You'd be surprised how many times another person has a similar problem. You just need to know how to search for it. In this case, think of your numbers as strings because each character in a strings are iterable.
I wasn't sure if you'll ever have values that are different lengths so I assumed yes. To handle this case, I had to lean on a function in itertools I'd never heard of called zip_longest and applied it to this solution to sum the occurrences where the positional characters are different.
def compare_positional_chars(val1, val2):
# Import the required library
from itertools import zip_longest
# Force the value to string.
val1 = str(val1)
val2 = str(val2)
# Create key/value pairs of positional characters from each input.
zip_result = zip_longest(val1, val2)
# Count the number of pairs that don't have the same key and value.
return sum(1 for x,y in zip_result if x != y)
# Call the function in calculate field with your field names to be compared.
compare_positional_chars(!Field1!, !Field2!)
