python反射及其attr系列案例

Posted 2020-09-13

 1 class People:
 2     """
 3  hasattr,setattr,getattr,delattr原理：所有的对象或者类如果有设定相应的key，value,那么在对应的__dict__
 4     这个返回值中都有key,value存在的，
 5 
 6     """
 7     def __init__(self,name):
 8         self.name = name
 9     def walk(self):
10         print(‘%s 瞧，\‘piter\‘ 正在奔跑‘% self.name)
11 P1 = People(‘lucy‘)
12 if hasattr(P1,‘name‘):  #判定如果调用对象P1有name属性，返回True，否则返回False
13     print(P1.__dict__[‘name‘]) #lucy
14 
15 if hasattr(P1,‘age‘):
16     print(P1.__dict__[‘age‘])
17 else:
18     setattr(P1,‘age‘,18)
19     print(P1.__dict__) #{‘age‘: 18, ‘name‘: ‘lucy‘}
20 if hasattr(P1,‘age‘):
21     delattr(P1,‘age‘)  #删除age属性
22 print(P1.__dict__) #{‘name‘: ‘lucy‘}

反射之四大内置函数

#下面是一个菜单的案例，类似反射(反射本质就是把字符串转成对象

 1 def search():
 2     print(‘print search content‘)
 3 def add():
 4     print(‘add content‘)
 5 def delete():
 6     print(‘delete‘)
 7 def modify():
 8     print(‘modify‘)
 9 cmd_dict = {‘search‘:search,‘add‘:add,‘delete‘:delete,‘modify‘:modify}
10 while True:
11     count = 0
12     for i in cmd_dict.keys():
13         count += 1
14         print("%s\t%s"%(count,i))
15     opt = input("请输入选项>>> ")
16     if not opt:continue
17     if opt in cmd_dict:
18         func = cmd_dict.get(opt)
19         func()

菜单案例

内置attr：__getattr__,__setattr__,__delattr__

 1 class Foo:
 2     def __init__(self,name):
 3         self.name = name
 4 
 5     def __getattr__(self, item):  #当属性不存在的情况下才会执行，否则不执行
 6         """如果被调用属性存在就不执行这里定义的代码块，否则的话，会执行这里的代码块"""
 7         print(‘get------%s‘%item,type(item))
 8 
 9     def __setattr__(self,key,value):
10         """设置值，实际上是往调用对象那个__dict__里设定key，并给相应的value"""
11         if not isinstance(value,str):raise  TypeError("must be str")
12         self.__dict__[key] = value
13         print(‘set ----Key:%s,value:%s‘%(key,value),type(key),type(value))
14     def __delattr__(self, item):
15         """删除属性，实际上是把调用对象的__dict__里删除指定的key"""
16         self.__dict__.pop(item)
17         print(‘delete item:%s‘%item,type(item))
18 
19 F = Foo(‘lucy‘)
20 print(F.__dict__)
21 print(F.name)
22 F.age = ‘100‘
23 del F.age
24 print(F.__dict__)
25 F.age = ‘1002‘
26 print(F.age)

反射内置attr应用

 

 

 

 

 

 1 cmd_dict = {‘search‘:search,‘add‘:add,‘delete‘:delete,‘modify‘:modify}
 2 while True:
 3     count = 0
 4     for i in cmd_dict.keys():
 5         count += 1
 6         print("%s\t%s"%(count,i))
 7     opt = input("请输入选项>>> ")
 8     if not opt:continue
 9     if opt in cmd_dict:
10         func = cmd_dict.get(opt)
11         func()

菜单案例