python 堆栈

In our previous tutorial we learned about Python signal processing. In this tutorial we will learn about python stack.

在上一教程中，我们了解了Python信号处理 。 在本教程中，我们将学习python堆栈。

Python堆栈 (Python Stack)

To start with this tutorial, you have to know what is stack at first. Basically stack is Last-In-First-Out data structure. That means, the item that entered last in the system will be removed at first.

要开始本教程，您首先必须知道什么是堆栈。 基本上，堆栈是后进先出数据结构。 这意味着，系统中最后输入的项目将首先被删除。

For example, let’s say you have a pipe with only one open end. And you have some balls that fit just fine in the pipe. So when you will insert these balls in the pipe, they will get stacked on top of each other. However when you will remove the balls, the last one will be removed first.

例如，假设您的管道只有一个开口端。 而且您有一些球恰好适合管道。 因此，当您将这些球插入管道时，它们会相互堆叠。 但是，当您将球卸下时，最后一个将被首先卸下。

Python Stack推送 (Python Stack push)

Well, there is no additional data structure as python stack. But as stack is a very common data structure, we will try to implement that.

好吧，没有像python堆栈那样的其他数据结构。 但是由于堆栈是非常常见的数据结构，因此我们将尝试实现该结构。

So if you have already studied about stack, you should know that stack has two operations. One is push and another is pop. In this section we will be discussing about push operation. Push operation is used to add items to the stack. As we will be using Python List as stack, we can use append() function to push items into the list.

因此，如果您已经学习过堆栈，则应该知道堆栈有两个操作。 一个是push ，另一个是pop 。 在本节中，我们将讨论推入操作。 推送操作用于将项目添加到堆栈中。 因为我们将使用Python List作为堆栈，所以我们可以使用append()函数将项目推入列表中。

stack = []  # initialize a list as stack
print('current stack :', stack)# add items to the stack
for i in range(5):# push items into stackstack.append(i)print('current stack :', stack,'\tstack size :', len(stack))

The output of above stack implementation example will be like below image.

上面的堆栈实现示例的输出将如下图所示。

Python堆栈弹出 (Python Stack pop)

Now we need to learn how to pop items from stack. Python List has a function named pop() that removes the last element from the list. But before removing you have to check if the stack is empty. So, if we add pop implementation to the previous code, then the final code will be like below.

现在我们需要学习如何从堆栈中弹出项目。 Python列表具有一个名为pop()的函数，该函数从列表中删除最后一个元素。 但是在删除之前，您必须检查堆栈是否为空。 因此，如果我们在先前的代码中添加pop实现，那么最终的代码将如下所示。

stack = []  # initialize a list as stack
print('\ncurrent stack :', stack)print('\nPush items to the stack')
# add items to the stack
for i in range(5):# push items into stackstack.append(i)print('current stack :', stack,'\tstack size :', len(stack))print('\nPop items from te stack')
# now pop items from the stack
while len(stack) > 0:  # check if the stack is emptystack.pop()print('current stack :', stack, '\tstack size :', len(stack))

So, the output will be as like below.

因此，输出将如下所示。

Push items to the stack
current stack : [0]     stack size : 1
current stack : [0, 1]     stack size : 2
current stack : [0, 1, 2]     stack size : 3
current stack : [0, 1, 2, 3]     stack size : 4
current stack : [0, 1, 2, 3, 4]     stack size : 5Pop items from te stack
current stack : [0, 1, 2, 3]     stack size : 4
current stack : [0, 1, 2]     stack size : 3
current stack : [0, 1]     stack size : 2
current stack : [0]     stack size : 1
current stack : []     stack size : 0

Python Stack实施 (Python Stack implementation)

As you see that we can utilize List append() and pop() functions to create our Stack implementation class. Here is a Stack implementation class with example.

如您所见，我们可以利用List append（）和pop（）函数创建我们的Stack实现类。 这是一个带有示例的Stack实现类。

class Stack:stack = []  # empty listmax_size = -1def __init__(self, size=-1):  # defining maximum size in the constructorself.max_size = sizedef push(self, item):if self.max_size == -1:  # if there is no limit in stackself.stack.append(item)elif len(self.stack) < self.max_size:  # if max limit not crossedself.stack.append(item)else:  # if max limit crossedprint('Can\'t add item. Stack limit is :', self.max_size)raise RuntimeErrordef pop(self):if len(self.stack) > 0:temp = self.stack[-1]self.stack.pop()return tempelse:print('stack is already empty.')raise IndexErrordef top(self):if len(self.stack) > 0:return self.stack[-1]  # returns the last itemelse:print('stack is already empty.')raise IndexErrorstack = Stack()
stack.push(1)  # push item 1
stack.push(2)  # push item 2
print('Pop the last item :', stack.pop())  # pop the top item
print('Current top item is :', stack.top())  # current top item

The above code will output like this

上面的代码将这样输出

Pop the last item : 2
Current top item is : 1

So, that’s all about python stack. If you have any confusion regarding python stack implementation, please use the comment box.

所以，这一切都与python堆栈有关。 如果您对python堆栈的实现有任何疑问，请使用注释框。

Reference: Official Guide

参考： 官方指南

翻译自: https://www.journaldev.com/16045/python-stack

python 堆栈