Day 5-3 Polymorphism and Polymorphism

Polymorphism and Polymorphism

duck type

 

 

Polymorphism and Polymorphism

Polymorphism: A kind of thing has many forms. For example, animals have many forms, people, dogs, pigs, leopards. Water also has many forms, ice, snow, water vapor.

1  #Polymorphism : multiple forms of the same thing 
2  import abc
 3  class Animal(metaclass=abc.ABCMeta): #The same thing: animal 
4      @abc.abstractmethod
 5      def talk(self):
 6          pass 
7  
8  class People (Animal): #Animal form one: human 
9      def talk(self):
 10          print ( ' say hello ' )
 11  
12  class Dog(Animal): #Animal form two: dog 
13      def talk(self):
 14          print (' say wangwang ' )
 15  
16  class Pig(Animal): #Animal form 3: Pig 
17      def talk(self):
 18          print ( ' say aoao ' )
 19  
20  class Cat(Animal):
 21      def talk(self) :
 22          print ( ' say miamiao ' )
 23  
24  #Polymorphism : It means that the object can be used directly without considering the type of the object 
25 peo1= People()
 26 dog1= Dog()
 27 pig1= Pig( )
 28cat1= Cat()
 29  
30  # peo1.talk() 
31  # dog1.talk() 
32  # pig1.talk() 
33  
34  def func(animal):
 35      animal.talk() 
func(peo1) # don't care about peo1 Whether it is a pig dog or another type, it can be called and executed directly through this unified func function.

The benefits of polymorphism:

1. Increased program flexibility

　　In order to keep the same, regardless of the ever-changing object, the user calls it in the same form, such as func(animal)

2. Increased program scalability

　A new class is created by inheriting the animal class, and users do not need to change their own code, or use func(animal) to call 　

Duck Type:

That is, if it looks like a duck, walks like a duck and quacks like a duck, then it's a duck.

1  # Both are ducks, both look like files, so they can be used as files 
2  class TxtFile:
 3      def read(self):
 4          print ( " text is reading " )
 5  
6      def write(self ):
 7          pass 
8  
9  class DiskFile:
 10      def read(self):
 11         print ( " disk is reading " )
 12      def write(self):
 13          pass 
14  
15 text = TxtFile()
 16 disk = DiskFile()
17 
18 text.read()
19 disk.read()

 Duck type, don't need to inherit abstract class, just write the method attributes in the two types similar. That's it.