substring permutations

from collections import defaultdict


class Solution:
    def compare_dicts(self, d1, d2):
        for key in d1.keys():
            if d1.get(key) != d2.get(key)  :
                return False
        return True

    def checkInclusion(self, s1: str, s2: str) -> bool:

        ls1 = len(s1);    ls2 = len(s2)
        s1_dict = defaultdict(int); s2_dict = defaultdict(int)

        for a in s1:
            s1_dict[a] += 1

        for a in s2[:ls1]:
            s2_dict[a] += 1


        if self.compare_dicts(s1_dict, s2_dict):
            return True



        for i in range(1,ls2-ls1+1):
            s2_dict[s2[ls1 - 1 + i ]] += 1
            s2_dict[s2[i-1]]      -= 1
            if self.compare_dicts(s1_dict, s2_dict):
                return True