Python recursive function is not using argument correctly

Question

Just can not wrap my head why this code would not work:

def list_flatten(a_list):
    for item in a_list:
        if isinstance(item, list):
            list_flatten(item)
        else:
            yield item

print(list(list_flatten([["A"]])))

print(list(list_flatten(["A", ["B"], "C"])))

Expecting:

["A"] and
["A", "B", "C"]

Getting

[] and
["A", "C"]

Side note: Do not want to use chain.from_iterable, because it will breakdown the strings too, like ["123"] might end up ["1","2","3"]

Does this answer your question? Why does my recursive function return None? — MisterMiyagi
– MisterMiyagi, Commented Mar 7, 2022 at 20:31
list_flatten(item) creates a new iterator (a generator), nothin is done with it and it is discarded — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Mar 7, 2022 at 20:32

AKX · Accepted Answer · 2022-03-07 20:26:24Z

3

You're not doing anything with the result of your recursive call.

Change

list_flatten(item)

to

yield from list_flatten(item)

and you should be good to go. (See the docs for yield from.)

answered Mar 7, 2022 at 20:26

AKX

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