一、isinstance(obj,cls)和issubclass(sub,super)
1.1、isinstance(obj,cls)
isinstance(obj,cls)检查是否obj是否是类 cls 的对象
class Foo(object):
pass
obj = Foo()
print(isinstance(obj,Foo)) #True
1.2、issubclass(sub, super)
issubclass(sub, super)检查sub类是否是 super 类的派生类
class Foo(object):
pass
class Bar(Foo):
pass
print(issubclass(Bar,Foo)) #True
二、反射
四个可以实现自省的函数，适用于类和对象（一切皆对象，类本身也是一个对象）
2.1、hasattr(object,name)
判断object中有没有一个name字符串对应的方法或属性
2.2、getattr(object, name, default=None)
def getattr(object, name, default=None): # known special case of getattr
"""
getattr(object, name[, default]) -> value
Get a named attribute from an object; getattr(x, 'y') is equivalent to x.y.
When a default argument is given, it is returned when the attribute doesn't
exist; without it, an exception is raised in that case.
"""
pass
getattr(object, name, default=None)
2.3、setattr(x, y, v)
设置属性
def setattr(x, y, v): # real signature unknown; restored from __doc__
"""
Sets the named attribute on the given object to the specified value.
setattr(x, 'y', v) is equivalent to ``x.y = v''
"""
pass
setattr(x, y, v)
2.4、delattr(x, y)
删除属性
def delattr(x, y): # real signature unknown; restored from __doc__
"""
Deletes the named attribute from the given object.
delattr(x, 'y') is equivalent to ``del x.y''
"""
pass
delattr(x, y)
2.5、示例
1）示例一
class BlackMedium:
feature = "Ugly"
def __init__(self,name,addr):
self.name = name
self.addr = addr
def sell_house(self):
print("%s 黑中介卖房子啦" %self.name)
def rent_house(self):
print("%s 黑中介租房子啦" %self.name)
b1 = BlackMedium("万成置地","天露园")
#检测是否含有某属性
print(hasattr(b1,"name")) #True
print(hasattr(b1,"sell_house")) #以字符串的形式，否则NameError: name 'sell_house' is not defined
#print(hasattr(b1,rent_house)) #NameError: name 'sell_house' is not defined
#获取属性
print(getattr(b1,"name")) #万成置地 ==>获取数据属性
func = getattr(b1,"rent_house") #获取函数属性
func() #万成置地 黑中介租房子啦
# getattr(b1,"abc") #当属性不存在时报错AttributeError: 'BlackMedium' object has no attribute 'abc'
print(getattr(b1,"abc","不存在")) #不存在 ==>当使用getattr获取属性时，当属性不存在，可以指定默认返回值
#设置属性
setattr(b1,"sb","True") #设置数据属性
print(b1.__dict__) #{'name': '万成置地', 'addr': '天露园', 'sb': 'True'}
setattr(b1,"show_name",lambda self:self.name+"_sb") #设置函数属性
print(b1.__dict__) #{'sb': 'True', 'name': '万成置地', 'show_name': <function <lambda> at 0x000001B354757F28>, 'addr': '天露园'}
print(b1.show_name(b1)) #万成置地_sb
#删除属性
print(b1.__dict__) #{'name': '万成置地', 'sb': 'True', 'addr': '天露园', 'show_name': <function <lambda> at 0x0000029A9F8D7F28>}
delattr(b1,"addr")
delattr(b1,"show_name")
# delattr(b1,"show_name123") #AttributeError: show_name123 属性不存在时报错
print(b1.__dict__) #{'sb': 'True', 'name': '万成置地'}
2）示例二
class Foo(object):
staticField = "oldboy"
def __init__(self):
self.name = name
def func(self):
return "func"
@staticmethod
def bar():
return "bar"
print(getattr(Foo,"staticField")) #oldboy
print(getattr(Foo,"func")) #<function Foo.func at 0x00000237B782E378>
print(getattr(Foo,"bar")) #<function Foo.bar at 0x00000228D871E400>
3）示例三
查看自身模块
import sys
def s1():
print("s1")
def s2():
print("s2")
this_module = sys.modules[__name__]
print(this_module) #<module '__main__' from 'G:/python/反射.py'> ==> __main__表示当前模块
print(hasattr(this_module,"s1")) #True
print(getattr(this_module,"s2")) #<function s2 at 0x000001B74743E378>
4）示例四
导入其他模块，利用反射查看该模块是否存在某个方法
module_test.py:
def test():
print('from the test')
index.py:
import aaa.module_test as obj obj.test() #from the test print(obj) #<module 'aaa.module_test' from 'G:\\python\\aaa\\module_test.py'> print(hasattr(obj,'test')) #True print(getattr(obj,"test")) #<function test at 0x0000024770C3E400>返回函数地址 getattr(obj,'test')() #from the test