Python testing whether a string is one of a certain set of values

Question

I'm learning python on codecademy and my current task is this:

Write a function, shut_down, that takes one parameter (you can use anything you like; in this case, we'd use s for string). The shut_down function should return "Shutting down..." when it gets "Yes", "yes", or "YES" as an argument, and "Shutdown aborted!" when it gets "No", "no", or "NO".

If it gets anything other than those inputs, the function should return "Sorry, I didn't understand you."

Seemed easy to me but somehow I still can't do it.

My code I made to test the function:

def shut_down(s):
    if s == "Yes" or s == "yes" or s == "YES":
        return "Shutting down..."
    elif s == "No" or "no" or "NO":
        return "Shutdown aborted!"
    else:
        return "Sorry, I didn't understand you."

i = input("Do you want to shutdown?")
print(i) #was to test the input
print(shut_down(i)) #never returns "Sorry, I didn't understand you"

It works fine for the no's and yes', but somehow if I put a space before any yes or even if I just type in "a" it prints "Shutdown aborted!" although it should print "Sorry, I didn't understand you".

What am I doing wrong?

Answer 1

You forgot to write s == "no" in your first elif:

def shut_down(s):
    if s == "Yes" or s == "yes" or s == "YES":
        return "Shutting down..."
    elif s == "No" or "no" or "NO":             # you forgot the s== in this line
        return "Shutdown aborted!" 
    else:
        return "Sorry, I didn't understand you."

Do this:

def shut_down(s):
    if s == "Yes" or s == "yes" or s == "YES":
        return "Shutting down..."
    elif s == "No" or s == "no" or s == "NO":       # fixed it 
        return "Shutdown aborted!"
    else:
        return "Sorry, I didn't understand you."

This is because:

elif s == "No" or "no" or "NO":  #<---this
elif s == "No" or True or True:  #<---is the same as this

Since this is the accepted answer I'll elaborate to include standard practices: The convention for comparing strings regardless of capitalization (equalsIgnoreCase) is to use .lower() like this

elif s.lower() == "no":