python魔法函数的一些疑问

看了魔法函数，有一点疑问。1中需要用self.word才能执行，而2直接用self就可以执行。而1中Word继承了int基本类型，但在__new__时并没有什么卵用。当用

Word(“123”)来实例化时，看到的运算结果是以字符串形式来进行运算的，比如“123”*3=123123123。

1.

class Word(int):
    def __new__(cls, word):
        word = int(word)
        return int.__new__(cls,word)
    def __init__(self,word):
        self.word = word

    def __add__(self, other):
        return self.word+other

    def __sub__(self,other):
        return self.word-other

    def __mul__(self, other):
        return self.word*other

    def __div__(self, other):
        return sself.word/other

def main():
    a=Word(123)
    b=Word(12)
    print a-b
if __name__ == '__main__':
    main()

2.

class Word(str):
    def __new__(cls, word):
        word = word.replace(" ","")
        return str.__new__(cls,word)

    def __init__(self,word):
        self.word = word

    def __gt__(self, other):
        return len(self)>len(other)

    def __lt__(self,other):
        return len(self)<len(other)

    def __ge__(self, other):
        return len(self)>=len(other)

    def __le__(self, other):
        return len(self)<=len(other)
    def __eq__(self, other):
        return len(self)==len(other)

def main():
    a=Word("foorrrdd")
    b=Word("sswwss")
    print a==b
if __name__ == '__main__':
    main()