[List Ops]: def concat(lists) possible test error

[dfreeman500]

Hello,
I'm a relative newbie so hopefully I'm not adding more work.

In the Python List Ops project 'list_ops.py',

def concat(lists): is supposed to "(given a series of lists, combine all items in all lists into one flattened list)".

On line 36 in the test file the expected result does not appear to be a flattened list:
def test_concat_list_of_nested_lists(self): self.assertEqual( concat([[[1], [2]], [[3]], [[]], [[4, 5, 6]]]), [[1], [2], [3], [], [4, 5, 6]], )

I would expect that the test should actually be:

def test_concat_list_of_nested_lists(self): self.assertEqual( concat([[[1], [2]], [[3]], [[]], [[4, 5, 6]]]), [1, 2, 3, 4, 5, 6], )

So, [1, 2, 3, 4, 5, 6] instead of [[1], [2], [3], [], [4, 5, 6]]

Thanks for all you do!

[github-actions]

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[IsaacG]

The prose might benefit from some rewording but this is an intro to lists exercise. There's an explicit and specific exercise for list flattening which is distinct from this exercise.

[BethanyG]

Hi @dfreeman500 👋🏽

Thanks for filing this issue.

We pull the test cases for practice exercises from a common repo, problem specifications and use a test-case generator here on the Python track to turn the canonical data for a given exercise into python unittest/pytest test cases.

Here is the canonical data for List-Ops. As you can see, the expected result treats the innermost lists as elements, and does not unpack them, but does remove the enclosing (second-level) lists. So it does appear the spirit here is "flatten to one" as opposed to "recursively unpack".

With all that being said, I agree that the word "flattened" could be easily mis-interpreted in the instructions, and could benefit from some more detail or explanation.

I'd suggest that you PR a change/start a discussion about the exercise in problem specifications, and perhaps ask about the logic of the expected result for that case. I know in Python that a general default is one level of unpacking, but this is actually two levels, but not a full unpack. We may want to examine how/why that test case is there, and if it needs to be altered and/or the instructions altered.

[BethanyG]

Closing this for now, since the issue lies in problem specifications. Can re-open if an instruction append on the track is needed.