Not making sense

So I solved this with a solution I found online: def flatlist(array): if array == []: return array if isinstance(array[0], list): return flatlist(array[0]) + flatlist(array[1:]) return array[:1] + flatlist(array[1:])

But I originally had the following code which from my research should have worked, yet it would only append integers and not recursively call the function on a nested list. What am I missing?

def flat_list(array):
    flat = []
    for a in array:
        if type(a) is list:
            flat_list(a)
        else:
            flat.append(a)
    return flat