python什么时候用类方法

class Kls(object):
 num_inst = 0

 def __init__(self):
 Kls.num_inst = Kls.num_inst + 1

 @classmethod
 def get_no_of_instance(cls):
 return cls.num_inst


ik1 = Kls()
ik2 = Kls()

print ik1.get_no_of_instance()
print Kls.get_no_of_instance()

coding:utf-8
class Book(object):
def __init__(self, title):
self.title = title
 @classmethod
def class_method_create(cls, title):
book = cls(title=title)
return book
 @staticmethod
def static_method_create(title):
book= Book(title)
return book
book1 = Book("use instance_method_create book instance")
book2 = Book.class_method_create("use class_method_create book instance")
book3 = Book.static_method_create("use static_method_create book instance")
print(book1.title)
print(book2.title)
print(book3.title)