Object-oriented and multi polymorphic states

First, the concept of polymorphism:

In the real world there to understand that is to say, a thing in a variety of forms.

Such as water, solid, gas, liquid, etc.

In the world of the program is that multiple objects of different classes can be obtained by the same method, so that objects of different classes have different results.

It is not a special syntax, but a form.

Advantages: relative to the user, it largely reduces the difficulty of use. More user-friendly

Second, the multi-state implementations and case

Interfaces, abstract classes, duck type, are provided can write code for polymorphic, the simplest type of a duck

Case:

class Chicken:
          DEF Cry (Self):
                 Print ( ' GGGG ' )
          DEF the spawn (Self):
                  Print ( ' the eggs ' )
 class Duck ():
           DEF Cry (Self):
                 Print ( ' Gaga Ga ' )
          DEF the spawn (Self ):
                  Print ( ' the duck ' )      
J = Chicken () 
Y = Duck () 

DEFmany (obj): 
         obj.spawn () 

volume (j) 
number (y)

Third, some of the functions and methods of application:

1，isinstance

This function is used to determine whether an object is an instance of a class

The first parameter is the object of judgment

The second parameter is a need to determine the type of

2，issubclass

This function is used to determine whether a class is a subclass of another class

The first parameter is a subclass of

The second parameter is the parent class

3，_ _str_ _

Str double the results when the object is converted to a string, the conversion is the return value of the function

Be used: it can be used to customize the layout object

4.Del

When you delete an object manually, it will immediately execute the function, or is automatically executed when the program ends

When the object is in use, the resources are not opened interpreter: usage scenarios.

Use Cases:

del 
class FileTool:
        def __init__(self,path):
               self.file = open(path,'rt',encoding = 'utf-8')
               self.a = 100
        def read(self):
              return self.file.read()
         def __del__(self):
                self.file.close()

tool = FileTool('a,txt')

5,call

When performed automatically when the calling object (the object is in parentheses)

6，slots

This property is a class attribute for the object optimizing memory usage

Optimized principle: the original is not a fixed number of attributes, becomes fixed. As a result, the interpreter does not create space for the name of the object, so as to achieve the effect of reducing memory overhead

Will lead to objects of this class can not add new attributes Once the slots in the class

7，getattr,setattr,delattr

getatter when you use point of access to property, if the property does not exist when it will perform

setatter When you use the point to set the property before execution

del delatter with the object when attributes. Will be performed

Fourth, the operator overloading

When we use a symbol, python interpreter will define a meaning for this symbol, while calling the corresponding handler

Originally custom object can not be used directly to compare the size of the operator, but we can customize the operator to achieve, also make custom objects support comparison operators

Object-oriented and multi polymorphic states

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