[SciPy-Dev] Use of `input` in ndimage

[Robert Kern]

On Thu, Jun 19, 2014 at 7:46 PM, Jaime Fernández del Río
<jaime.frio at gmail.com> wrote:
> I submitted a PR
> (https://github.com/scipy/scipy/pull/3745#issuecomment-46590839) to remove
> use of the built-in Python function name `input` from the ndimage module,
> where it is used as the argument name for the input data in almost every
> single function. A full list of functions involved has been pulled by Warren
> on the discussion of that PR.
>
> Warren wisely pointed out that changing the name of an argument changes the
> API, and should therefore not be done lightly, as it could break existing
> user code. One could argue. or at least wish, that, since `input` is
> typically the first argument of the functions involved, and is non-optional,
> calls using it as a keyword argument should be rare. But the potential harm
> is undeniable.
>
> It is ugly and a clear violation of PEP8, but although this kind of things
> are usually an accident waiting to happen, it has also proven harmless so
> far. So for now I have simply closed the PR, letting practicality beat
> purity. And so it will remain, unless the community thinks this special case
> is not special enough to break the rules. Inputs on how to handle the API
> change to minimize impact to users are also welcome.

I don't find the current situation particularly problematic. `input()`
is not a function that is used anywhere in ndimage (indeed, using it
would be a much worse problem than shadowing a builtin), and ndimage
is not so frequently modified that anything like this is actually
likely to cause a problem in the future. I do see that `>>> input =
...` is used in some of the docstring examples; cleaning those up
*would* be worth doing.

-- 
Robert Kern