A detailed example of Python class analysis

This article mainly introduces the Python class details and examples of relevant information, the need for friends can refer to the following

Python class explanation

Class

1. A class is a data structure that you can use to create instances. (Typically, the class encapsulates the data and the methods that are available for that data)

The 2.Python class is a callable object, that is, a class object

3. Classes are typically defined at the top level of the module so that class instances can be created anywhere in the source code file defined by the class.

4. Instance initialization

1. Instance = ClassName (args ....)

2. Classes can use the Init and Del two special methods when instantiating.

Class ClassName (Base): ' Class documentation string ' #类文档字符串 class suite        #类体

1. Base: A superclass is one or more collections of parent classes for inheritance

2. The class body can include: Declaration statements, class member definitions, data properties, methods

3. If the class does not have an inheritance relationship, the base in parentheses is not provided

Class FirstClass ():  spam =    #类数据属性  def display (self): #类方法   print Self.spam x = FirstClass ()   # Create class instance X.display ()     #方法调用 >>> dir (firstclass) >>> [' Doc ', ' module ', ' Display ', ' spam ']

• The class statement is like Def, which is executable code, and classes are not created until the class statement is run

• Class statement, any assignment statement will create a property

• Each instance object inherits the properties of the class and obtains its own namespace

Python class methods and calls

An instance (object) contains properties

• Callable Properties: Methods

• Data properties

In OOP, instances are like records with "data", and classes are "programs" that process these records

• Invoking a method through an instance is equivalent to invoking the method of the owning class to handle the current instance. For example, the previous code example, X.display () is automatically converted to Firstclass.display (x), the method that invokes the class to process the instance X

• Therefore, each method in a class must have a self parameter, which implies the current instance's meaning

• Assigning an assignment to the Self property within a method results in each instance's own properties

• Python stipulates that there is no instance, the method is not allowed to be called, this is the concept of ' bind ' (binding)

• The assignment statement in the class statement creates a class attribute, as in the previous example spam

• Assigning the special parameter self to a method in a class method creates an instance property

Python Builder

When you create an instance, Python automatically calls the Init method in the class to provide an invisible property for the instance

1. The Init method is called the constructor

2. If the Init method is not defined in the class, the instance is created simply as a simple namespace.

3. The first argument to Init must be self, and the self variable is used to refer to the instance that the method is bound to in the class instance method. Because an instance of a method is always passed as the first argument in any method call, self is selected to represent the instance. You must put self in the method declaration, but you can not use the instance (self) in the method. If you don't use self in your method, consider creating a regular function unless you have a particular reason. After all, your method code does not use an instance, it does not associate its functionality with the class, which makes it look more like a regular function. In other object-oriented languages, self may be referred to as this.

• Init cannot return any objects

• destructor: Del

• Constructors are necessary, and destructors are often not considered (the Python interpreter recycles itself)

Class MyClass (): Def init (self, name):  self.name = name  print ' My name is ' + Self.name def del (self):  print S Elf.name + ' is dead. ' I1 = MyClass (' Shaw's ') >>> My name is Shawdel i1>>> Shaw ID dead.

Special properties of the class

• Use Dir () or Dict to view the properties of a class or instance

• Doc: Get the document string

• Base: Get all parent classes

• Module: Modules in which the class resides

• Name: Names of classes to which the instance belongs

Variables available in the Python class method

• Instance variable: Self. Variable name

• Local variable: A variable created inside a method that can be used directly

• Static variable: A variable defined in a class. Class name. Variable name

• Global variables: Direct use

Inherited

Inheritance describes how the properties of a base class are ' inherited ' to derived classes

1. Subclasses can inherit any property of his base class, including data properties and methods

2. A class that does not specify a base class, which has a base class called object by default

3. Python allows multiple inheritance (multiple parent classes can be inherited)

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