# 数组有一个固定的长度。头指针和尾指针，都指向数组第一个值。# 当进行push操作的时候，头指针后移。当进行pop操作的时候，尾指针向后移# 当到达最后一个值的时候，重新指向第一个值。取模 %queue_size()# 首先实现一个数组class Array(object):    def __init__(self,size = 32):        self._size = size        self._items = [None] * size  # 容器_items, 是一个每个值为None的列表    def __getitem__(self, index):      # 实现下标访问        return self._items[index]    def __setitem__(self, index, value):        self._items[index] = value    def __len__(self):        return self._size    def clear(self, value=None):        for i in range(len(self._items)):            self._items[i] = value    def __iter__(self):        for item in self._items:            yield itemclass ArrayQueue(object):    def __init__(self, maxsize):        self.maxsize = maxsize        self.array = Array(maxsize)        self.head = 0        self.tail = 0    def push(self, value):        if len(self) >= self.maxsize:            raise Exception('queue full')        self.array[self.head % self.maxsize] = value        self.head += 1    def pop(self):        value = self.array[self.tail % self.maxsize]        self.tail += 1        return value    def __len__(self):        return self.head - self.taildef test_arrrayqueue():    import pytest    size = 5    q = ArrayQueue(size)    for i in range(size):        q.push(i)    assert len(q) == size    assert q.pop() == 0    assert q.pop() == 1    q.push(5)    assert len(q) == 4    assert q.pop() == 2    assert q.pop() == 3    assert q.pop() == 4    assert q.pop() == 5    assert len(q) == 0