sieve 筛选法

def _odd_iter():
    n = 1
    while True:
        n = n + 2
        yield n #2把偶数都筛选了

def _not_divisible(n):
    return lambda x: x % n > 0

def primes():
    yield 2
    it = _odd_iter() # 初始序列
    while True:
        n = next(it) # 返回序列的第一个数
        yield n
        it = filter(_not_divisible(n), it) # 构造新序列

def sieve(m):
    s=[]
    for n in primes():
        if n < m:
            s.append(n)
        else:
            break
    return s
print(sieve(100))
输出：
[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97]