How to exclude characters when counting digits

[gruntfutuk]

On my iPad:

print('smart:',timeit.timeit("smart_count_digits(my_string)", setup = "from __main__ import smart_count_digits, my_string", number = 1000))
print('count:',timeit.timeit("count_digits(my_string)", setup = "from __main__ import count_digits, my_string", number = 1000))
print('ick:',timeit.timeit("ick_count(my_string)", setup = "from __main__ import ick_count, my_string", number = 1000))

Output:
smart: 1.1727769580029417
count: 8.195804083981784
ick: 0.5881457919895183

ick_count is the winner.