LGTM.
Is out so rarely used with overlap that this issue was never reported by a user?

Incidentally, I don't like that we always make a copy for mode='raise' in np.take/put. It defeats the point of having an out argument, which is to get no-copy performance!

Is there an open ENH issue for this?

The problem with "raise" is that it leaves the output array mutated when an error occurs (but not on the first index). So changing it could be seen as introducing a small issue itself.

Advanced indexing assignment currently has similar issues but will simply allow for such mutation, which is not really ideal in a sense (many paths will check the index first, but not all do IIRC, have to check).

Fixed. I also tweaked the np.take and np.choose docstring to clarify that out gives no performance benefit when clip='raise'.

Also, I notice in np.put that the logic for clip='raise' buffering is a no-op. That is, it looks like the intention was to make np.put buffer if clip='raise', but the clause was inside an if-block that only runs if the input was non-contiguous, so in effect np.put usually runs unbuffered and will clobber the input even on exception.

That code should be cleaned up. My suggestion is to just remove the clip='raise' test and run unbuffered, even though that's a little inconsistent what np.take and np.choose do. The major alternative is to make it buffer for mode='raise' but add a note in the docstring about it. Thoughts?

Hmm, can't say I care much which way we go on that function, both sounds fine to me (or even just leaving it, heh). For similarity with those other functions, I think I would tend slightly towards doing the copy, but contiguous input is probably the most common, so going the other way should actually be the smaller change.
But maybe my enthusiasm on these functions is a bit low anyway ;), I always think of them as solving what indexing already solves.

Thanks, I see, you fixed the documentation, sounds good to me. If nobody else has a comment, I will merge it tomorrow or so.

I guess this was ready to go in. Thanks Allan!