Python 学习入门（37）—— @classmethod函数

@classmethod : 类方法

@staticmethod : 静态方法

类方法和静态方法的调用一样，都是通过类就可以直接调用。

区别：类方法，需要传入该类，定义类方法的时候要传一个默认的参数cls。静态方法则不用。

示例：

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# blog.ithomer.net

class test(object):
    x = 11
    def __init__(self, _x):
        self._x = _x
        print("test.__init__")
 
    @classmethod
    def class_method(cls):
        print("class_method")
 
    @staticmethod
    def static_method():
        print("static_method")
 
    @classmethod
    def getpt(cls):
        cls.class_method()
        cls.static_method()
 
if "__main__" == __name__:
    test.class_method()         # class_method
    test.static_method()        # static_method
    test.getpt()                # class_method  static_method

    t = test(22)                # test.__init__
    t.class_method()            # class_method
    t.static_method()           # static_method
    
    print test.x                # 11
#     print test._x
    
    print t.x                   # 11
    print t._x                  # 22
    
#     t.getpr()   # 'test' object has no attribute 'getpr'

运行结果：

class_method
static_method
class_method
static_method
test.__init__
class_method
static_method
11
11
22
traceback (most recent call last):
  file "/home/homer/workspace/mypython/com/connmiliao.py", line 40, in 
    t.getpr() 
attributeerror: 'test' object has no attribute 'getpr'

示例：@property,@staticmethod,@classmethod

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# blog.ithomer.net

class myclass(object):
    def __init__(self):
        print '__init__'
        self._name = 'blog.ithomer.net'

    @staticmethod
    def static_method():
        print 'this is a static method!'

    def test(self):
        print 'call test'

    @classmethod
    def class_method(cls):
        print 'cls: ',cls
        print 'cls.name: ',cls.name
        print 'cls.static_method(): ',cls.static_method()
        instance = cls()
        print 'instance.test(): ',instance.test()

    @property
    def name(self):
        return self._name
    
    @name.setter
    def name(self, value):
        self._name = value

if __name__ == '__main__':
    myclass.static_method()
    myclass.class_method()
    
    mc = myclass()
    print mc.name
    mc.name = 'forum.ithomer.net'  
    print mc.name

运行结果：

this is a static method!
cls:
cls.name:
cls.static_method(): this is a static method!
none
__init__
instance.test(): call test
none
__init__
blog.ithomer.net
forum.ithomer.net