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This article focuses on "how to understand the object-oriented concepts in Python". Interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how to understand the object-oriented concept in Python.

Two very important concepts of object-oriented programming:

Classes and objects

Object is the core of object-oriented programming. in the process of using objects, another new concept, class, is put forward in order to define a group of objects with common characteristics and behavior.

Class is used to describe a collection of objects with the same properties and methods. It defines the properties and methods common to each object in the collection. Object is an instance of a class.

The class is made up of three parts:

The name of the class

Properties of the class

Methods of the class

The format is as follows:

# class name class Func (object): # property of class item123 # method of class def f (self): print ('6666') # instantiation class a=Func () # access property of class print (A.I) # calling method of class a.f ()

Object is the top-level parent of all classes in Python

The naming rules of class names are in accordance with the "naming method of the Great Hump".

F is an instance method. The first parameter is generally self, which represents the instance object itself. Of course, you can change self to another name, and its function is a variable that points to the instance object.

Magic method 1.init

The method provided in the Python class that starts with two underscores and ends with two underscores is the magic method, and init () is a magic method that is usually used to initialize or assign attributes.

If the class face does not write the _ _ init__ method, the Python will be created automatically, but no action will be performed

If you want to be able to complete the function you want, you can define your own _ _ init__ method

So whether you write a _ _ init__ method or not, there must be a _ _ init__ method in a class

Case study:

# class name class Func (object): def _ _ init__ (self,name,age): property of self.name=name self.age=age # class iDiver123 # method of class def f (self): print ('my name is% s This year% d is'% (self.name,self.age)) # instantiated class a=Func ('Dafei', 24) # access class property print (A.I) # calling class method a.f ()

In init (self), there is a parameter named self by default. If two arguments are passed when creating an object, two parameters are needed in _ _ init__ (self) as the first parameter, for example, _ _ init__ (self,x,y).

Note:

1)。 Get the properties and instance methods inside the class, and get them through self

2)。 Get the properties and instance methods outside the class, through the object name.

3)。 If a class has multiple objects, the properties of each object are saved and have their own independent address

4)。 But the instance method is shared by all objects and takes up only one share of memory space. The class uses self to determine which object called the instance method.

2.str

Str if the _ _ str__ method is defined in a class, the return value of the method is output by default when printing the object, and the address that will return the object is not defined.

Class Func (object): def _ init__ (self,name,age): self.name=name self.age=agea=Func ('Dafei', 24) print (a)

Call the _ _ str__ method, and the output is the return value of the method

Class Func (object): def _ _ init__ (self,name,age): self.name=name self.age=age def _ _ str__ (self): return'my name is% s, and I am% d years old this year'% (self.name,self.age) a=Func ('Dafei', 24) print (a)

Summary: the _ _ str__ () method is called when the object is instantiated. If the _ _ str__ () method is not defined, the address of an object is printed. If _ _ str__ () is defined and there is a return value, the return value is printed.

3.del

When an object is deleted, the python interpreter calls a method by default, which is the _ _ del__ () method

Class Dog (object): def _ _ init__ (self,name): self.name = name print ("_ _ init__ method called") def _ _ del__ (self): print ("_ _ del__ method called") print ("python interpreter started collecting% s object"% self.name) p = Dog ('Bob') del p here I believe you have a deeper understanding of "how to understand the object-oriented concepts in Python", so you might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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