Creating classes in Python requires understanding the structure and usage scenarios. 1. Use class to define the class and initialize the properties through \_\_init\_\_, such as class Person: def \_\_init\_\_(self, name, age): self.name = name; self.age = age. 2. The method is used to operate attributes and must contain self parameters, such as say_hello and update_age methods. 3. Classes are templates, instances are specific objects, and each has independent attributes; class attributes are shared by all instances, modifying class attributes affects all instances, but modifying instance attributes alone does not affect other instances. Master these core points and write Python classes with clear functions.
Creating a class in Python is not difficult, the focus is on understanding the basic structure and usage scenarios of the class. Simply put, a class is a template for creating an object, which you can use to define the properties and methods of an object. Next, let’s take a look at how to write a Python class step by step.
Define the basic structure of a class
Python uses the class keyword to define a class, and the basic format is as follows:
class class name:
# Properties and methodsFor example, if we want to define a class that represents "people", we can write it like this:
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
def says_hello(self):
print(f"Hello, my name is {self.name}")Here are a few key points:
-
__init__is a constructor used to initialize the properties of an object. -
selfmeans the instance itself and must be passed in as the first parameter. -
say_hellois an instance method that can be called on an object.
Add properties and methods
The core function of a class is to encapsulate data and behavior. Attributes are usually variables, and methods are functions.
Common practices:
- Initialize attributes in
__init__ - Define other methods to manipulate these properties
For example, we can add a method to modify the age of Person class above:
def update_age(self, new_age):
if new_age > 0:
self.age = new_ageYou can also add a method to calculate age in ten years:
def age_in_ten_years(self):
return self.age 10 Note: Do not forget to add self parameter in the method, otherwise an error will be reported during runtime.
The relationship between classes and instances
A class is a blueprint, and an instance is a specific object. for example:
p1 = Person("Alice", 30)
p2 = Person("Bob", 25) These two instances are independent, each with their own name and age .
You can also add class attributes to the class, which are shared by all instances:
class Person:
species = "Human"
print(p1.species) # output Human
print(p2.species)If you modify the class attributes:
Person.species = "AI" print(p1.species) # Become AI
But if you only modify the properties of one instance, it will not affect other instances:
p1.species = "Robot" print(p1.species) # Robot print(p2.species) # Still AI
Basically that's it. By mastering the use of class structures, constructors, properties and methods, you can write Python classes with clear functions. In actual development, advanced features such as inheritance and static methods can also be used, but that is the next step.
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