Python有关埃筛法如何改进

class Solution:
    def countPrimes(self, n: int) -> int:
        if str(n) in '01':
            return 0
        else:
            s=0
            m=n-1
            res=list(range(1,m+1))#0,1,2,3...100
            res=['= =']+res#使得数字i对应的下标就是i
            for i in range(2,int(m**0.5)+1):
                index=2
                while i*index<=m:
                    res[i*index]=None
                    index+=1
            print(res)
            for j in range(1,m+1):
                if res[j]!=None:
                    s+=1
            return s-1#1不是素数

代码还是超时到3w多的测试用例