Python3 中hasattr()、getattr()、setattr()、delattr()函数及示例代码数
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
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=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：
'''
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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))
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()
