Thoroughly understand Python classes and objects and become a qualified Python developer

1. Classes and Objects

In python, a class is a blueprint for creating objects. Classes contain the data structures and behaviors of objects. Objects are instances of classes. The data structures in a class are called properties, and the behaviors in a class are called methods.

2. Define class

Use the class keyword to define a class. The definition of a class includes the name of the class and the body of the class. The body of a class contains the properties and methods of the class.

For example, the following code defines a class named Person:

class Person:

def __init__(self, name, age):
self.name = name
self.age = age

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

In this class, the __init__ method is a special function that is called when creating an instance of the class. The __init__ method accepts two parameters: self (representing an instance of the class) and name and age (representing the properties of the object).

greetThe method is a normal method that can be called by instances of the class. The greet method accepts one parameter: self (representing an instance of the class).

3. Create object

You can use the class keyword to create an instance of a class. An instance of a class is a concrete object of the class.

For example, the following code creates two instances of the Person class:

person1 = Person("John", 25)
person2 = Person("Mary", 30)

person1 and person2 are two instances of the Person class.

4. Access properties and methods

You can use the . operator to access the properties and methods of a class.

For example, the following code accesses the name attribute of the person1 object:

print(person1.name)

Output:

John

The following code calls the greet method of the person1 object:

person1.greet()

Output:

Hello, my name is John

5. Class inheritance

Python Supports class inheritance. Class inheritance allows one class to inherit the properties and methods of another class.

For example, the following code defines a class named Student, which inherits the Person class:

class Student(Person):

def __init__(self, name, age, major):
super().__init__(name, age)
self.major = major

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

In this class, the __init__ method calls super().__init__ to inherit the attributes and methods of the Person class. studyMethod is a normal method that can be called by instances of a class. The study method accepts one parameter: self (representing an instance of the class).

6. Class polymorphism

Python supports class polymorphism. Class polymorphism allows the same method to have different behaviors for different classes.

For example, the following code defines a function named greet_person that accepts an instance of the Person class as a parameter:

def greet_person(person):
person.greet()

This function can be called on instances of the Person class and its derived classes.

For example, the following code calls the greet_person function to greet person1 and person2:

greet_person(person1)
greet_person(person2)

Output:

Hello, my name is John
Hello, my name is Mary

The above is the detailed content of Thoroughly understand Python classes and objects and become a qualified Python developer. For more information, please follow other related articles on the PHP Chinese website!