Python实现一个简单的栈结构

基于list来实现一个栈：

class SimpleStack:
    def __init__(self):
        self.__stack: list = []
​
    def __iter__(self):
        return SimpleStackIterator(self)
​
    def __len__(self):
        return len(self.__stack)
​
    def __getitem__(self, index):
        if index >= len(self.__stack):
            return None
        return self.__stack[index]
​
    def pop(self):
        if len(self.__stack) <= 0:
            return None
        return self.__stack.pop()
​
    def push(self, item):
        return self.__stack.append(item)

定义一个栈的迭代器，实现对栈进行迭代，但不弹出栈中的元素

class SimpleStackIterator:
    def __init__(self, iterable: SimpleStack):
        self.__iterable = iterable
        self.__len = len(iterable)
        self.__current = 0
​
    def __iter__(self):
        return self
​
    def __next__(self):
        while True:
            if self.__current >= self.__len:
                raise StopIteration
            ele = self.__iterable[self.__current]
            self.__current += 1
            return ele

具体使用：

stack_size = 5
stack = SimpleStack()
​
for i in range(stack_size):
    stack.push(i)
​
for i in iter(stack):
    print(i)
​
for i in range(stack_size):
    ele = stack.pop()
    print(ele)