通过字符串的形式操作对象的相关属性。
方法有hasattr,getattr,delattr

#!/usr/bin/env python# -*- coding:utf-8 -*-# Author: vitaclass People: country='China' def __init__(self,name,age): self.name=name self.age=age def talk(self): print('%s is talking' %self.name)obj=People('egon',18)print(obj.name) #obj.__dict__['name']print(obj.talk)choice='name'# 这样直接使用字符串是不可以的，报错信息 AttributeError: 'People' object has no attribute 'choice'# print(obj.choice) #print(obj.'name')#但是反射，可以通过字符串操作对象中的属性print("hasattr(obj,'name')===",hasattr(obj,'name')) #等同obj.name #obj.__dict__['name']print("hasattr(obj,'talk')===",hasattr(obj,'talk')) #等同#obj.talkprint("hasattr(obj,'talk12')===",hasattr(obj,'talk12'))print("getattr(obj,'namexxx',None)===",getattr(obj,'namexxx',None))print("getattr(obj,'talk',None)===",getattr(obj,'talk',None))setattr(obj,'sex','male') #obj.sex='male'print("setattr(obj,'sex','male')===",obj.sex)delattr(obj,'age') #del obj.ageprint("delattr(obj,'age')===",obj.__dict__)E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.pyegon<bound method People.talk of <__main__.People object at 0x000001B3F1348940>>hasattr(obj,'name')=== Truehasattr(obj,'talk')=== Truehasattr(obj,'talk12')=== Falsegetattr(obj,'namexxx',None)=== Nonegetattr(obj,'talk',None)=== <bound method People.talk of <__main__.People object at 0x000001B3F1348940>>setattr(obj,'sex','male')=== maledelattr(obj,'age')=== {'name': 'egon', 'sex': 'male'}Process finished with exit code 01.2反射的应用

#!/usr/bin/env python# -*- coding:utf-8 -*-# Author: vita#反射的应用：class Service: def run(self): while True: inp=input('>>: ').strip() #cmd='get a.txt' cmds=inp.split() #cmds=['get','a.txt'] # print(cmds) if hasattr(self,cmds[0]): func=getattr(self,cmds[0]) func(cmds) def get(self,cmds): print('get.......',cmds) def put(self,cmds): print('put.......',cmds)obj=Service()obj.run()print("getattr(obj,'namexxx',None)===",getattr(obj,'namexxx',None))print("getattr(obj,'talk',None)===",getattr(obj,'talk',None))setattr(obj,'sex','male') #obj.sex='male'print("setattr(obj,'sex','male')===",obj.sex)delattr(obj,'age') #del obj.ageprint("delattr(obj,'age')===",obj.__dict__)E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py>>: get a.txtget....... ['get', 'a.txt']2.其他内置方法2.1item系列

__getitem__ obj['name']像字典一样调用属性的时候会触发__getitem__执行__setitem__ obj['age']=22像字典一样设置属性的时候会触发__setitem__执行__delitem__ del obj['age']像字典一样删除属性的时候会触发__delitem__执行#!/usr/bin/env python# -*- coding:utf-8 -*-# Author: vitaclass Foo: #Dict def __init__(self,name): self.name=name def __getitem__(self, item): print('getitem...self.__dict__.get(%s)'%item) # 这里不返回，obj['name']是不会获取到值的，因为这样操作就是执行__getitem__方法 return self.__dict__.get(item) def __setitem__(self, key, value): print("setitem...self.__dict__[%s]=%s"%(key,value)) self.__dict__[key]=value def __delitem__(self, key): print("delitem...del self.__dict__[%s]"%key) del self.__dict__[key]obj=Foo('egon')# 查看属性print(obj.__dict__)# getitem触发时机：obj['name']像字典一样调用属性的时候，会触发print("obj['name']",obj['name']) #结果egonprint("obj['namexx']",obj['namexx']) # 没有，返回Noneprint("obj.name",obj.name) # 这样不会触发__getitem__，必须让字典一样操作才会触发#设置属性obj.sex='male' #这样不会触发__setitem__,但也能给对象添加数据属性print("obj.sex='male'====",obj.__dict__)print("obj.sex======",obj.sex)obj["age"]=22print("obj['age']=22======",obj.__dict__)print("obj.age======",obj.age) #设置后，可以直接使用对象来获取数据属性#删除属性del obj.sex #这样不会触发__del__itemprint("del obj.sex====",obj.__dict__)del obj['age']print("del obj['age']====",obj.__dict__)E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py{'name': 'egon'}getitem...self.__dict__.get(name)obj['name'] egongetitem...self.__dict__.get(namexx)obj['namexx'] Noneobj.name egonobj.sex='male'==== {'name': 'egon', 'sex': 'male'}obj.sex====== malesetitem...self.__dict__[age]=22obj['age']=22====== {'name': 'egon', 'sex': 'male', 'age': 22}obj.age====== 22del obj.sex==== {'name': 'egon', 'age': 22}delitem...del self.__dict__[age]del obj['age']==== {'name': 'egon'}Process finished with exit code 02.2isinstance和issubclass

"isinstance(obj,cls)检查是否obj是否是类 cls 的对象"#!/usr/bin/env python# -*- coding:utf-8 -*-# Author: vitaclass Foo(object): passobj = Foo()print(isinstance(obj, Foo))E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.pyTrueProcess finished with exit code 0

"issubclass(sub, super)检查sub类是否是 super 类的派生类"#!/usr/bin/env python# -*- coding:utf-8 -*-# Author: vitaclass Foo(object): passclass Bar(Foo): passprint(issubclass(Bar, Foo))E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.pyTrueProcess finished with exit code 02.3repr和str

"没有设置这两个方法时"#!/usr/bin/env python# -*- coding:utf-8 -*-# Author: vitaclass School: def __init__(self,name,addr,type): self.name=name self.addr=addr self.type=types1=School('oldboy1','北京','私立')print('from repr: ',repr(s1))print('from str: ',str(s1))print(s1)E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.pyfrom repr: <__main__.School object at 0x000001CC930BEAC8>from str: <__main__.School object at 0x000001CC930BEAC8><__main__.School object at 0x000001CC930BEAC8>Process finished with exit code 0

"可以显式调用repr和str方法,repr和str方法同时存在时，会优先调用str方法，str方法没有时，会调用repr方法repr和str方法都是在print(obj)时调用的，没有这两个方法，输出的是对象的内存地址，有了这两个方法，就可以自行设置有意义的输出"#!/usr/bin/env python# -*- coding:utf-8 -*-# Author: vitaclass School: def __init__(self,name,addr,type): self.name=name self.addr=addr self.type=type def __repr__(self): return 'School(%s,%s)' %(self.name,self.addr) def __str__(self): return '(%s,%s)' %(self.name,self.addr)s1=School('oldboy1','北京','私立')# 可以显式调用repr和str方法print('from repr: ',repr(s1))print('from str: ',str(s1))print('from repr: ',s1.__repr__())print('from str: ',s1.__str__())print(s1)E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.pyfrom repr: School(oldboy1,北京)from str: (oldboy1,北京)from repr: School(oldboy1,北京)from str: (oldboy1,北京)(oldboy1,北京)Process finished with exit code 02.4del

"程序正常结束后，或回收系统资源时如f.close()，会调用__del__"#!/usr/bin/env python# -*- coding:utf-8 -*-# Author: vitaclass Open: def __init__(self,filename): print('open file.......') self.filename=filename def __del__(self): print('回收操作系统资源：self.close()')f=Open('settings.py')print('----main------')

"手动del，会提前执行__del__"#!/usr/bin/env python# -*- coding:utf-8 -*-# Author: vitaclass Open: def __init__(self,filename): print('open file.......') self.filename=filename def __del__(self): print('回收操作系统资源：self.close()')f=Open('settings.py')#程序结束的时候，会自动del f 回收f，就会执行__del__del f # 如果没有这行代码，会先执行print(--main--),之后回收f,运行__del__，如果手动在这里del，就会先执行__del__,然后执行后面语句print('----main------')E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.pyopen file.......回收操作系统资源：self.close()----main------Process finished with exit code 0