#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
简单的计算器程序
"""

def add(a, b):
    """加法运算"""
    return a + b

def subtract(a, b):
    """减法运算"""
    return a - b

def multiply(a, b):
    """乘法运算"""
    return a * b

def divide(a, b):
    """除法运算"""
    if b == 0:
        raise ValueError("除数不能为零")
    return a / b

def calculator():
    """主计算器函数"""
    print("欢迎使用计算器！")
    print("可用操作：+、-、*、/")
    
    try:
        num1 = float(input("请输入第一个数字："))
        operator = input("请输入运算符：")
        num2 = float(input("请输入第二个数字："))
        
        if operator == '+':
            result = add(num1, num2)
        elif operator == '-':
            result = subtract(num1, num2)
        elif operator == '*':
            result = multiply(num1, num2)
        elif operator == '/':
            result = divide(num1, num2)
        else:
            print("无效的运算符")
            return
        
        print(f"结果：{result}")
        
    except ValueError as e:
        print(f"错误：{e}")
    except Exception as e:
        print(f"发生未知错误：{e}")

if __name__ == "__main__":
    calculator()