栈的顺序表实现

class Lstack():
    def __init__(self,top=-1,full=20):
        self._top = top
        self._stack=[]
        self.full = full
    def is__full(self):
        return self.full == self._top+1
    def is_empty(self):
        return self._top == -1
    def push(self,x):
        if self.full == self._top+1:
            print("堆栈已满")
        else:
            self._stack.append(x)
            self._top += 1
    def pop(self):
        if self._top == -1:
            print("堆栈为空，不可弹出")
        else:
            top =self._top
            self._top -= 1
            return self._stack.pop(top) # 这里一定要把top的元素弹出，而不是单纯的访