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

• # isinstance()#检查obj是否是类 cls 的对象
  class Foo(object):
      pass
  obj = Foo()
  print(isinstance(obj,Foo))#True
  # issubclass()
  class Foo(object):#检查sub类是否是 super 类的派生类
      pass
  class Bar(Foo):
      pass
  print(issubclass(Bar, Foo))#True

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

• #item系列,把obj模拟成字典去操作它的属性
  class Foo:
      def __init__(self,name):
          self.name = name
      def __getitem__(self, item):
          # print('getitem...')
          return self.__dict__.get(item)
      def __setitem__(self, key, value):
          # print('setitem...')
          self.__dict__[key] = value
      def __delitem__(self, key):
          # print('delitem...')
          # self.__dict__.pop(key)
          del self.__dict__[key]
  obj = Foo('egon')
  #查看属性
  #以前是obj.属性名
  # obj['name']#  等价于obj.name
  # print(obj['name'])#egon
  # print(obj.name)#egon
  
  #设置属性：
  # obj.sex = 'male'
  # obj['sex'] = 'male'
  # print(obj.__dict__)
  # print(obj.sex)
  
  #删除属性
  #del obj.name
  # del obj['name']
  # print(obj.__dict__)

• __str__：定制对象的字符串形式

• class People:
      def __init__(self,name,age):
          self.name = name
          self.age = age
      def __str__(self):
          # print('====>str')
          return '<name:%s,age:%s>'%(self.name,self.age)
  obj = People('egon',18)
  print(obj)#obj.__str__()
  #<name:egon,age:18>

• __del__：析构方法，当对象在内存中被释放时，自动触发执行

• class Open:
      def __init__(self,filename):
          print('open file.....')
          self.filename = filename
      def __del__(self):
          del self.filename
          print('回收操作系统资源：self.close()')
  f = Open('settings.py')
  # del f  #手动，不调用的话是在程序结束后自动调用
  print('----main----')
  print(f.filename)
  """
  open file.....
  ----main----
  settings.py
  回收操作系统资源：self.close()
  """

• class Open:
      def __init__(self,filename):
          print('open file.....')
          self.filename = filename
      def __del__(self):
          del self.filename
          print('回收操作系统资源：self.close()')
  f = Open('settings.py')
  del f  #手动，不调用的话是在程序结束后自动调用
  print('----main----')
  # print(f.filename)  #报错
  """
  open file.....
  回收操作系统资源：self.close()
  ----main----
  """