面向对象——内置方法

isinstance(obj,cls)检查obj是否是类 cls 的对象
issubclass(sub, super)检查sub类是否是 super 类的派生类

 1 # isinstance()#检查obj是否是类 cls 的对象
 2 class Foo(object):
 3     pass
 4 obj = Foo()
 5 print(isinstance(obj,Foo))#True
 6 # issubclass()
 7 class Foo(object):#检查sub类是否是 super 类的派生类
 8     pass
 9 class Bar(Foo):
10     pass
11 print(issubclass(Bar, Foo))#True

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item系列，把obj模拟成字典去操作它的属性
__getitem__，__setitem__，__delitem__

 1 #item系列,把obj模拟成字典去操作它的属性
 2 class Foo:
 3     def __init__(self,name):
 4         self.name = name
 5     def __getitem__(self, item):
 6         # print('getitem...')
 7         return self.__dict__.get(item)
 8     def __setitem__(self, key, value):
 9         # print('setitem...')
10         self.__dict__[key] = value
11     def __delitem__(self, key):
12         # print('delitem...')
13         # self.__dict__.pop(key)
14         del self.__dict__[key]
15 obj = Foo('egon')
16 #查看属性
17 #以前是obj.属性名
18 # obj['name']#  等价于obj.name
19 # print(obj['name'])#egon
20 # print(obj.name)#egon
21 
22 #设置属性：
23 # obj.sex = 'male'
24 # obj['sex'] = 'male'
25 # print(obj.__dict__)
26 # print(obj.sex)
27 
28 #删除属性
29 #del obj.name
30 # del obj['name']
31 # print(obj.__dict__)

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__str__：定制对象的字符串形式

 1 class People:
 2     def __init__(self,name,age):
 3         self.name = name
 4         self.age = age
 5     def __str__(self):
 6         # print('====>str')
 7         return '<name:%s,age:%s>'%(self.name,self.age)
 8 obj = People('egon',18)
 9 print(obj)#obj.__str__()
10 #<name:egon,age:18>

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__del__：析构方法，当对象在内存中被释放时，自动触发执行

 1 class Open:
 2     def __init__(self,filename):
 3         print('open file.....')
 4         self.filename = filename
 5     def __del__(self):
 6         del self.filename
 7         print('回收操作系统资源：self.close()')
 8 f = Open('settings.py')
 9 # del f  #手动，不调用的话是在程序结束后自动调用
10 print('----main----')
11 print(f.filename)
12 """
13 open file.....
14 ----main----
15 settings.py
16 回收操作系统资源：self.close()
17 """

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 1 class Open:
 2     def __init__(self,filename):
 3         print('open file.....')
 4         self.filename = filename
 5     def __del__(self):
 6         del self.filename
 7         print('回收操作系统资源：self.close()')
 8 f = Open('settings.py')
 9 del f  #手动，不调用的话是在程序结束后自动调用
10 print('----main----')
11 # print(f.filename)  #报错
12 """
13 open file.....
14 回收操作系统资源：self.close()
15 ----main----
16 """

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