1.什么是双端队列
deque的英文意思是Double-Ended Queue,deque是为了在两端高效实现插入和删除操作的双向列表,适合用于队列和栈:deque除了实现list的append()和pop()外,还支持appendleft()和popleft(),这样就可以非常高效地往头部或者尾部添加或删除元素
与常见的list使用区别如下所示
常用的接口
deque:append和popleft
(1)deque接收GIL管理,线程安全。list没有GIL锁,所以线程不安全。也就是说,在并发场景中,list可能会导致一致性问题,而deque不会。
(2)deque支持固定长度。当长度满了,当我们继续使用append时,它会自动弹出最早插入的数据。
(3) deque 更快
See the following code example of Deque in Python.
#importing deque from collections module from collections import deque #initializing the deque object deq = deque(['apple', 'mango', 'orange']) #printing the initial deque object print("Printing the initial deque object items \n" , deq, '\n') #append(x) demonstration print("Appending a new element to the right of deque") deq.append('papaya') print(deq , '\n') #appendleft(x) demonstration print("Appending a new element to the left of deque") deq.appendleft('strawberry') print(deq , '\n') #count(x) demonstration print("Counting the the occurrence of apple in deque") print(deq.count('apple') , '\n') #extend(iterable) demonstration deq.extend(['grapes', 'watermelon']) print("Extending the deque with new items on the right") print(deq, "\n") extendleft(iterable) demonstration deq.extendleft(['pear', 'guava']) print("Extending the deque with new items on the left") print(deq, "\n") #index(x [, start [, stop]]) demonstration print("Finding the index of an item") print(deq.index('strawberry'), "\n") #insert(i,x) demonstration print("Inserting an item to the deque by specifiying the index") deq.insert(2,'banana') print(deq, "\n") #pop() demonstration print("Popping out last item from the right") print(deq.pop(), "\n") #popleft() demonstration print("Popping out first item from the left") print(deq.popleft(), "\n") #remove() demonstration print("Removing an item from the deque") deq.remove("apple") print(deq, "\n")
运行结果:
Printing the initial deque object items deque(['apple', 'mango', 'orange']) Appending a new element to the right of deque deque(['apple', 'mango', 'orange', 'papaya']) Appending a new element to the left of deque deque(['strawberry', 'apple', 'mango', 'orange', 'papaya']) Counting the the occurrence of apple in deque 1 Extending the deque with new items on the right deque(['strawberry', 'apple', 'mango', 'orange', 'papaya', 'grapes', 'watermelon']) Extending the deque with new items on the left deque(['guava', 'pear', 'strawberry', 'apple', 'mango', 'orange', 'papaya', 'grapes', 'watermelon']) Finding the index of an item 2 Inserting an item to the deque by specifiying the index deque(['guava', 'pear', 'banana', 'strawberry', 'apple', 'mango', 'orange', 'papaya', 'grapes', 'watermelon']) Popping out last item from the right watermelon Popping out first item from the left guava Removing an item from the deque deque(['pear', 'banana', 'strawberry', 'mango', 'orange', 'papaya', 'grapes'])
如果需要使用一个容器来处理数据 请使用deque