CODEWITHSUNDEEP
pythonwhile-loop
Eric K.
Eric K.

Reputation: 5

Exiting a while loop in Python

Here's the code I have question with:

isPet_list_elem = input("Pet?: ").lower()

# check if the input is either y or n
while isPet_list_elem != "y" or isPet_list_elem != "n":
    print("Please enter either 'y' or 'n'.")
    isPet_list_elem = input("Pet?: ").lower()

I keep thinking that the loop would end when I enter either "y" or "n", but the loop continues to ask me for another input even after entering either y or n.

I've tried using other while loop to do the same, but the result was the same. What should I do to avoid this error?

Upvotes: 0

Views: 88

Answers (5)

Wei
Wei

Reputation: 1

Include the following inside while loop:

    if isPet_list_elem == "y" or isPet_list_elem == "n":
            break

Upvotes: 0

luckyqiao
luckyqiao

Reputation: 52

If you enter "y", then isPet_list_elem != "n" is true; if you enter "n", then isPet_list_elem != "y" is true. And you use or in your code, so, if one expressin is true, the whole statement will be true.

you can use the following code instead:

while isPet_list_elem != "y" and isPet_list_elem != "n"

Upvotes: 0

vash_the_stampede
vash_the_stampede

Reputation: 4606

You can just do this and this will break the loop for y or n

while isPet_list_elem not in ('y','n'):

Upvotes: 1

bigwillydos
bigwillydos

Reputation: 1371

You are using the wrong logic. When you enter y or n with your code, the condition at the beginning of the loop comes out as True so it continues to execute. Change it to an and statement and once y or n is entered, the condition will be False.

isPet_list_elem = input("Pet?: ").lower()

# check if the input is either y or n
while isPet_list_elem != "y" and isPet_list_elem != "n":
    print("Please enter either 'y' or 'n'.")
    isPet_list_elem = input("Pet?: ").lower()

Upvotes: 0

XlbrlX
XlbrlX

Reputation: 763

It's Demorgan's law.

You can say: 

while isPet_list_elem != "y" and isPet_list_elem != "n"

or

while not (isPet_list_elem == "y" or isPet_list_elem == "n")

Upvotes: 2

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