recursion problem with nested lists in python

Question

I have the following code:

def flat_list(array):
    d=[]
    for i in array:
        if not isinstance(i, list):
            d.append(i)
        else:
            flat_list(i)
    return d

When I call flat_list([1, [2, 2, 2], 4]), I expect it to return unpacked list ([1, 2, 2, 2, 4]). Instead it returns ([1, 4]). Although, if I try (print i) instead of (d.append(i)), it returns unpacked i.

I read an article about recursion, it says return needs to be after base condition.

How do I use kindda (return d.append(i))?

Sayse · Accepted Answer · 2019-10-29 11:58:01Z

2

you call your function, but don't do anything with its return value when calling it recursively

    else:
        d.extend(flat_list(i))

extend will take all the items from the list that flat_list returns, and adds them to your list you are creating within the function

Example

edited Oct 29, 2019 at 11:58

answered Oct 29, 2019 at 11:52

Sayse

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2 Comments

Kamal Valikhanov Over a year ago

I have the same problem using yield. Could you, please, suggest a solution? def flat_list(array): for i in array: if not isinstance(i, list): yield i else: flat_list(i)

Sayse Over a year ago

@KamalValikhanov - You should ask it as a new question with what you've tried and researched

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