Comprehensively master the knowledge of Python classes and objects and become a Python programming master

pythonClasses and Objects

Classes and objects in Python are the basis of Object-orientedprogramming. Classes are templates used to define objects, and objects are instances of classes. Classes provide the properties and methods of objects, and objects contain these properties and methods.

Create class

To create a class, you can use the class keyword. The name of a class should begin with a capital letter to indicate that it is a class. The definition of a class includes the properties and methods of the class. Properties are variables of a class, while methods are functions of a class.

class Person:
name = "John"
age = 20

def greet(self):
print("Hello, my name is", self.name)

The above code defines a class named Person. This class has two attributes: name and age. It also has a method: greet().

Create Object

To create an object, use the class keyword followed by the name of the class. An object is an instance of a class, which contains the properties and methods of the class.

person1 = Person()
person2 = Person()

The above code creates two Person objects. Each object has its own properties and methods.

Access properties and methods

To access the properties or methods of an object, you can use the dot operator .. The left side of the dot operator is the object, and the right side of the dot operator is the name of the property or method.

person1.name = "Mary"
person1.greet()

The above code changes the value of the name attribute of the person1 object to "Mary", and then calls the greet()# of the person1 object ##method.

inherit

Inheritance is an important concept in Python classes. Inheritance allows one class to inherit properties and methods from another class. Derived classes can override the properties and methods of the base class, and can also add new properties and methods.

class Student(Person):
student_id = 12345

def study(self):
print("I am studying.")

The above code defines a class named

Student, which inherits from the Person class. The Student class has its own properties and methods, and it also has the properties and methods of the Person class.

Polymorphism

Polymorphism is an important feature of Python classes and objects. Polymorphism allows different objects to respond differently to the same method. This makes the code more flexible and reusable.

def greet_person(person):
person.greet()

person1 = Person()
person2 = Student()

greet_person(person1)
greet_person(person2)

The above code defines a function named

greet_person(). This function accepts an object as a parameter and calls the object's greet() method. When the person1 object is passed to the function, the function calls the greet() method of the Person class. When the person2 object is passed to the function, the function calls the greet() method of the Student class.

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