如何在没有所需参数的情况下调用函数？

def greet(name="Guest"):
    print("Hello, " + name + "!")

greet()  # 输出：Hello, Guest!
greet("Alice")  # 输出：Hello, Alice!

def sum_numbers(*numbers):
    total = 0
    for num in numbers:
        total += num
    return total

print(sum_numbers(1, 2, 3))  # 输出：6
print(sum_numbers())  # 输出：0

def greet():
    name = input("请输入您的名字：")
    print("Hello, " + name + "!")

greet()  # 输出：根据用户输入的名字打印问候语