My code is not working, giving: AttributeError: 'int' object has no attribute 'upper'

I'm following this course on my laptop by typing exactly what Ken has on the workspace, but when I ran the code, I'm getting error, below is my code and the error:

CODE:

import datetime

answer_format = '%m/%d' link_format = '%b_%d' link = 'https://en.wikipedia.org/wiki/{}'

while True: answer = input("What date would you like? Please use the MM/DD format. Enter 'quit' to quit. ") if answer.upper() == 'QUIT': break

try:
    date = datetime.datetime.strptime(answer, answer_format)
    output = link.format(date.strftime(link_format))
    print(output)
except ValueError:
    print("That's not a valid date. Pleast try again")

ERROR:

{ Python } » python wiki.py /c/wamp64/www/Python 1 What date would you like? Please use the MM/DD format. Enter 'quit' to quit. 12/25 Traceback (most recent call last): File "wiki.py", line 9, in <module> if answer.upper() == 'QUIT': AttributeError: 'int' object has no attribute 'upper'