我程序的函数python .extend()出了点问题 [英] something wrong with my program's function python .extend()

问题描述

当我在python中为程序创建函数时，遇到了一个问题.每次我运行程序时，输入所需的内容后，我总是收到一条错误消息:"AttributeError:'NoneType'对象没有属性'extend'"该程序是:

while I was creating a function for a program in python, I encountered a problem. every time I run the program, after inputting what's needed I always get an Error saying: "AttributeError: 'NoneType' object has no attribute 'extend'" the program is:

def getDoubleList (generalPrompt, sentinel):
END="not end"
OUT= []
print(generalPrompt)
while END.upper() != sentinel.upper():
    IN=input(">")
    END=IN.upper()
    if IN.upper() != sentinel.upper():
        IN=list((IN).split(" "))                
        OUT=(OUT.extend(IN))
return OUT
#testing part (no editing below this point)
nums = getDoubleList("Enter a list of numbers:", "end")
print("Your numbers (sorted):")
for n in sorted(nums):
    print(n)

当我运行它时，我得到以下信息:

And when i run it i get the following:

Enter a list of numbers:
>2 3
>3
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
[...]
        nums = getDoubleList("Enter a list of numbers:", "end")
      File "C:/Users/admin/Downloads/getDoubleDriver.py", line 12, in getDoubleList
        OUT=(OUT.extend(IN))
    AttributeError: 'NoneType' object has no attribute 'extend'

但是我的函数中没有任何nonetypes.我不知道尝试查找问题的功能出了什么问题，但没有

however I don't have any nonetypes within my function. I don't know what went wrong in the function i tried to look for the problem but without

推荐答案

.extend 是就地方法，它不返回任何内容，它会修改您的列表.

.extend is in-place method, it does not return anything, it modifies your list.

查看示例

>>> print [].extend([3])
None

或

>>> x = []
>>> print x
[]
>>> y = x.extend([4])
>>> print y
None
>>> print x
[4]

因此要解决问题，只需更改

thus to solve the problem, simply change

OUT=(OUT.extend(IN))

到

OUT.extend(IN)

或等价

OUT = OUT + IN

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