class Person:
    def __init__(self, name="Unknown", age=18):
        self.name = name
        self.age = age
<h1>使用默认值创建实例</h1><p>p1 = Person()
print(p1.name, p1.age)  # 输出: Unknown 18</p><h1>提供参数覆盖默认值</h1><p>p2 = Person("Alice", 25)
print(p2.name, p2.age)  # 输出: Alice 25

class MyClass:
    def __init__(self, items=[]):  # 错误！
        self.items = items

class MyClass:
    def __init__(self, items=None):
        if items is None:
            items = []
        self.items = items

class Car:
    brand = "Toyota"   # 类属性，所有实例共享
    wheels = 4
<p>c1 = Car()
print(c1.brand)  # 输出: Toyota</p><p>c1.brand = "Honda"  # 实例修改，只影响该实例
print(c1.brand)     # Honda
print(Car.brand)    # 仍是 Toyota

from dataclasses import dataclass
<p>@dataclass
class Point:
x: int = 0
y: int = 0</p><p>p = Point()
print(p)  # Point(x=0, y=0)