Python - 使用带有 if/elif 语句的 while 循环

Question

I'm not sure why this isn't working, but I have a feeling it has something to do with how I've structured the while loop. I want the loop to continue only if the user inputs something other than the two choices they have. However, even when I test it with putting in either of the two correct choices, the while loop continues.

prompt = "> "

print "Welcome to the converter. What would you like \
to convert? (temp or distance)"
choice = raw_input(prompt)

while (choice != "temp" or choice != "distance"):
    print "Sorry, that's not an option"
    choice = raw_input(prompt)
if choice == "temp":
    print "temp"
elif choice == "distance":
    print "distance"

What am I missing here? Thanks in advance.

Answer 1

You want choice to be either "temp" or "distance", so your while condition should be that it can't (not be "temp" AND not be "distance"). Just substitute the or for and on the while condition.

prompt = "> "

print "Welcome to the converter. What would you like \
to convert? (temp or distance)"
choice = raw_input(prompt)

while (choice != "temp" and choice != "distance"):
    print "Sorry, that's not an option"
    choice = raw_input(prompt)
if choice == "temp":
    print "temp"
elif choice == "distance":
    print "distance"

The way you had it before the condition would always be true

Per suggestions below other ways you could write the while condition that would also work:

while not (choice == "temp" or choice == "distance"):

or

while (choice not in ('temp', 'distance')):

Take your pick.