！/usr/bin/env python3
#-*- coding:utf-8 -*-
# write by congcong# 反射：通过字符串映射到对象的属性
class People:def __init__(self,name,age):self.name = nameself.age = agedef study(self): # 绑定对象方法print('%s is  studying now'%self.name)
p1 = People('cc',21)
print(p1.name) # cc
# hasattr(obj,str) 判断字符串所对应的属性是否在指定对象中存在

print(hasattr(p1,'name')) # True print(hasattr(p1,'study')) # True print(hasattr(People,'study')) # True print(hasattr(People,'name')) # False 

# getattr(obj,str,None) 获取对象中字符串对应的属性，没有时返回None 

print(getattr(p1,'name',None)) # cc print(getattr(p1,'study',None)) # <bound method People.study of <__main__.People object at 0x0000024C49773320>> print(getattr(People,'name',None)) # None print(getattr(People,'study',None)) # <function People.study at 0x000001AEE4128B70>  

# setattr(obj,str) # 设置属性,添加或修改属性 

setattr(p1,'sex','male') setattr(p1,'age',22) setattr(People,'country','China') print(p1.__dict__) # {'name': 'cc', 'age': 22, 'sex': 'male'} print(People.__dict__) # {'__module__': '__main__', '__init__': <function People.__init__ at 0x00000164440C8AE8>, 'study': <function People.study at 0x00000164440C8B70>, '__dict__': <attribute '__dict__' of 'People' objects>, '__weakref__': <attribute '__weakref__' of 'People' objects>, '__doc__': None, 'country': 'China'}

# delattr(obj,str)  删除属性

delattr(p1,'sex') delattr(People,'country') print(p1.__dict__) # {'name': 'cc', 'age': 22} print(People.__dict__) 

# {'__module__': '__main__', '__init__': <function People.__init__ at 0x0000021A437E8AE8>, 'study': <function People.study at 0x0000021A437E8B70>, '__dict__': <attribute '__dict__' of 'People' objects>, '__weakref__': <attribute '__weakref__' of 'People' objects>, '__doc__': None}

import commonsdef run():inp = input("请输入您想访问页面的url： ").strip()modules, func = inp.split("/")obj = __import__("lib." + modules, fromlist=True) # 注意fromlist参数if hasattr(obj, func):func = getattr(obj, func)func()else:print("404")if __name__ == '__main__':run()

请输入您想访问页面的url： commons/home
这是网站主页面！
请输入您想访问页面的url： account/find
这是一个查找功能页面！

# 反射的应用
class Handle:def run(self):exit_flag = Falsewhile not exit_flag:user_in = input('>>:').strip()hand_cmd = user_in.split()if hasattr(self,hand_cmd[0]):func = getattr(self,hand_cmd[0])func(hand_cmd)elif user_in=='q':exit_flag=Trueelse:print('error input')def put(self,hand_cmd):print('putting now',hand_cmd)def get(self,hand_cmd):print('getting now',hand_cmd)
f = Handle()
f.run()

View Code

class Func(object):pass
obj = Func()
print(isinstance(obj, Func)) # True

class Foo(object):pass
class Bar(Foo):pass
print(issubclass(Bar, Foo)) # True

class Func():def __init__(self,name):self.name = namedef __getitem__(self, item): print('from getitem')return self.__dict__.get(item)def __setitem__(self, key, value): print('from setitem')　　　　 self.__dict__[key] = value def __delitem__(self, key): print('from delitem')　　　　 # print('del obj[key]时，执行')del self.__dict__[key]  　　　　 self.__dict__.pop(item)
p1 = Func('cc')
print(p1.__dict__) # {'name': 'cc'}# 查看属性
print(p1['name'])  # from getitem    cc 触发__getitem__
print(p1.name)   # cc# 设置属性
# p1.sex = 'male' # 不会触发__setitem__
p1['sex'] = 'male' # from setitem  会触发__setitem__

p1['name'] = 'SC'p1['age'] = 21
print(p1.__dict__)  # {'name': 'SC', 'sex': 'male', 'age': 21}

# 删除属性 # del p1.sex  # 不会触发__delitem__del p1.agedel p1['sex'] # 触发__delitem__,输出:from delitem

print(p1.__dict__) # {'name': 'SC'}

# __setattr__,__delattr__,__getattr__
class Fun:x=1def __init__(self,y):self.y = ydef __getattr__(self, item):print("---> from getattr:你寻找的属性不存在")def __setattr__(self, key, value):print("--->from setattr")# self.key = value #无限递归self.__dict__[key]=value # 正确姿势

def __delattr__(self, item):print("--->from delattr")# del self.item #无限递归self.__dict__.pop(item)# __setattr__添加/修改属性会触发它的执行
f1 = Fun(66)
print(f1.__dict__) # --->from setattr {'y': 66} 因为重写了__setattr__，凡是赋值操作都会触发它的执行
f1.z = 666
print(f1.__dict__) # --->from setattr  {'y': 66, 'z': 666}# __getattr__只有在使用点调用属性且属性不存在时才会触发
print(f1.y) # 66
print(f1.xx) # ---> from getattr:你寻找的属性不存在# __delattr__删除属性的时候会触发
f1.__dict__['aa'] = 6688 print(f1.__dict__)  #{'y': 66, 'z': 666, 'aa': 6688}

del f1.aa # 触发__delattr__,输出： --->from delattr print(f1.__dict__) # {'y': 66, 'z': 666}

del f1.__dict__['y'] #未触发__delattr__print(f1.__dict__) # {'z': 666}

class Str:def __init__(self,name,age):self.name = nameself.age = agedef __str__(self):return '<name:%s  age: %s>'%(self.name,self.age)  # 必须有返回值
msg = Str('hello',999)
print(msg) # <name:hello  age: 999>  打印对象时触发__str__方法，实现定制化输出

# 回收操作系统的资源
class Open:def __init__(self,filename):print('open file now')self.filename = filenamedef __del__(self):    # 相当于self.close()等关闭操作，在此方法中进行Python不能自动回收的资源回收操作print('回收系统资源')
f = Open('settings.py')   # 包含两部分操作，一是Python解释器开辟一块内存并赋给f,二是在系统硬盘层面打开了一个文件
print('End...')  # 触发del f --> f.__del__(Python程序结束会自动回收程序中的变量，对象，但不能关闭系统资源)
'''
open file now
End...
回收系统资源
'''