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)