def arithemtic_sequence_based_generator(first=0, step=1, sequence_count=10):
    for index in range(0, sequence_count):
        yield first + index * step
        index += 1

if __name__ == "__main__":
    generator = arithemtic_sequence_based_generator(first=0, step=5, sequence_count=10)
    for number in generator:
        print(number, end=" ")

"""
等差數(shù)列實(shí)現(xiàn)。
"""

class ArithmeticProgression:

    def __init__(self, begin, step, end=None):
        self.begin = begin
        self.step = step
        self.end = end   # None -> 無(wú)窮數(shù)列

    def __iter__(self):
        result = type(self.begin + self.step)(self.begin)
        forever = self.end is None
        index = 0
        while forever or result < self.end:
            yield result
            index += 1
            result = self.begin + self.step * index

if __name__ == '__main__':
    ap = ArithmeticProgression(0, 1, 3)
    print(ap)
    # print(list(ap))
    a = iter(ap)
    print(next(a))

def aritprog_gen(begin, step, end=None):
    result = type(begin + step)(begin)
    forever = end is None
    index = 0
    while forever or result < end:
        yield result
        index += 1
        result = begin + step * index

import itertools 


# 注意，下面示例中的 aritprog_gen 不是生成器函數(shù)，
# 因?yàn)槎x體中沒(méi)有 yield 關(guān)鍵字。
# 但是它會(huì)返回一個(gè)生成器，
# 因此它與其他生成器函數(shù)一樣，
# 也是生成器工廠函數(shù)。
def aritprog_two_gen(begin, step, end=None):
    first = type(begin + step)(begin)
    ap_gen = itertools.count(first, step)
    if end is not None:
        ap_gen = itertools.takewhile(lambda n: n < end, ap_gen)
    return ap_gen