编写程序实现顺序栈的初始化、判断栈空否、入栈和出栈

以下是Python语言的实现：

class Stack:
    def __init__(self, capacity):
        self.capacity = capacity     # 栈的容量
        self.top = -1                # 栈顶的索引
        self.data = [None] * capacity   # 存储数据的数组

    def is_empty(self):
        return self.top == -1

    def push(self, value):
        if self.top == self.capacity - 1:
            print("Stack Overflow")
            return
        self.top += 1
        self.data[self.top] = value

    def pop(self):
        if self.is_empty():
            print("Stack Underflow")
            return None
        value = self.data[self.top]
        self.top -= 1
        return value

测试代码：

stack = Stack(5)
print(stack.is_empty())  # True

stack.push(1)
stack.push(2)
stack.push(3)
print(stack.pop())  # 3

stack.push(4)
stack.push(5)
stack.push(6)  # Stack Overflow

print(stack.pop())  # 5
print(stack.pop())  # 4
print(stack.pop())  # 2
print(stack.pop())  # 1
print(stack.pop())  # Stack Underflow