[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Changes by Robert Siemer : -- nosy: +siemer ___ Python tracker ___ ___

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Changes by Nick Coghlan ncogh...@gmail.com: -- versions: +Python 3.6 -Python 3.5 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13797 ___ ___

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Changes by Stefan Krah stefan-use...@bytereef.org: -- nosy: -skrah ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13797 ___ ___ Python-bugs-list

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

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[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Changes by Nick Coghlan ncogh...@gmail.com: -- versions: +Python 3.5 -Python 3.4 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13797 ___ ___

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Lenard Lindstrom added the comment: A fourth way to add __getbuffer__ and __releasebuffer__ special methods to a Python class is through a new base class/mixin. The Py_buffer struct pointer passed to __getbuffer__ and __releasebuffer__ is wrapped with another special object type, which

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

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[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

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[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Nick Coghlan ncogh...@gmail.com added the comment: I suggest a PEP for 3.4 as the best way forward for this. -- versions: +Python 3.4 -Python 3.3 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13797

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

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[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Stefan Behnel sco...@users.sourceforge.net added the comment: Ok, just for the record: a single __buffer__() special method with delegation-only semantics would also work for Cython. Taking this path would provide a cleaner separation of the (then delegation-only) Python level protocol and

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Changes by Mark Dickinson dicki...@gmail.com: -- nosy: +mark.dickinson ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13797 ___ ___

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Nick Coghlan ncogh...@gmail.com added the comment: The reason I don't particularly like the delegation only API is that the combination of the new memoryview implementation and bytes/mmap/etc to get a flat region of memory to play with means you could do some quite interesting things entirely

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Alex Gaynor alex.gay...@gmail.com added the comment: FWIW pypy has an __buffer__ method (used exclusively internally, AFAIK), which has semantics similar to your first proposal. -- nosy: +alex ___ Python tracker rep...@bugs.python.org

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Stefan Behnel sco...@users.sourceforge.net added the comment: FWIW, Cython lets user code implement the buffer interface for extension types using the special methods __getbuffer__() and __releasebuffer__(), so providing the same methods (although with a different signature) also for normal

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Stefan Krah stefan-use...@bytereef.org added the comment: I'm trying to understand what you want to be able to write. Do you perhaps have a short example? Also, to get the bigger picture: Is this related to your strview proposal?

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Nick Coghlan ncogh...@gmail.com added the comment: Consider a Python wrapper around a bytes object, or mmap or similar that wants to pass PEP 3118 buffer requests through to the underlying object. Currently, there's no way to write such a delegation - the delegating class has to be written in C.

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Nick Coghlan ncogh...@gmail.com added the comment: To answer your other question, no, strview isn't related - that's strictly a PEP 3118 *consumer*, which is well supported from the Python side now that memoryview is fixed. The trick will be to allow a Python implemented object to be a PEP

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

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[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

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[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Changes by Nick Coghlan ncogh...@gmail.com: -- title: Add a Python level special method to retrieve a PEP 3118 object - Allow objects implemented in pure Python to export PEP 3118 buffers ___ Python tracker rep...@bugs.python.org

[issue13797] Allow objects implemented in pure Python to export PEP 3118 buffers

Nick Coghlan ncogh...@gmail.com added the comment: Reviewing Stefan's work on #10181 suggests to me that option 3 is the only feasible approach. (Allowing memoryview subclasses will permit types to pass their own state between __getbuffer__ and __releasebuffer__) --