"or" conditional in Python troubles

Question

I’m learning Python and I’m having a little bit of a problem. Came up with this short script after seeing something similar in a course I’m taking. I’ve used “or” with “if” before with success (it doesn’t show much here). For some reason I can’t seem to get this working:

test = raw_input("It's the flying circus! Cool animals but which is the best?")
x = test.lower()

if x == "monkey" or "monkeys":
    print "You're right, they are awesome!!"
elif x != "monkey" or "monkeys":
    print "I'm sorry, you're incorrect.", x[0].upper() + x[1:], "is not the right animal."

But this works great:

test = raw_input("It's the flying circus! Cool animals but which is the best?")
x = test.lower()

if x == "monkey":
    print "You're right, they are awesome!!"
elif x != "monkey":
    print "I'm sorry, you're incorrect.", x[0].upper() + x[1:], "is not the right animal."

Probably the or conditional does not fit here. But I’ve tried and, etc. I’d love a way to make this accept monkey or monkeys and everything else triggers the elif.

Asked By: Interrupt

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Source

Answer 1

Should be
if x == "monkey" or x == "monkeys":

Answered By: gkayling

Answer 2

Boolean expressions in most programming languages don’t follow the same grammar rules as English. You have to do separate comparisons with each string, and connect them with or:

if x == "monkey" or x == "monkeys":
    print "You're right, they are awesome!!"
else:
    print "I'm sorry, you're incorrect.", x[0].upper() + x[1:], "is not the right animal."

You don’t need to do the test for the incorrect case, just use else. But if you did, it would be:

elif x != "monkey" and x != "monkeys"

Do you remember learning about deMorgan’s Laws in logic class? They explain how to invert a conjunction or disjunction.

Answered By: Barmar

Answer 3

gkayling is correct. Your first if statement returns true if:

x == “monkey”

or

“monkeys” evaluates to true (it does since it’s not a null string).

When you want to test if x is one of several values, it’s convenient to use the “in” operator:

test = raw_input("It's the flying circus! Cool animals but which is the best?")
x = test.lower()

if x in ["monkey","monkeys"]:
    print "You're right, they are awesome!!"
else:
    print "I'm sorry, you're incorrect.", x[0].upper() + x[1:], "is not the right

Answered By: Rob Falck

"or" conditional in Python troubles

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