理解python：@classmethod 和@staticmethod

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具体详情，请看参考链接！

用途：

写与类进行交互的方法，而不是实例。

@classmethod:

使用地方：
和类进行交互，但不和其实例进行交互的函数方法

举个例子：

在类外定义一个函数，来与类进行交互[坏处：扩散类代码的关系到类定义外]

class ClassandStaticMethod(object):    value = "get the value without instance"    def __init__(self,data):        self.data = datadef InteractClassWithoutInstance(cls):    return cls.value+" added successfuly"print InteractClassWithoutInstance(ClassandStaticMethod)#result>get the value without instanceadded successfuly

使用@classmethod的方式：

class ClassandStaticMethod(object):    value = "get the value without instance"    def __init__(self,data):        self.data = data    @classmethod    def InteractClassWithoutInstance(cls):        return cls.value+" added successfuly"print ClassandStaticMethod.InteractClassWithoutInstance()#instance #也可以实例化之后使用该函数。cs = ClassandStaticMethod("Jack")print cs.InteractClassWithoutInstance()#result> get the value without instance added successfuly  get the value without instance added successfuly

@staticmethod:

使用地方：
有一些和类相关函数，但不要使用该类或者该类的实例；比如更改环境变量或者修改其他类的属性等。

class ClassandStaticMethod(object):    value = "get the value without instance"    def __init__(self,data):        self.data = data    @classmethod    def InteractClassWithoutInstance(cls):        return cls.value+" added classmethod successfuly"    @staticmethod    def set_variable(value):        return value+" added  successfuly "print ClassandStaticMethod.InteractClassWithoutInstance()print ClassandStaticMethod.set_variable("staticmethod")#instance cs = ClassandStaticMethod("Jack")print cs.InteractClassWithoutInstance()print cs.set_variable("staticmethod_2")#result>get the value without instance added classmethod successfulystaticmethod added  successfuly get the value without instance added classmethod successfulystaticmethod_2 added  successfuly

示例二：

class Kls(object):    def __init__(self, data):        self.data = data    def printd(self):        print(self.data)    @staticmethod    def smethod(*arg):        print('Static:', arg)    @classmethod    def cmethod(*arg):        print('Class:', arg)Kls.smethod(1,2,4)Kls.cmethod(1,2,5)ik = Kls(123)ik.smethod(1,2,4)ik.cmethod(1,2,5)#result>('Static:', (1, 2, 4))('Class:', (<class '__main__.Kls'>, 1, 2, 5))('Static:', (1, 2, 4))('Class:', (<class '__main__.Kls'>, 1, 2, 5))

notice: classmethod需要一个对类的引用作为第一个参数，而staticmethod不需要。

ref:

http://stackoverflow.com/questions/12179271/python-classmethod-and-staticmethod-for-beginner
http://pythoncentral.io/difference-between-staticmethod-and-classmethod-in-python/

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