编程实现循环队列的入队列，计算该队列长度，然后出队列

以下是Python代码实现：

class CircularQueue:
    def __init__(self, size):
        self.size = size
        self.queue = [None] * size
        self.front = self.rear = -1

    def is_empty(self):
        return self.front == -1

    def is_full(self):
        return (self.rear + 1) % self.size == self.front

    def enqueue(self, item):
        if self.is_full():
            print("Queue is full!")
        elif self.is_empty():
            self.front = self.rear = 0
            self.queue[self.rear] = item
        else:
            self.rear = (self.rear + 1) % self.size
            self.queue[self.rear] = item

    def dequeue(self):
        if self.is_empty():
            print("Queue is empty!")
        elif self.front == self.rear:
            item = self.queue[self.front]
            self.front = self.rear = -1
            return item
        else:
            item = self.queue[self.front]
            self.front = (self.front + 1) % self.size
            return item

    def length(self):
        if self.is_empty():
            return 0
        elif self.front <= self.rear:
            return self.rear - self.front + 1
        else:
            return self.size - self.front + self.rear + 1


# Test the implementation
cq = CircularQueue(5)

cq.enqueue(1)
cq.enqueue(2)
cq.enqueue(3)
cq.enqueue(4)
cq.enqueue(5)

print("Length of queue:", cq.length())

print("Dequeued items:")
print(cq.dequeue())
print(cq.dequeue())
print(cq.dequeue())

print("Length of queue:", cq.length())

输出结果：

Length of queue: 5
Dequeued items:
1
2
3
Length of queue: 2