# -*- coding:utf8 -*-
# Power by zuosc
# filter filter()把传入的函数依次作用于每个元素，然后根据返回值是True还是False决定保留还是丢弃该元素。
def is_odd(n):
    return n % 2 == 1


print(list(filter(is_odd, [1, 2, 3, 4, 5, 6, 7])))


def not_empty(s):
    return s and s.strip()


print(list(filter(not_empty, ['a', 'bb', None, 'cccc'])))

# 素数的获取


def _odd_iter():
    n = 1
    while True:
        n = n + 2
        yield n


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字
        yield n
        it = filter(_not_divisible(n), it)


for n in primes():
    if n < 1000:
        print(n)
    else:
        break


print('----------------------------------------')

# 回数的获取


def is_palindrome(n):
    return int(str(n)[::-1]) == n


print(list(filter(is_palindrome, range(1, 1000))))
