/N: bar
invalid input
Reboot Y/N: y
Reboot

Add a loop until user inputs a valid answer?

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