两队列模拟一个栈，python实现

python实现两个队列模拟一个栈：

class Queue(object):

    def __init__(self):

        self.stack1=[]

        self.stack2=[]

    def enqueue(self, item):

        if len(self.stack1) == 0:

            self.stack1.append(item)

        elif len(self.stack2) == 0:

            self.stack2.append(item)

        if len(self.stack2)==1 and len(self.stack2) >= 1:

            while len(self.stack1)>0:

                self.stack2.append(self.stack1.pop(0))

        elif len(self.stack1)==1 and len(self.stack2) >= 1:

            while len(self.stack2)>0:

                self.stack1.append(self.stack2.pop(0))

    def dequeue(self):

        if self.stack1:

            return self.stack1.pop(0)

        elif self.stack2:

            return self.stack2.pop(0)

        else:

            return None

q = Queue()

q.enqueue(3)

# print(q.dequeue())

q.enqueue(4)

q.enqueue(5)

q.enqueue(6)

print(q.dequeue())

print(q.dequeue())

print(q.dequeue())

print(q.dequeue())