This pre-PEP proposes enhancing the buffer protocol in Python 3000 to implement the array interface (protocol).
This Wiki will serve as a place to record import points raised during the mailing list discussion.
The buffer protocol allows different Python types to exchange a pointer to a sequence of internal buffers. This functionality is extremely useful for sharing large segments of memory between different high-level objects, but it's too limited and has issues.
- There is the little used "sequence-of-segments" option.
- There is no way for a consumer to tell the protocol-exporting object it is "finished" with its view of the memory and therefore no way for the object to be sure that it can reallocate the pointer to the memory that it owns (the array object reallocating its memory after sharing it with the buffer object led to the infamous buffer-object problem).
- Memory is just a pointer. There is no way to describe what's "in" the memory (float, int, C-structure, etc.)
There is no shape information provided for the memory. But, several array-like Python types could make use of a standard way to describe the shape of the memory (!wxPython, GTK, CVXOPT, PyVox, Audio and Video Libraries, ctypes, NumPy)
- Replace the buffer protocol that allows sharing of a single pointer to memory
Have the protocol define a way to describe what's in the memory location (this should unify what is done now in struct, array, ctypes, and NumPy)
- Have the protocol be able to share information about shape (and striding if any)
- Allow exporting objects to define some function that should be called when the consumer object is "done" with the view.
All that is needed is to create a Python "memory_view" object that can contain all the information needed and be returned when the buffer protocol is called --- when it is garbage-collected, the "bp_release_view" function is called on the exporting object.
This "memory_view" is essentially the old Numeric C-structure (including the fact that the data-format is described by another C-structure).
This object is what the buffer protocol should return.