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pythonwhile-loopraw-input

Python: Repeating a function when raw_input is not valid

I'm want to be able to determine if an input is valid. I have:

servqual = raw_input(">").lower()
while servqual != "great" or "good" or "lacking" or "poor":
    print "I didn't understand that. Please try again."
    servqual = raw_input(">").lower()

However, whenever I run it through the loop it always assumes True, even if I input a valid answer. I've looked over different answers but none of them seem to work in this scenario.

Solution 
  • servqual != "great" or "good" or "lacking" or "poor"

    is equivalent to 

    (servqual != "great") or "good" or "lacking" or "poor"

    And since Strings are considered True, you are always getting it True

    The correct way to do it is

    servqual != "great" and servqual != "good" and servqual != "lacking" and servqual != "poor"

    or 

    servqual not in ("great", "good", "lacking", "poor")

    Your final code will look like

    servqual = raw_input(">").lower()
while servqual not in ("great", "good", "lacking", "poor"):
    print "I didn't understand that. Please try again."
    servqual = raw_input(">").lower()

    You can further improve it by using following construct.

    while raw_input(">").lower() not in ("great", "good", "lacking", "poor"):
    print "I didn't understand that. Please try again."