> No, PEP 3149 is about the Python ABI, following PEP 3147,
> which implements this for PYC files.

> The intent is to be able to have mutliple *Python* ABI/API versions
> installed side-by-side, not multiple platform ABI versions :-)

Well, for all practical purposes, the platform *is* part of the ABI :=)

So, if we have been supporting multiple P@P 3147 extension modules since 3.2, I don't see this as a risky change.  I don't think anyone is advocating installing distributions with dozens of extension module variants as a general practice.  But it seems like there are times when it would be useful to have the capability to have more than one and this seems like a safe and logical extension to what PEP 3147 already provides.  I don't have a strong opinion about other platforms.

For OS X, because of the complexity and usefulness of mixing and matching various fat CPU archs and OS X ABIs ("deployment target"), pip already supports selecting the proper wheel to download and wheel creators are tagging with the right metadata to make the right decisions, so I don't think the changes here bring much added value for OS X users, except for two things: (1) we now support PEP 3147 ext file names (which for some reason was never fully implemented on OS X and should have been) which is useful for the original PEP 3147 use cases (for example, if someone wants to distribute non-debug and debug versions of ext modules); (2) the addition of '-darwin' to the PEP 3147 ext file name allows for this additional use case of allowing multiple platform extensions to be stored in the same directory without fear of name clash (even if only one is eventually installed).  I think both are reasonable and safe changes for OS X.