Python中的名称错误和函数 [英] NameErrors and functions in python

问题描述

  def today（）：
 day = input（它是哪一天？）
 
如果在星期日为星期日：
 day = 0 
 elif daydayin day：
 day = 1 
 eliftuesdayin day：
 day = 2 
 elifwednesdayin day：
 day = 3 
 elifthursdayin day：
 day = 4 
 eliffridayin day：
 day = 5 
 elifsaturdayin day：
 day = 6 
 
 else：
 today（）
 today（）
 
 days_on_vacation = int（input（你会度假多少天））
 
 days_to_add_to_day = days_on_vacation％7 
 
 day + = days_to_add_to_day 
  

我已经给函数 today（）赋值了一天吗？为什么我被告知它没有被定义？

解决方案

您在函数中分配的名称是 locals ;它们在函数之外是不可见的。

分享这个结果的最好方法是从函数中返回值，这样你可以将它分配给一个变量作为调用的结果：

$ $ p $ def today（）：
＃...
回报日

和

 result = today（）
  

result 变量然后保存函数返回的值。您可以自由使用名称 day 那里，但那是一个与函数内部的变量分离的变量。

你通过使用递归函数调用使事情变得复杂;您还需要确保将递归调用的结果传递回链中：

  def today（）： 
＃... 
 else：
今天返回（）
返回日
  

但是，最好不要在这里依赖递归;一个简单的无限循环会做得更好;

  def today（）：
而真：
 day = input（'...'）
＃... 
 else：
＃无效输入，重启循环
 continue 
 
＃输入有效，返回结果
返回日
  

I'm constantly getting a NameError Although I already defined a term, The problem is with "day" on line 28.

def today():
    day = input("What day is it?")

    if "sunday" in day:
        day = 0
    elif "monday" in day:
        day = 1
    elif "tuesday" in day:
        day = 2
    elif "wednesday" in day:
        day = 3
    elif "thursday" in day:
        day = 4
    elif "friday" in day:
        day = 5
    elif "saturday" in day:
        day = 6

    else:
        today()
today()

days_on_vacation = int(input("How many days will you be on vacation?   "))

days_to_add_to_day = days_on_vacation % 7

day += days_to_add_to_day

I already gave day a value in the function today() right? Why am I being told it is not defined?

解决方案

Names you assign to in a function are locals; they are not visible outside of the function.

The best way to share that result is to return the value from the function, so that you can assign it to a variable as a result of the call:

def today():
    # ...
    return day

and

result = today()

The result variable then holds the value the function returned. You are free to use the name day there too but that's then a separate variable from the one inside the function.

You did complicate matters here by using a recursive function call; you then also need to make sure you pass on the result of the recursive calls back along the chain:

def today():
    # ...
    else:
        return today()
    return day

However, it is better not to rely on recursion here; a simple enless loop would do a better; returning from the function would automatically end the loop:

def today():
    while True:
        day = input('...')
        # ...
        else:
            # not valid input, restart the loop
            continue

        # input was valid, return the result
        return day

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