How to flatten a list containing lists and not lists:

Question

Since stackoverflow refuses to let me answer this question as I'm a new user, I'll post my question and answer here. (The question is not present in the list of "Similar questions," either.)

QUESTION:

How can I flatten the following list of lists and ints?

[0, 10, [20, 30], 40, 50, [60, 70, 80]]

Why can't you use any of the MANY answers to the question you linked to? — Scott Hunter, May 02 '22 at 18:02
This question already has plenty of duplicates, it doesn't need yet another. [Flatten an irregular list of lists](https://stackoverflow.com/questions/2158395/flatten-an-irregular-list-of-lists) — Pranav Hosangadi, May 02 '22 at 18:04
@PranavHosangadi You can blame StackOverflow for disallowing me to answer or comment. My answer is different than the others there. No importing. Nothing higher level than fundamental. — It's All Waves, May 02 '22 at 18:08
@ScottHunter because I don't like them. I'm a new coder and I want to avoid importing or using anything I haven't already had a need to learn. That page served as an intro to some higher level stuff for me, but I won't use any of that until I encounter the need multiple times. This is how I learn. — It's All Waves, May 02 '22 at 18:09
What you've linked is an _answer_, not a question. There's no reason you can't answer that question. You can't edit or comment on other people's answers, but there's no reason a new user can't add an answer. If I'm mistaken and new users are indeed prevented from adding answers, then the solution is not to bypass these restrictions by creating a duplicate question. Instead ask a good question that will get you the [reputation](/help/privileges) you need. — Pranav Hosangadi, May 02 '22 at 18:10

Sharim Iqbal · Answer 1 · 2022-05-02T18:15:47.817

1


lst = [0, 10, [20, 30], 40, 50, [60, 70, 80]]

new_lst = []
for a in lst:
    if type(a)!=list:
        new_lst.append(a)
    else:
        new_lst.extend(a)

print(new_lst)

OUTPUT

[0, 10, 20, 30, 40, 50, 60, 70, 80]

Below is working even if the input list also contains float, tuple and string.

lst = [1,2,[3,4],"hello world"]

new_lst = []
for a in lst:
    if isinstance(a,int) or isinstance(a,float) or isinstance(a,str):
        new_lst.append(a)
    else:
        new_lst.extend(a)

print(new_lst)

OUTPUT

[1, 2, 3, 4, 'hello world']

edited May 02 '22 at 18:15

answered May 02 '22 at 18:02

Sharim Iqbal

2,724
1
4
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This list has no `float`s. – Scott Hunter May 02 '22 at 18:05
@ScottHunter I am doing this because if his/her list contains `floats`. – Sharim Iqbal May 02 '22 at 18:07
1

What about when `lst = [1,2,[3,4],"hello world"]`? – Pranav Hosangadi May 02 '22 at 18:13
Also use `isinstance` to check if an object is an instance of a class, not `type() ==` – Pranav Hosangadi May 02 '22 at 18:13

score -1 · Answer 2 · answered May 02 '22 at 18:06

V1 -- works for a list of lists, ints, strings:

def FlattenAllItems(lst):
    if not lst: return []
    flattened = []
    for item in lst:
        if type(item) != list:
            item = [item]
        for i in item:
            flattened.append(i)
    return flattened

V2 -- adds ability to unpack a tuple, as well:

def FlattenAllItems(lst):
    if not lst: return []
    flattened = []
    for item in lst:
        if type(item) == tuple:
            item = [*item]
        if type(item) != list:
            item = [item]
        flattened.extend(item)
    return flattened

Thanks for reading!

How to flatten a list containing lists and not lists:

2 Answers2

Linked