Here's a really hack-y method of decoding multiple encoded Base64 strings. Useful for some very basic CTFs.

#!/usr/bin/env python3

import base64
from itertools import repeat

base64_string = input("Enter Base64 String: ")
decode_times = int(input("Enter number of times to decode: "))

for x in repeat(None, decode_times):
    base64_string = base64.b64decode(base64_string)

print (base64_string)

Your mileage may vary.