Try/Except clauses not working?

[ensbana]

Would be great if someone could tell me why the Except clause doesn’t catch the exception below. Thanks.

def collatz(number):
    try:
        if number % 2 == 0:
            m = number // 2
            print(m)
            return(m)
        else:
            m = 3 * number + 1
            print(m)
            return(m)
    except ValueError:
        print('Error: Must enter an integer')


n = input('Enter number: \n')
# n = int(n)
while n != 1:
    n = collatz(n)

Error:
Enter number: 
15
Traceback (most recent call last):
  File "/Users/admin/PycharmProjects/hello/collatz.py", line 18, in <module>
    n = collatz(n)
  File "/Users/admin/PycharmProjects/hello/collatz.py", line 3, in collatz
    if number % 2 == 0:
TypeError: not all arguments converted during string formatting