python3 hasattr getattr setattr delattr 对象属性反射

短命女 2021-07-28 13:56 287阅读 0赞

# hasattr()函数 #

hasattr()函数用于判断是否包含对应的属性

语法：

hasattr(object,name)

参数：

object--对象

name--字符串，属性名

返回值：

如果对象有该属性返回True，否则返回False

示例：

class People:
        country='China'
        def __init__(self,name):
            self.name=name
    
        def people_info(self):
            print('%s is xxx' %(self.name))
    
    obj=People('aaa')
    
    print(hasattr(People,'country'))
    #返回值：True
    print('country' in People.__dict__)
    #返回值：True
    print(hasattr(obj,'people_info'))
    #返回值：True
    print(People.__dict__)
    ##{'__module__': '__main__', 'country': 'China', '__init__': <function People.__init__ at 0x1006d5620>, 'people_info': <function People.people_info at 0x10205d1e0>, '__dict__': <attribute '__dict__' of 'People' objects>, '__weakref__': <attribute '__weakref__' of 'People' objects>, '__doc__': None}

#  getattr()函数 #

描述：

getattr()函数用于返回一个对象属性值

语法：

getattr(object,name,default)

参数：

object--对象

name--字符串，对象属性

default--默认返回值，如果不提供该参数，在没有对于属性时，将触发AttributeError。

返回值：

返回对象属性值

示例：

class People:
        country='China'
        def __init__(self,name):
            self.name=name
    
        def people_info(self):
            print('%s is xxx' %(self.name))
    
    obj=getattr(People,'country')
    print(obj)
    #返回值China
    #obj=getattr(People,'countryaaaaaa')
    #print(obj)
    #报错
    # File "/getattr()函数.py", line 32, in <module>
    #     obj=getattr(People,'countryaaaaaa')
    # AttributeError: type object 'People' has no attribute 'countryaaaaaa'
    obj=getattr(People,'countryaaaaaa',None)
    print(obj)
    #返回值None

# setattr()函数 #

描述：

setattr函数，用于设置属性值，该属性必须存在

语法：

setattr(object,name,value)

参数：

object--对象

name--字符串，对象属性

value--属性值

返回值：

无

示例：

class People:
        country='China'
        def __init__(self,name):
            self.name=name
    
        def people_info(self):
            print('%s is xxx' %(self.name))
    
    obj=People('aaa')
    
    setattr(People,'x',111) #等同于People.x=111
    print(People.x)
    
    #obj.age=18
    setattr(obj,'age',18)
    print(obj.__dict__)
    #{'name': 'aaa', 'age': 18}
    print(People.__dict__)
    #{'__module__': '__main__', 'country': 'China', '__init__': <function People.__init__ at 0x1007d5620>, 'people_info': <function People.people_info at 0x10215d1e0>, '__dict__': <attribute '__dict__' of 'People' objects>, '__weakref__': <attribute '__weakref__' of 'People' objects>, '__doc__': None, 'x': 111}

# delattr()函数 #

描述：

delattr函数用于删除属性

delattr(x,'foobar)相当于del x.foobar

语法：

setattr(object,name)

参数：

object--对象

name--必须是对象的属性

返回值：

无

示例：

class People:
        country='China'
        def __init__(self,name):
            self.name=name
    
        def people_info(self):
            print('%s is xxx' %(self.name))
    
    delattr(People,'country') #等同于del People.country
    print(People.__dict__)
    {'__module__': '__main__', '__init__': <function People.__init__ at 0x1006d5620>, 'people_info': <function People.people_info at 0x10073d1e0>, '__dict__': <attribute '__dict__' of 'People' objects>, '__weakref__': <attribute '__weakref__' of 'People' objects>, '__doc__': None}

## 补充示例： ##

class Foo:
        def run(self):
            while True:
                cmd=input('cmd>>: ').strip()
                if hasattr(self,cmd):
                    func=getattr(self,cmd)
                    func()
    
        def download(self):
            print('download....')
    
        def upload(self):
            print('upload...')
    
    # obj=Foo()
    # obj.run()