环形队列Python实现，From http://blog.csdn.net/hjj414/article/details/37579317

queue.py

class queue:  
    def __init__(self, capacity = 10):  
        '''
        capacity 队列大小
        '''
        self.capacity = capacity  
        self.size = 0  
        self.front = 0  
        self.rear = 0  
        self.array = [0]*capacity  
  
    def is_empty(self):  
        # 判断队列是否为空
        return 0 == self.size  
  
    def is_full(self):
        # 判断队列是否已满
        return self.size == self.capacity  
  
    def enqueue(self, element):  
        # 入队
        if self.is_full():  
            # 判断是否已满
            raise Exception('queue is full')  # 自定义错误信息
  
        self.array[self.rear] = element  
        self.size += 1  
        self.rear = (self.rear + 1) % self.capacity  
  
    def dequeue(self):  
        if self.is_empty():  
            # 判断队列是否为空
            raise Exception('queue is empty')  
  
        self.size -= 1  
        self.front = (self.front + 1) % self.capacity  # 更改队首位置
  
    def get_front(self):  
        # 获取队首
        return self.array[self.front]  
  
def main():  
    q = queue(3)  
  
    for i in range(3):  
        q.enqueue(i)  
    #q.enqueue(10)  
    q.dequeue()  
    q.dequeue()  
    q.enqueue(333)  
      
    while False == q.is_empty():  
        print q.get_front(),  
        q.dequeue()  
    #q.dequeue()  
  
if __name__ == '__main__':  
    main()