用最大堆实现最大优先队列(Python)

'''
优先队列：优先队列是根据堆来实现的
最大优先队列根据最大堆实现
本程序以最大优先队列为例
堆是存放在数组中的，当元素数量超过数组长度时需要进行扩容
'''
class PrioriityQueue:
    def __init__(self):
        self.array=[]
        self.size=0

    def enqueue(self,element):
        self.array.append(element)
        self.size += 1
        self.up_adjust() # 调用类内函数，需要加self

    def dequeue(self):
        if self.size<0:
            raise Exception('队列为空')
        head=self.array[0]
        self.array[0]=self.array[self.size-1]
        self.array.pop() # 一定记得加上这一句，要不然原数组是不会变的
        self.size -= 1
        self.down_adjust()
        return head

    def up_adjust(self):
        child_index=self.size-1
        parent_index=(child_index-1)//2
        temp=self.array[child_index]
        while child_index>0 and temp>self.array[parent_index]:
            self.array[child_index]=self.array[parent_index]
            child_index=parent_index
            parent_index=(child_index-1)//2
        self.array[child_index]=temp

    def down_adjust(self):
        parent_index=0
        temp=self.array[parent_index]
        child_index=1
        while child_index<self.size:
            if child_index+1<self.size and self.array[child_index]<self.array[child_index+1]:
                child_index += 1
            if temp>self.array[child_index]:
                break
            self.array[parent_index]=self.array[child_index]
            parent_index=child_index
            child_index=2*parent_index+1
        self.array[parent_index]=temp

    def printList(self):
        print(self.array)

queue=PrioriityQueue()
queue.enqueue(3)
queue.enqueue(6)
queue.enqueue(2)
queue.enqueue(8)
queue.enqueue(4)
queue.printList()
print(queue.dequeue())
queue.printList()
print(queue.dequeue())
queue.printList()
queue.enqueue(1)
queue.printList()
print(queue.dequeue())
queue.printList()