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Python3 hasattr()、getattr()、setattr()、delattr()函数--编程学习网

发布时间:2018-04-18 08:48:52   来源:本站编辑   浏览次数:
  • 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:

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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}
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  •  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

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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
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  • 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:

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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}
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  • 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:

 示例:

复制代码
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}
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补充示例:

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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()

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