2018年6月20日

def is_odd(n):
    return n % 2 == 1

# 筛选出奇数
print(list(filter(is_odd, list(range(1, 11)))))

[1, 3, 5, 7, 9]

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


# 删除空格，空值和None
print(list(filter(not_empty, ['A', '', 'B', None, 'C', ' '])))

['A', 'B', 'C']

# 起始数是3的生成器
def _odd_iter():
    n = 1
    while True:
        n = n + 2
        yield n


# 筛选函数
def _not_divisible(n):
        # 不能被n整除，返回True
    return lambda x: x % n > 0

# 生成质数
def primes():
    yield 2
    it = _odd_iter()
    while True:
        n = next(it)
        yield n
        it = filter(_not_divisible(n), it)

# 打印1000以内的质数
for n in primes():
    if n < 1000:
        print(n)
    else:
        break

list(range(0))

[]

判断回数，回数是指从左向右读和从右向左读都是一样的数

#第一版
def is_palindrome(n):
    n_str = str(n)
    is_not = True
    if len(n_str) % 2 == 0:
        for i in range(len(n_str) // 2):
            is_not = is_not and n_str[0 + i] == n_str[-1 - i]
    else:
        for i in range((len(n_str) + 1) // 2):
            is_not = is_not and n_str[0 + i] == n_str[-1 - i]
    return is_not



# 测试:
output = filter(is_palindrome, range(1, 1000))
print('1~1000:', list(output))
if list(filter(is_palindrome, range(1, 200))) == [1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191]:
    print('测试成功!')
else:
    print('测试失败!')

1~1000: [1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 202, 212, 222, 232, 242, 252, 262, 272, 282, 292, 303, 313, 323, 333, 343, 353, 363, 373, 383, 393, 404, 414, 424, 434, 444, 454, 464, 474, 484, 494, 505, 515, 525, 535, 545, 555, 565, 575, 585, 595, 606, 616, 626, 636, 646, 656, 666, 676, 686, 696, 707, 717, 727, 737, 747, 757, 767, 777, 787, 797, 808, 818, 828, 838, 848, 858, 868, 878, 888, 898, 909, 919, 929, 939, 949, 959, 969, 979, 989, 999]
测试成功!

# 第二版
def is_palindrome(n):
    n_str = str(n)
    is_not = True
    for i in range(len(n_str)):
        is_not = is_not and n_str[i] == n_str[-1 - i]
    return is_not



# 测试:
output = filter(is_palindrome, range(1, 1000))
print('1~1000:', list(output))
if list(filter(is_palindrome, range(1, 200))) == [1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191]:
    print('测试成功!')
else:
    print('测试失败!')

1~1000: [1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 202, 212, 222, 232, 242, 252, 262, 272, 282, 292, 303, 313, 323, 333, 343, 353, 363, 373, 383, 393, 404, 414, 424, 434, 444, 454, 464, 474, 484, 494, 505, 515, 525, 535, 545, 555, 565, 575, 585, 595, 606, 616, 626, 636, 646, 656, 666, 676, 686, 696, 707, 717, 727, 737, 747, 757, 767, 777, 787, 797, 808, 818, 828, 838, 848, 858, 868, 878, 888, 898, 909, 919, 929, 939, 949, 959, 969, 979, 989, 999]
测试成功!

# 第三版
def is_palindrome(n):
    return str(n) == str(n)[::-1]



# 测试:
output = filter(is_palindrome, range(1, 1000))
print('1~1000:', list(output))
if list(filter(is_palindrome, range(1, 200))) == [1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191]:
    print('测试成功!')
else:
    print('测试失败!')

1~1000: [1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 202, 212, 222, 232, 242, 252, 262, 272, 282, 292, 303, 313, 323, 333, 343, 353, 363, 373, 383, 393, 404, 414, 424, 434, 444, 454, 464, 474, 484, 494, 505, 515, 525, 535, 545, 555, 565, 575, 585, 595, 606, 616, 626, 636, 646, 656, 666, 676, 686, 696, 707, 717, 727, 737, 747, 757, 767, 777, 787, 797, 808, 818, 828, 838, 848, 858, 868, 878, 888, 898, 909, 919, 929, 939, 949, 959, 969, 979, 989, 999]
测试成功!

判断回数，回数是指从左向右读和从右向左读都是一样的数

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