I was stuck with this problem too, and your work inspired me a lot.

Eventually, I simply use

for i in range(len(s)):
        if s[i].isdigit():
            if not s[i:].isdigit():
                return False
                break

s[i+1:].isalpha()

it would automatically return 'False' if there is only one non-0 digit (i.e. s[i]) at the end of the plate.