如何省略可选函数，即参数

def greet(name, greeting="Hello"):
    return f"{greeting}, {name}!"

# 调用时可以省略 greeting 参数
print(greet("Alice"))       # 输出: Hello, Alice!
print(greet("Bob", "Hi"))   # 输出: Hi, Bob!

def create_user(username, email, age=None):
    user_info = {
        "username": username,
        "email": email,
    }
    if age is not None:
        user_info["age"] = age
    return user_info

# 使用关键字参数调用
user1 = create_user(username="john_doe", email="john@example.com")
user2 = create_user(username="jane_doe", email="jane@example.com", age=30)

class UserParams:
    def __init__(self, username, email, age=None):
        self.username = username
        self.email = email
        self.age = age

def create_user(params: UserParams):
    user_info = {
        "username": params.username,
        "email": params.email,
    }
    if params.age is not None:
        user_info["age"] = params.age
    return user_info

# 使用参数对象调用
user_params = UserParams(username="john_doe", email="john@example.com")
user1 = create_user(user_params)