def num_generator(a, b):    #自然数生成器

    yield a

    while b > a:

        yield a + 1

        a += 1

def is_palindrome(num):

    '''检测回文数字，正数'''

    return str(num) == str(num)[::-1]

nums = num_generator(0,20)

result = filter(is_palindrome, nums)

print(list(result))