This isn't a PEP yet: it's a set of requirements. A PEP eventually needs to say how to implement the requirements, and even at this "proto-PEP" stage, it needs to be plausible that it's implementable. It's on you to explain how your very ambitious requirements can be satisfied in Python. Nobody's going to ask you for an implementation, but references to related tech like HPy and ctypes combined with discussion of how they do or don't meet your requirements would be helpful. 2023-04-23 21:13 に Evan Greenup via Python-ideas さんは書きました:
However there is a lot of limitation in those library [like PyO3].
For good reason. Python does not share data structures with those other languages. CPython's native data structures are a subset of those implemented in C -- obviously, because CPython is implemented in C. But other languages will implement "mutable extensible memory-safe sequence" (ie, Python's list) in different ways (and famously C doesn't provide that!) On the other hand, data structures in other languages may have no built-in equivalent in Python. The low-level cytpes stdlib module provides the flexibility you want, but it's implementation-dependent on the foreign side, and must be.
* The project structure is rigid.
This is a complaint about specific third-party libraries that provide high- level wrapping of a fundamentally low-level facility. I would *expect* the project structure to be rigid. I think you might find it easier to present the proposal convincingly if you "build up" from ctypes, instead of "building down" from PyO3.
* It is really ridiculous when you want to stick some item on the wall. You need to totally redesign this item and manufacture a new item to fit the glue you are going to use.
This is not true of ctypes, which is designed as the thinnest possible wrapper around other languages (specifically C, but to the extent that most C implementations provide facilities for calling FORTRAN and other such languages, it should be possible to extend ctypes to those languages in that way).
As a glue language, Python should be designed to glue other native programming language as a feature of Python programming language itself
As far as I can see this is not feasible, and vastly overemphasizes Python's role as a glue language. Python is a programming language first, and the business of the Python programming language is to be Python. Interfacing to other languages is going to be more or less painful depending on how closely the internals are related, and in general it will be hardware-dependent.
* The interface is universal across all variant and version of Python implementation
It took Microsoft 15 versions and a couple of decades to manage this with just its own runtime library. Remember, not only do Python internals change from version to version, but so do those of other languages. C++ is infamous for incompatibility, in fact. It's hard to imagine that the Python side of the interface can be completely independent of the other language, when the whole point is that the other language has specific features that *Python does not*. As Jelle mentions, a standardized ABI for Python is in process, the current iteration being the HPy project. However AIUI the goal is a consistent ABI across Python versions, not making construction of FFIs easier. All it should do I believe is remove ABI compatibility across Python versions from the set of problems an FFI needs to deal with. That's useful, but doesn't remove any of the complexity caused by different representations in the target language.
It is a lively data structure with in-memory representation, they are unified no matter what Python variant is used and what low level native language is used.
So you're suggesting an intermediate data representation, likely requiring two translations (Python to intermediate and intermediate to target language) each time data is to be transferred from Python to a target language and back. If HPy succeeds then that ABI can be frozen as both the Python ABI and the inter- mediate representation, of course. However, consider the C++ standard template library. In Python, everything is an object, with a consistent handle. Lists and tuples are uniform sequences of handles, dicts are uniform handle-to-handle mappings. That's not so in the C++ template library. The whole point is to provide individual routines optimized to each variant of a data structure based on the template's type variables. It's one-many, not one-one, from the point of view of your proposed FFI ABI. It seems to me that more than Python's internal representation, which changes fairly slowly and is pretty well-documented, the target ABI is more variable, and if the target is as low-level as C there is not going to be one because equivalents of Python structures will be defined per-project rather than for all C libraries.
* This mechanism is transparent to users, there is modules in standard library to support it. [...] This mechanism provide user with maximum flexibility.
That sounds like ctypes to me.
* almost zero-cost abstraction.
What does that mean?
It just make some basic data representation conversion and invoke the method in dynamic library.
Still sounds like ctypes to me. So I come back to the theme: what do you want that ctypes doesn't provide? https://docs.python.org/3/library/ctypes.html