どうやってスタックを実現しますか

"""
          ，        ：  ，  ，     ，       ，           。
"""


#    ：    
class MyStack1:
    #    
    def __init__(self):
        self.items = []

    #        
    def isEmpty(self):
        return len(self.items) == 0

    #       
    def size(self):
        return len(self.items)

    #        
    def top(self):
        if not self.isEmpty():
            return self.items[len(self.items) - 1]
        else:
            return None

    #   
    def pop(self):
        if not self.isEmpty():
            return self.items.pop()
        else:
            print('     ')
            return None

    #   
    def push(self, item):
        self.items.append(item)


#    ：    
class LNode:
    def __int__(self):
        self.data = None
        self.next = None


class MyStack2:
    def __init__(self):
        self.data = None
        self.next = None

    #   stack    ，      true，    else
    def empty(self):
        if self.next is None:
            return True
        else:
            return False

    #          
    def size(self):
        size = 0
        p = self.next
        while p is not None:
            p = p.next
            size += 1
        return size

    #   ： e    
    def push(self, e):
        p = LNode()
        p.data = e
        p.next = self.next
        self.next = p

    #   ：        
    def pop(self):
        tmp = self.next
        if tmp is not None:
            self.next = tmp.next
            return tmp.data
        print('    ')
        return None

    #       
    def top(self):
        if self.next is not None:
            return self.next.data
        print('    ')
        return None


if __name__ == '__main__':
    s = MyStack1()
    s.push(4)
    print('     ：' + str(s.top()))
    print('    ：' + str(s.size()))
    s.pop()
    print('    ')
    s.pop()

    stack = MyStack2()
    stack.push(1)
    print('     ：' + str(stack.top()))
    print('    ：' + str(stack.size()))
    stack.pop()
    print('    ')
    stack.pop()