from random import choices
from datetime import datetime

time_init = datetime.now()
pattern = [chr(elem) for elem in range(ord('A'), ord('Z') + 1)] + [chr(elem) for elem in range(ord('a'), ord('z') + 1 )]

find_list = ["".join(choices(pattern, k=100)) for _ in range(100000)]
result_list = []
for i in range(1000):
    s = "".join(choices(pattern, k=20))
    for string in find_list:
        if s in string:
            result_list.append("{0} -> {1}".format(s, string))
            break

print(result_list)
print(datetime.now() - time_init)