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I am starting this pull request to show my implementation, I am looking for feedback and help to follow the procedures. Thank you this is my first contribution to python.
@rhettinger

@lsproule Thanks contributing! You can find more information about the cpython procedures in the developers guide: https://devguide.python.org/. In particular, for this PR you need to create an issue this PR can link to. And in general for additions to cpython a good place to discuss new ideas is https://discuss.python.org/c/ideas/6

From the docstring in your PR it looks like the nwise is (roughly) equivelent to the sliding_window method from more-itertools (see https://more-itertools.readthedocs.io/en/stable/api.html#more_itertools.sliding_window)

Is that correct?

@eendebakpt sliding_window doesn't exist in the itertools module. In the docs, they show you how to implement it using the itertools module. However, since they added pairwise. I thought having a C version of nwise or yes a sliding window, would make some sense. It is functionally equivalent to sliding_window in the more_itertools module, but more_itertools is written in python. This would bring it to the standard library and be written in C.

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so for this clinic input should it be Py_ssize_t? Actually how am I supposed to go about generating the clinic stuff appropriately

https://github.com/lsproule/cpython/blob/874d06821711fe99d8e765d78eca4702ced41c80/Modules/itertoolsmodule.c#L398C1-L409C2

also, can we check my allocations and de-allocations because I want to do this well.

https://github.com/lsproule/cpython/blob/874d06821711fe99d8e765d78eca4702ced41c80/Modules/itertoolsmodule.c#L452C1-L516C2

We haven't decided to add sliding_window() to itertools, so it is premature to submit a PR to add it. When pairwise() was added, there was a deliberate decision NOT to add the general case. The jury is still out on whether this would be a worthwhile itertool. I'm monitoring how people use the more-itertools package to see how it is used and whether it fits in well with the rest of the module.

https://discuss.python.org/t/nwise-itertools/51718

Well, I would like to revisit that. I think more-itertools is great, but I personally would like to have this in the itertools toolbelt especially because we do have pairwise, and it would be nice to revisit. I changed it to a draft instead of a pull request while we discuss it. I want this to be a quality addition. I personally have used it for analyzing data. I think itertools is an amazing module, so not having to reach for a library like more-iterools is nice for me. I like to try to stick to the standard library as much as possible.