对第二个功能感到困惑

Question

我对我的代码感到困惑，我认为我做的一切都是正确的，但我不确定如何让我的代码的第二部分工作，即“total_costs”函数。我现在看了很多视频，但似乎找不到关于这个的，有人可以向我解释为什么我的代码的第二部分不能工作吗？

def get_input():
    e1 = float(input("What is the monthly expense for House Payment. "))
    e2 = float(input("What is the monthly expense for Homeowners Insurance. "))
    e3 = float(input("What is the monthly expense for Car Payments. "))
    e4 = float(input("What is the monthly expense for Car Insurance. "))
    e5 = float(input("What is the monthly expense for Utilities. "))
    print("The monthly expenses total to",format(monthly, ',.2f'))
    print("The yearly expenses total to",format(yearly, ',.2f'))
    

def total_costs():
    monthly = e1 + e2 + e3 + e4 + e5
    yearly = monthly * 12
    return monthly, yearly
    
    

get_input()

Answer 1

您使用 e1,e2,e3,e4,e5 作为函数变量，因此范围仅限于 get_input 函数，您不能在 get_input 函数之外使用这些变量，除非您全局指定它们。

而且你没有调用total_cost函数。

问题是您在本地范围内使用变量而不是调用函数。

Answer 2

您的代码存在一些问题。首先，你没有调用total_costs()，所以它永远不会被执行。你也没有捕捉到结果。

让我们重新安排一下：

def get_input():
    e1 = float(input("What is the monthly expense for House Payment. "))
    e2 = float(input("What is the monthly expense for Homeowners Insurance. "))
    e3 = float(input("What is the monthly expense for Car Payments. "))
    e4 = float(input("What is the monthly expense for Car Insurance. "))
    e5 = float(input("What is the monthly expense for Utilities. "))
    monthly, yearly = total_costs()
    print("The monthly expenses total to",format(monthly, ',.2f'))
    print("The yearly expenses total to",format(yearly, ',.2f'))

def total_costs():
    monthly = e1 + e2 + e3 + e4 + e5
    yearly = monthly * 12
    return monthly, yearly
    
get_input() 

更好，但是当你尝试时，它会抱怨不知道e1。这是因为虽然看起来是这样，但 total_costs 并不知道 e1 和其他变量。您需要显式传递它。

#!/usr/bin/env python3
def get_input():
    e1 = float(input("What is the monthly expense for House Payment. "))
    e2 = float(input("What is the monthly expense for Homeowners Insurance. "))
    e3 = float(input("What is the monthly expense for Car Payments. "))
    e4 = float(input("What is the monthly expense for Car Insurance. "))
    e5 = float(input("What is the monthly expense for Utilities. "))
    monthly, yearly = total_costs(e1, e2, e3, e4, e5)
    print("The monthly expenses total to",format(monthly, ',.2f'))
    print("The yearly expenses total to",format(yearly, ',.2f'))

def total_costs(e1, e2, e3, e4, e5):
    monthly = e1 + e2 + e3 + e4 + e5
    yearly = monthly * 12
    return monthly, yearly
    
get_input() 

现在一切正常，正如您所期望的那样。现在你不一定会像这样构造你的代码。例如，您在get_input 中所做的事情并不需要它自己的函数，而是可能拥有像e1 这样的所有这些单个变量，您可以拥有一个像列表或字典这样的结构，您可以传递给total_costs，不过你很快就会知道的。

Answer 3

total_costs 无处被调用。

Answer 4

首先，total_costs() 没有被调用。如果它没有被调用，你怎么能期望它被执行？

其次，甚至如果你打电话给total_costs，它仍然会给出NameError: name 'e1' is not defined。这是因为get_input()中的变量是局部变量，所以在get_input()函数结束时会被删除。

因此，您需要从get_input() 返回变量，或者使用global 关键字使它们不限于get_input()，尽管我强烈建议您使用第一种方法，因为global 使调试成为一场噩梦。

代码：

def get_input():
    e1 = float(input("What is the monthly expense for House Payment. "))
    e2 = float(input("What is the monthly expense for Homeowners Insurance. "))
    e3 = float(input("What is the monthly expense for Car Payments. "))
    e4 = float(input("What is the monthly expense for Car Insurance. "))
    e5 = float(input("What is the monthly expense for Utilities. "))
    print("The monthly expenses total to",format(monthly, ',.2f'))
    print("The yearly expenses total to",format(yearly, ',.2f'))
    return e1,e2,e3,e4,e5

def total_costs():
    monthly = e1 + e2 + e3 + e4 + e5
    yearly = monthly * 12
    return monthly, yearly

get_input()
total_costs()

或

def get_input():
    global e1,e2,e3,e4,e5
    e1 = float(input("What is the monthly expense for House Payment. "))
    e2 = float(input("What is the monthly expense for Homeowners Insurance. "))
    e3 = float(input("What is the monthly expense for Car Payments. "))
    e4 = float(input("What is the monthly expense for Car Insurance. "))
    e5 = float(input("What is the monthly expense for Utilities. "))
    print("The monthly expenses total to",format(monthly, ',.2f'))
    print("The yearly expenses total to",format(yearly, ',.2f'))

def total_costs():
    monthly = e1 + e2 + e3 + e4 + e5
    yearly = monthly * 12
    return monthly, yearly

get_input()
total_costs()