Python 3函数

Question

在我的课堂上，我们正在学习如何使用函数，我永远也找不出我在这里做错了什么。我们必须计算一次旅行后的汽油费用，虽然我的程序还没有完成，但这就是我到目前为止所拥有的。

MPG_HIGHWAY = 39
MPG_CITY = 28
GALLON = 2.29

def main():
    total_miles = float(input('Enter the total number of miles driven: '))
    highway_percentage = float(input('Enter your percentage of time on the highway: '))
    gas_expense()

def total_highway_miles(total_miles, highway_percentage):
    total_highway_miles = total_miles * highway_percentage
    return total_highway_miles

def total_city_miles(total_miles, total_highway_miles):
    total_city_miles = total_miles - total_highway_miles
    return total_city_miles

def gas_expense(total_highway_miles, total_city_miles):
    total_miles = (total_highway_miles / MPG_HIGHWAY) + (total_city_miles / MPG_CITY)
    gas_expense = total_miles * GALLON

main()

我似乎不能正确地调用变量，这样它就可以在用户输入之后计算信息。不知道我在哪里出错了，但如果能帮我指明正确的方向，那就太好了。谢谢!

Answer 1

您的错误消息应该会告诉您哪里出了问题。在运行代码并提供一些输入后，您将获得

回溯(最近一次调用)：主TypeError中文件"“的第1行，文件"”的第4行: gas_expense()恰好接受2个参数(给定0)

因此，查看引用的代码，我们会发现：

gas_expense()

作为函数调用，但实际的函数签名是

def gas_expense(total_highway_miles, total_city_miles):

您需要将这些值传递给函数以使其保持良好状态。

Answer 2

希望这能有所帮助。所以，首先你有这些常量：

MPG_HIGHWAY = 39
MPG_CITY = 28
GALLON = 2.29

这些常量可以在所有函数中使用。但仅在gas_expense中使用。

您希望通过调用函数main()来计算燃气费

def main():
    total_miles = float(input('Enter the total number of miles driven: '))
    highway_percentage = float(input('Enter your percentage of time on the highway: '))
    gas_expense()

在这里，您没有在上面的函数中使用total_miles和highway_percentage的值，您只需要输入值。此外，gas_expense()还会产生一个错误，因为您已经将其定义为：

def gas_expense(total_highway_miles, total_city_miles):
        total_miles = (total_highway_miles / MPG_HIGHWAY) + (total_city_miles / MPG_CITY)
        gas_expense = total_miles * GALLON

因此，函数gas_expense需要两个输入。例如：gas_expense(100, 200)不会产生错误。

此外，x = gas_expense(100, 200)还会产生一个错误。因为这只会做(计算)你在函数中告诉的事情，而不会返回任何值。返回值的步骤：

def gas_expense(total_highway_miles, total_city_miles):
        total_miles = (total_highway_miles / MPG_HIGHWAY) + (total_city_miles / MPG_CITY)
        gas_expense = total_miles * GALLON
        return gas_expense

例如：x = gas_expense(100, 200)将导致x的值为22.2289377。

但是..我可能建议函数和变量不要使用相同的名称。

使用其他两个函数：total_highway_miles和total_city_miles没有任何问题。要获得气体费，主要函数可以是：

def main():
        total_miles = float(input('Enter the total number of miles driven: '));
        highway_percentage = float(input('Enter your percentage of time on the highway: '));
        x = total_highway_miles(total_miles, highway_percentage);
        y = total_city_miles(total_miles, x);
        return gas_expense(x, y)

Answer 3

下面的代码将帮助您了解代码中的错误所在。

MPG_HIGHWAY = 39
MPG_CITY = 28
GALLON = 2.29

def main():
    total_miles = float(input('Enter the total number of miles driven: '))
    highway_percentage = float(input('Enter your percentage of time on the highway: '))

    thm = total_highway_miles(total_miles, highway_percentage)
    tvm = total_city_miles(total_miles, thm)

    gas_expense(thm, tvm)

def total_highway_miles(total_miles, highway_percentage):
    return total_miles * highway_percentage

def total_city_miles(total_miles, total_highway_miles):
    return total_miles - total_highway_miles

def gas_expense(total_highway_miles, total_city_miles):
    total_miles = (total_highway_miles / MPG_HIGHWAY) + (total_city_miles / MPG_CITY)
    gas_expense = total_miles * GALLON

main()