CODEWITHSUNDEEP
pythonpython-3.x
ih16
ih16

Reputation: 47

if statement somehow always true

I am trying to learn python, and currently I am trying to build a ticket machine that in this case simulates a payment step. because it is a simulation for demonstration purposes I ask the user through an Boolean input to enter True or false. for some reason when I enter False, it will still be interpreted as True. Below is my code:

def payment():
    global tries
    print("Payment can be done by PIN. Please follow the instructions on the payment terminal\n")
    time.sleep(2)
    payment_succeeded = bool(input("for demonstration purpose: did the payment succeed?"))
    if payment_succeeded is True:
        print("Payment succeeded.\n")
        trip_time()
        time.sleep(1)
    elif tries < 3:
        tries +=1
        print("Payment Failed. please try again\n")
        time.sleep(0.5)
        payment()
    else:
        print("Payment has failed. Stopping purchase.\n")

the global "tries" variable has a value of 1 by default

Upvotes: 0

Views: 5920

Answers (1)

Martijn Pieters
Martijn Pieters

Reputation: 1121296

bool() does not translate 'False' to False. It only looks at the truth value of the string, and only the empty string is considered false.

So, entering anything other than an empty string is considered true:

>>> bool(input(''))
Howdy!
True
>>> bool(input(''))  # Hitting enter results in an empty string

False

You'd be better off testing for certain strings:

response = input("for demonstration purpose: did the payment succeed?")
payment_succeeded = response.lower() in ('y', 'yes', 'it did', 'true', 'you betcha')
if payment_succeeded:   # no need for "is True" here

Now typing anything other than one of the expected strings will result in payment_succeeded being set to False.

You probably want to limit that a little more by providing expected input, and re-ask if that's not given:

while True:
    response = input("for demonstration purpose: did the payment succeed, yes or no?").lower()
    if response in ('y', 'yes', 'n', 'no'):
        payment_succeeded = response in ('y', 'yes')
        break
    print('Sorry, I did not understand that input, please try again.')

Upvotes: 3

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