python编写一个函数，该函数能比较三个数的大小并调用

在Python中，你可以编写一个名为`compare_numbers`的函数，用于比较三个数的大小。这里是一个简单的实现示例：

def compare_numbers(num1, num2, num3):
    if num1 > num2 and num1 > num3:
        return f"{num1} is the largest."
    elif num2 > num1 and num2 > num3:
        return f"{num2} is the largest."
    else:
        return f"{num3} is the largest."

# 测试函数
print(compare_numbers(5, 3, 7))  # 输出 "7 is the largest."
print(compare_numbers(1, 9, 4))   # 输出 "9 is the largest."
print(compare_numbers(0, -2, 0))  # 输出 "0 is the largest." (因为相等视为最小)