program to count number of 0's and 1's

Question

x = int(input('ENTER A NUMBER '))
count = 0
while x > 0:
    digit = x % 10
    if digit == 0 or digit == 1:
        count += 1
        x //= 10
print('THE NUMBER OF ONES OR ZEROES TOGETHER ARE: ', count)

If I run the above program with x//10 inside the if loop, the output only comes true if the user enters number containing 0's and 1's, any other input and I do not get the output at all.

x = int(input('ENTER A NUMBER '))
count = 0
while x > 0:
    digit = x % 10
    if digit == 0 or digit == 1:
        count += 1
    x //= 10
print('THE NUMBER OF ONES OR ZEROES TOGETHER ARE: ', count)

This code works just fine. I am confused.

Answer 1

In the first snippet, the call:

x //= 10

is made inside the if-statement , so it is only executed when the current digit being evaluated is either a 0 or a 1 . This means that when it doesn't meet this condition, x is never modified, so the same test is run over and over again - never ending.

In the second snippet, the same call is made outside of the scope of the if-statement so regardless of what the current digit is, x is modified to have one less character and the next character is evaluated rather than the same one as was happening in the first snippet.