Python内置函数(60)——staticmethod

英文文档:

staticmethod(function)

Return a static method for function.

A static method does not receive an implicit first argument.

The @staticmethod form is a function decorator – see the description of function definitions in Function definitions for details.

It can be called either on the class (such as C.f()) or on an instance (such as C().f()). The instance is ignored except for its class.

 

说明:

  1. 类中普通的方法,实际上既可以被类直接调用也可以被类的实例对象调用,但是被实例对象调用的时候,要求方法至少有一个参数,而且调用时会将实例对象本身传给第一个参数。

>>> class Student(object):
    def __init__(self,name):
        self.name = name
    def sayHello(lang):
        print(lang)
        if lang == 'en':
            print('Welcome!')
        else:
            print('你好!')
  
    
>>> Student.sayHello
<function Student.sayHello at 0x02AC7810>
>>> a = Student('Bob')
>>> a.sayHello
<bound method Student.sayHello of <__main__.Student object at 0x02AD03F0>>

>>> Student.sayHello('en') # 类调用的时候,将'en'传给了lang参数
en
Welcome!

>>> a.sayHello() # 类实例对象调用的时候,将对象本身自动传给了lang参数,不能再接收参数
<__main__.Student object at 0x02AD03F0>
你好!

  >>> a.sayHello('en')
  Traceback (most recent call last):
  File "<pyshell#7>", line 1, in <module>
  a.sayHello('en')
  TypeError: sayHello() takes 1 positional argument but 2 were given

 

  

  2. staticmethod函数功能就是将一个方法定义成类的静态方法,正确的方法是使用 @staticmethod装饰器,这样在实例对象调用的时候,不会把实例对象本身传入静态方法的第一个参数了。

# 使用装饰器定义静态方法
>>> class Student(object):
    def __init__(self,name):
        self.name = name
    @staticmethod
    def sayHello(lang):
        print(lang)
        if lang == 'en':
            print('Welcome!')
        else:
            print('你好!')

            
>>> Student.sayHello('en') #类调用,'en'传给了lang参数
en
Welcome!

>>> b = Student('Kim') #类实例对象调用,不再将类实例对象传入静态方法
>>> b.sayHello()
Traceback (most recent call last):
  File "<pyshell#71>", line 1, in <module>
    b.sayHello()
TypeError: sayHello() missing 1 required positional argument: 'lang'

>>> b.sayHello('zh')  #类实例对象调用,'zh'传给了lang参数
zh
你好!

 

posted @ 2016-11-16 13:21  十月狐狸  阅读(1635)  评论(0编辑  收藏  举报