迭代器如何等价于itertools.count在Python中实现而不使用生成器函数?

collections.abc.Iterator 用较少的代码实现计数

from collections.abc import Iterator

class count(Iterator):
    def __init__(self, start=0, step=1):
        self.c, self.step = start-step, step

    def __next__(self):
        self.c += self.step
        return self.c

unittest 这方面的框架。

下面是一个示例,其中包含几个在循环中使用类并检查迭代器值的测试:

import unittest
import random


class TestCount(unittest.TestCase):
    loops = 20

    def test_default(self):
        c = Count()
        for i in range(self.loops):
            self.assertEqual(i, next(c))

    def test_start(self):
        start = random.randint(-10, 10)
        c = Count(start=start)
        for i in range(start, start + self.loops):
            self.assertEqual(i, next(c))

    def test_step_pos(self):
        step = random.randint(1, 5)
        c = Count(step=step)
        for i in range(0, self.loops, step):
            self.assertEqual(i, next(c))

    def test_step_neg(self):
        step = random.randint(-5, -1)
        c = Count(step=step)
        for i in range(0, -self.loops, step):
            self.assertEqual(i, next(c))