python __str__ & __repr__ & __cmp__

For ( __str__ ),we going to see a example ...

and find who is working for ...

#!/usr/bin/python

class Person(object):

    def __init__(self,name,gender):
        self.name = name
        self.gender = gender

if __name__ == '__main__':

    p = Person('Frank',23)
    print p

See,The instance of ( Person ) have a default method ,just like ( describe method ) ...

it's called by instance self (here,is p itself) ...

So,what it is name ...

keep read,you will find what's it is ...

#!/usr/bin/python

class Person(object):

    def __init__(self,name,gender):
        self.name = name
        self.gender = gender

    def __str__(self):
    　　 """override the object method"""
        return 'Person object: %s,%d' % (self.name,self.gender)

if __name__ == '__main__':

    p = Person('Frank',23)
    print p

See,we got a totally different result ...

So,we know who is the method ( __str__ ) ...

Okay,next we will talk (__cmp__) inside method ...

#!/usr/bin/python

class Student(object):

    def __init__(self,name,score):
        self.name = name
        self.score = score

    def __str__(self):
        return '(%s: %s)' % (self.name,self.score)

    __repr__ = __str__

    def __cmp__(self,s):
        if self.score > s.score:
            return -1

        elif self.score < s.score:
            return 1

        else:
            if self.name < s.score:
                return -1
            elif self.name < s.name:
                return 1
            else:
                return 0

if __name__ == '__main__':
    L = [Student('Tim',99),Student('Bob',88),Student('Alice',99)]
    print sorted(L)