python实现一个Stack类

# -*- coding:utf-8 -*-
class Stack(object):
    """
        Stack 类
    """
    def __init__(self, other=None):
        """doc test
        >>> s = Stack([1,2,3,4])
        >>> s.pop()
        4
        >>> s.count
        3
        >>> e = Stack([1,2,3,4])
        >>> s != e
        True
        >>> s.push(4)
        >>> s == e
        True
        >>> s += e
        >>> len(s)
        8
        >>> s.clear()
        >>> s.empty
        True
        >>> s.top
        data is empty
        """
        self.data = []
        if other is not None:
            if isinstance(other, Stack):
                self.data[:] = other.data
            elif isinstance(other, (list, tuple, set)):
                self.data[:] = list(other)
            else:
                self.data  = list(other)

    def __repr__(self):
        return "<Stack: %s>" % str(self.data)

    def __len__(self):
        return len(self.data)

    def __eq__(self, other):
        return self.data == self.__cast(other)

    def __getitem__(self, i):
        return self.data[i]

    def __setitem__(self, i, item):
        self.data[i] = item

    def __delitem__(self, i):
        del self.data[i]

    def __add__(self, other):
        if isinstance(other, Stack):
            return self.__class__(self.data + other.data)
        else:
            raise TypeError('unsupported operand type(s) for +: %s' %(getattr(other,"__class__",'')))

    def __iadd__(self, other):
        if isinstance(other, Stack):
            self.data += other.data
            return self
        else:
            raise TypeError('unsupported operand type(s) for +=: %s' %(getattr(other,"__class__",'')))

    def __cast(self, other):
        if isinstance(other, Stack):
            return other.data
        else:
            return other

    @property
    def top(self):
        if self.empty:
            print 'data is empty'
            return None
        return self.data[-1]

    @property
    def count(self):
        return len(self.data)

    @property
    def empty(self):
        return len(self.data) == 0

    def push(self, item):
        self.data.append(item)

    def pop(self):
        if self.empty:
            print 'data is empty'
            return None
        return self.data.pop()

    def clear(self):
        self.data = []