How do I insert list in nested list

Question

how do I insert list 'lst' into the first possition of the 'n_lst'?

n_lst = [['I', 'dont'], ['know', 'what']]
lst = ['whatever', 'whatever2']

what I need:

[['whatever', 'whatever2'], ['I', 'dont'], ['know', 'what']]

https://docs.python.org/3/library/stdtypes.html#mutable-sequence-types — MattDMo, Oct 08 '20 at 20:23
Please repeat [on topic](https://stackoverflow.com/help/on-topic) and [how to ask](https://stackoverflow.com/help/how-to-ask) from the [intro tour](https://stackoverflow.com/tour). Among other things, we expect you to do appropriate research before posting here. This is already answered in many tutorials on line and in several existing Stack Overflow questions. — Prune, Oct 08 '20 at 20:24

score 0 · Answer 1 · answered Oct 08 '20 at 20:23

0

If you want a new list, you can:

>>> result = [lst] + n_lst
>>> result
[['whatever', 'whatever2'], ['I', 'dont'], ['know', 'what']]

If you need to insert lst inside n_lst

>>> n_lst.insert(0, lst)
>>> n_lst
[['whatever', 'whatever2'], ['I', 'dont'], ['know', 'what']]

answered Oct 08 '20 at 20:23

Joan Puigcerver

the first one works. Thank you. Just the second one: it gives me 'none' Do you know why? – Kateřina Veselá Oct 08 '20 at 20:29
`list.insert(index, element)` does not return anything (it returns `None`). It updates the list. – Joan Puigcerver Oct 08 '20 at 20:34

score 0 · Answer 2 · answered Oct 08 '20 at 20:23

0

You can use list1.insert(index, list2). In your case: n_lst.insert(0, lst).

answered Oct 08 '20 at 20:23

QLR

I tried. It gives me 'none' – Kateřina Veselá Oct 08 '20 at 20:25
@KateřinaVeselá - This is because the `.insert()` function returns `None`. The list is changed in place, so an assignment is not required. – S3DEV Oct 08 '20 at 20:28

score 0 · Answer 3 · answered Oct 08 '20 at 20:23

0

Use insert to do this:

n_lst.insert(0, lst)

answered Oct 08 '20 at 20:23

Darcey BM

3 Answers3