An extension of `partial` itself would indeed be a clean solution (+ backwards compatibility), my concern was just that when most people are still using it in the "traditional" way (for example partializing via keyword), that the additional checks for `SKIP` introduce an unnecessary overhead for those cases. However by checking if `args` contain any placeholder in `__new__` and storing that information in a separate variable it should be possible to keep it to a minimum. Regarding third-party implementations one aspect to consider is compatibility with `partial` itself, i.e. what should happen when further `partial`'izing a previously defined placeholder function (it would need to be a placeholder function again, otherwise the `Ellipsis` or `SKIP` doesn't make much sense).