Members of the class exercises

1. What is object-oriented private members?

   1.私有类的静态属性
   2.私有对象属性
   3.私有类的方法

2. How to set an object-oriented class methods, and static methods, static methods class method what's the use?

   1.类方法:@classmethod  得到类名可以实例化一个对象,可以操作类的属性
   2.静态方法:@staticmethod保持代码的一致性,提高代码的维护性

3. What property is object-oriented? what's the effect?

   1.@property将动态方法伪装成属性,看起来更加合理

4. What is the role isinstance and issubclass is?

   1.isinstance(a,b)判断a是否是b类的或b类派生类的对象
   2.issubclass(a,b)判断a类是否是b类或b类派生类的子类

5. Look at the code to write the results:

   class A:
       a = 1
       b = 2
       def __init__(self):
           c = 3
   
   obj1 = A()
   obj2 = A()
   obj1.a = 3
   obj2.b = obj2.b + 3
   print(A.a)
   print(obj1.b)
   print(obj2.c)
   
   结果
   1
   2
   报错

6. Look at the code to write the results:

   class Person:
       name = 'aaa'
   
   p1 = Person()
   p2 = Person()
   p1.name = 'bbb'
   print(p1.name)
   print(p2.name)
   print(Person.name)
   bbb
   aaa
   aaa

7. Look at the code to write the results:

   class Person:
       name = []
   
   p1 = Person()
   p2 = Person()
   p1.name.append(1)
   print(p1.name)
   print(p2.name)
   print(Person.name)
   [1]
   [1]
   [1]

8. Look at the code to write the results:

   class A:
   
       def __init__(self):
           self.__func()
   
       def __func(self):
           print('in A __func')
   
   
   class B(A):
   
       def __func(self):
           print('in B __func')
   
   
   obj = B()
   in A __func

9. Look at the code to write the results:

   class Init(object):
   
       def __init__(self,value):
           self.val = value
   
   class Add2(Init):
   
       def __init__(self,val):
           super(Add2,self).__init__(val)
           self.val += 2
   
   class Mul5(Init):
   
       def __init__(self,val):
           super(Mul5, self).__init__(val)
           self.val *= 5
   
   class Pro(Mul5,Add2):
       pass
   
   class Iner(Pro):
       csup = super(Pro)
       def __init__(self,val):
           self.csup.__init__(val)  
           self.val += 1
   # 虽然没有见过这样的写法，其实本质是一样的，可以按照你的猜想来。
   p = Iner(5)
   print(p.val)
   36

10. Follow these requirements, the completion of a commodity.

    • Packaging trade name, original price of goods, as well as a discount.
    • Achieve a real commodity prices get way price.
    • Next complete three methods, the use of a combination of properties complete the following requirements:
      • The method of this property by using the attribute price disguised properties.
      • Use setter decorator decoration and implement the modifications original price of goods.
      • Use deltter decorator decoration and delete the original real property.

    class Goods:
        def __init__(self,name,original_price,discount):
            self.name = name
            self.original_price = original_price
            self.discount =discount
        @property
        def price(self):
            return self.original_price * self.discount
        @price.setter
        def price(self,value):
            self.original_price = value
        @price.deleter
        def price(self):
            del self.original_price
    DY = Goods("大衣",100,0.95)
    print(DY.price)
    DY.price = 1000
    print(DY.price)
    del DY.price
    print(DY.__dict__)