Class: Think of it as a "car blueprint."

The blueprint defines what the car should have (engine, frame, tires, etc.)

• Data (Attributes): color, top speed, fuel tank capacity, current fuel level...
• Functions (Methods): press the accelerator to speed up, press the brake to slow down...

But a blueprint isn't a real car — you can't drive a blueprint on the road.

Object: A real car built according to the blueprint.

The red Audi in your garage is my object, and the blue BMW parked downstairs is another object. Both were built from the same blueprint (class), but each has its own color, its own fuel level, and neither affects the other.

The essence: A class is an abstract template; an object is a concrete instance.

1. What Is a Class?

In code, a class is auser-defined data type that bundles data together with methods that operate on that data.

A complete class typically contains the following parts:

• Attributes (Fields / Member Variables): describe the object's state, e.g., color, speed.
• Methods (Member Functions): describe what the object can do, e.g., accelerate(), brake().
• Constructor: a special method that is automatically called when creating an object, used to initialize its attributes.

Here is the simplest Car class written in Python:

# 汽车类
class Car：

# 类变量：所有实例共享，好比“四轮汽车的共识”
wheels = 4


# 构造方法初始化每个对象独有的状态
def __init__(self,color,max_speed):
  # 实例变量：每个对象各自拥有
  self.color = color
  self.max_speed = 0
  self.fuel = 100

# 方法：加速行为
def accelerate(self,amout):
  self.current_speed += amount
  self.fuel -= amount * 0.1
  print(f"加速至{self.current_speed} km/h,剩余油量{self.fuel}")
  

2. What Is an Object?

An object is the concretization and instantiation of a class. You use the class as a mold to "press" an entity into memory — this process is called instantiation.

A single class can produce countless objects; each object possesses the attributes and methods defined in the class, but their attribute values are independent of one another.

Continuing the example above, let's build two cars using the Car class:

my_car = Car("红sai",200)           # Car对象A
your_car = Car("蓝sai",220)         # Car对象B

my_car.accelerate(50)               # 输出：加速度至50km/h，剩余油量95.0
your_car.accelerate(30)             # 输出：加速度至30km/h，剩余油量97.0

print(my_car.color)                 # 输出：红sai
print(your_car.color)               # 输出：蓝sai

他们共享类变量
print(my_car.wheels)                # 输出：4
print(your_car.wheels)              # 输出：4

In memory, my_car and your_car occupy two independent spaces. Changing my_car's fuel level does not affect your_car.

"A class defines the type of an object, and an object is an instance of a class."