Why am I getting “TypeError: 'NoneType' object is not subscriptable” when working with a list in Python?

General Discussions
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1

I’m writing a small math-related Python script, and I ran into this error:

TypeError: ‘NoneType’ object is not subscriptable

Here’s the relevant part of my code:

lista = [v1, v3] lista = list.sort(lista) # I think the issue starts here

a = lista[1] - lista[0]

I’m trying to sort the list and then use the values by index. I later got the same issue when doing:

list = [v2, v4]
list = list.sort(list)
b = list[1] - list[0]

After some debugging, it seems lista (and later list) becomes None, which triggers the error when I try to access an index.

I’d appreciate help understanding why this typeerror: ‘nonetype’ object is not subscriptable happens here, and what the correct way is to sort a list and still use its contents afterward.

2

"I’ve run into this TypeError: ‘NoneType’ object is not subscriptable a few times, and it often happens when using the result of list.sort(), which always returns None. The thing is, list.sort() sorts the list in place and doesn’t return a new list. So, instead of this:

lista = list.sort(lista) # wrong: lista becomes None

You should just do this:

lista.sort() # sorts the list in place

Then you can access the elements normally:

a = lista[1] - lista[0]

Alternatively, if you need a sorted copy but don’t want to modify the original list, use sorted() like this:

sorted_list = sorted(lista)  
a = sorted_list[1] - sorted_list[0]

This will help you avoid the ‘NoneType’ object is not subscriptable error!"

3

I’ve faced this error before too! The problem arises because list.sort() does not return a new sorted list. It sorts in place and returns None. If you try to assign that None back to your variable, that’s when Python complains that you’re trying to subscript None. So, instead of doing this:

list = list.sort(list)

Just call:

list.sort()

This works just fine, and you can safely do:

b = list[1] - list[0]

If you need a sorted copy and don’t want to modify the original list, use:

sorted_copy = sorted(list)  
b = sorted_copy[1] - sorted_copy[0]

By doing this, you’ll avoid the dreaded ‘NoneType’ object is not subscriptable error!

4

Hey! I’ve seen this TypeError: ‘NoneType’ object is not subscriptable pop up a few times too. It usually happens because list.sort() doesn’t return anything, it sorts the list in place and returns None. So when you do this:

lista = list.sort(lista)

lista becomes None, and trying to access lista[1] gives you the error. The correct approach is just calling:

lista.sort() # sorts the list in place, no assignment needed

Then you can safely access elements like:

a = lista[1] - lista[0]

If you need a sorted copy and don’t want to alter the original list, use sorted():


sorted_list = sorted(lista)  
a = sorted_list[1] - sorted_list[0]

By doing this, you won’t encounter the ‘NoneType’ object is not subscriptable error!