Python3 hasattr()、getattr()、setattr()、delattr()函数

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

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

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()