Add a loop until user inputs a valid answer? [closed]

Answer 1

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/"

Answer 2

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