Flatten a nested list

A list can hold integers and other lists, nested to any depth: [1, [2, 3], [4, [5, 6]]]. Return one flat list of the integers in order: [1, 2, 3, 4, 5, 6].

Recursion fits perfectly. Loop over each item: if it's a list, flatten it and add the results; otherwise it's an integer, so add it directly. Use isinstance(item, list) to tell them apart.

Write flatten(nested): given a list that may contain nested lists of integers (any depth), return a single flat list of the integers, in order. Use recursion.

def flatten(nested):
    # return all the integers, in order, as a flat list
    return nested

Click Run to see the output here.

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Flatten a nested list

Flatten a nested list

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