How to exclude characters when counting digits

[buran]

I didn't run time it.

import timeit
import string

my_string = 'DS80A98SD09a8SD098ASD098A09sd8c0a9SCNAfsdg8fbvdfad098098f00A'*1000

def count_func(s):
    return sum(c.isdigit() for c in s)


def smart_count_digits(my_string):
    orig_length = len(my_string)
    for digit in string.digits:
        my_string = my_string.replace(digit, '')
    return orig_length - len(my_string)

elapsed = timeit.timeit('count_func(my_string)', number=1000, setup='from __main__ import count_func, my_string')
print( 'count_func took {:.3f} sec'.format(elapsed))

elapsed = timeit.timeit('smart_count_digits(my_string)', number=1000, setup='from __main__ import smart_count_digits, my_string')
print('smart_count_digits took {:.3f} sec'.format(elapsed))

Output:
count_func took 15.112 sec
smart_count_digits took 1.181 sec