数据结构（三）：队列

 1 from array import array
 2 
 3 class arr_queue(object):
 4     def __init__(self, maxsize):
 5         self._array = array(‘i‘, range(maxsize))
 6         self._head = 0
 7         self._tail = 0
 8         self._length = 0
 9         self._maxsize = maxsize
10 
11     def enqueue(self, value):
12         if self._length >= self._maxsize:
13             raise Exception(‘queue is full‘)
14         self._array[self._tail] = value
15         self._length += 1
16         self._tail += 1
17         if self._tail >= self._maxsize:
18             self._tail = 0
19 
20     def dequeue(self):
21         if self._length <= 0:
22             raise Exception(‘queue is empty‘)
23         value = self._array[self._head]
24         self._length -= 1
25         self._head += 1
26         if self._head >= self._maxsize:
27             self._head = 0
28         return value
29 
30     def __len__(self):
31         return self._length