编写节转速度单位Python程序遇NameError：r_kmh未定义求助

错误原因 #

报错核心：r_kmh是to_kmh函数内部的局部变量，仅在该函数内部有效，你在main函数里直接调用show_results(r_kmh)时，Python找不到这个变量，因此抛出NameError。

修复方案 #

1. 先保存转换结果 #

在main函数里，先把to_kmh(knots)的返回值存到变量中，再用这个变量完成打印和调用show_results：

# 替换main里的对应行
kmh_result = to_kmh(knots)
print(kmh_result, "km/h")
show_results(kmh_result)

2. 修正输入循环逻辑 #

原代码输入判断存在漏洞：第一次输入非数字时，循环内直接转int会报错，把输入和判断用while循环包裹更稳妥：

def main():
    system("clear")
    while True:
        user_input = input("What was your speed in knots? ")
        if user_input.isdigit():
            knots = int(user_input)
            mph_result = to_mph(knots)
            print(mph_result, "mp/h")
            kmh_result = to_kmh(knots)
            print(kmh_result, "km/h")
            show_results(kmh_result)
            break
        else:
            print("Invalid response. Please enter a number.")

3. 优化show_results函数 #

原函数print语句有冗余内容，部分分支无return，调整后更简洁合理：

def show_results(speed):
    if speed < 60:
        print("- Go faster")
    elif 60 <= speed < 100:
        print("- Nice one.")
    elif 100 <= speed < 120:
        print("- Radical!")
    elif speed >= 120:
        print("- Whoa! Slow down!")

完整修正后的代码 #

from os import system


def main():
    system("clear")
    while True:
        user_input = input("What was your speed in knots? ")
        if user_input.isdigit():
            knots = int(user_input)
            mph_result = to_mph(knots)
            print(mph_result, "mp/h")
            kmh_result = to_kmh(knots)
            print(kmh_result, "km/h")
            show_results(kmh_result)
            break
        else:
            print("Invalid response. Please enter a number.")


def to_mph(knots):
    mph = 1.1507 * knots
    return round(mph, 1)


def to_kmh(knots):
    kmh = 1.852 * knots
    return round(kmh, 1)


def show_results(speed):
    if speed < 60:
        print("- Go faster")
    elif 60 <= speed < 100:
        print("- Nice one.")
    elif 100 <= speed < 120:
        print("- Radical!")
    elif speed >= 120:
        print("- Whoa! Slow down!")


if __name__ == "__main__":
    main()

内容的提问来源于stack exchange，提问作者Bailey Kelly