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

hasattr()函數

　　hasattr()函數用於判斷是否包含對應的屬性

語法：

　　hasattr(object,name)

參數：

　　object--對象

　　name--字符串，屬性名

返回值：

　　如果對象有該屬性返回True，否則返回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()函數

描述：

　　getattr()函數用於返回一個對象屬性值

語法：

　　getattr(object,name,default)

參數：

　　object--對象

　　name--字符串，對象屬性

　　default--默認返回值，如果不提供該參數，在沒有對於屬性時，將觸發AttributeError。

返回值：

　　返回對象屬性值

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)
#報錯
# File "/getattr()函數.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()函數

描述：

　　setattr函數，用於設置屬性值，該屬性必須存在

語法：

　　setattr(object,name,value)

 參數：

　　object--對象

　　name--字符串，對象屬性

　　value--屬性值

返回值：

　　無

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) #等同於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()函數

描述：

　　delattr函數用於刪除屬性

　　delattr(x,'foobar)相當於del x.foobar

語法：

　　setattr(object,name)

參數：

　　object--對象

　　name--必須是對象的屬性

返回值：

　　無

 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') #等同於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}

補充示例：

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()