Mailman 3 June 2021 - capi-sig

New script: add Python 3.10 support to your C extensions without losing Python 3.6 support
by Victor Stinner 07 May '22

07 May '22

Hi, I wrote a new script which adds Python 3.10 support to your C extensions without losing Python 3.6 support: https://github.com/pythoncapi/pythoncapi_compat For example, it replaces "op->ob_type" with "Py_TYPE(op)" and replaces "frame->f_back" with "_PyFrame_GetBackBorrow(frame)". It relies on the pythoncapi_compat.h header file that I wrote to implement Python 3.9 and Python 3.10 on old Python versions. Examples: Py_NewRef() and PyThreadState_GetFrame(). The _PyFrame_GetBackBorrow() function doesn't exist in the Python C API, it's only provided by pythoncapi_compat.h to ease the migration of C extensions. I advise you to replace _PyFrame_GetBackBorrow() (borrowed reference) with PyFrame_GetBack() (strong reference). The PyFrame_GetBack() function was added to Python 3.9 and pythoncapi_compat.h provides it on older Python versions. This project is related to my PEP 620 "Hide implementation details from the C API" which tries to make the C API more abstract to later allow to implement new optimization in CPython and to make other Python implementations like PyPy faster when running C extensions. This project only targets extension modules written in C by using directly the "Python.h" API. I advise you to use Cython or HPy to no longer be bothered with incompatible C API changes at every Python release ;-) * https://cython.org/ * https://hpy.readthedocs.io/ I hope that my script will facilitate migration of C extensions to HPy. Victor -- Night gathers, and now my watch begins. It shall not end until my death.

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ANN: expy 0.6.5 released!
by Yingjie Lan 16 Apr '22

16 Apr '22

EXPY is an express way to extend Python! EXPY provides a way to extend python in an elegant way. For more information and a tutorial, see: http://expy.sourceforge.net/ What's new: 1. Correct treatment of __init__ method. 2. Give warnings of missing Py_INCREF on appropriate special type methods. 3. Documentation update. Cheers, Yingjie

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ANNOUNCE: PyBindGen 0.8
by Gustavo Carneiro 10 Mar '22

10 Mar '22

The other day I released PyBindGen 0.8. Main news is that it features a new experimental header file scanner based on pygccxml (i.e., it's similar to py++ in scope, if not in maturity, but does not use boost.pythonunderneath). == What == PyBindGen is a Python module that is geared to generating C/C++ code that binds a C/C++ library for Python. It does so without extensive use of either C++ templates or C pre-processor macros. It has modular handling of C/C++ types, and can be easily extended with Python plugins. The generated code is almost as clean as what a human programmer would write, and does not depend on any library or header files besides Python itself. == Where == https://launchpad.net/pybindgen/ == NEWS == - Support C++ instance attributes through getter/setter methods - Support functions as methods of C++ classes - Support the PyObject* type - Support unsigned int, C strings (char*) (from Mark Lee) - Add basic support for enum types - New experimental automatic module generator based on C/C++ header file scanner and annotations in comments, using pygccxml - Some bug fixes -- Gustavo J. A. M. Carneiro INESC Porto, Telecommunications and Multimedia Unit "The universe is always one step beyond logic." -- Frank Herbert

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C API equivalent to abc.ABCMeta.register?
by Daniel Stutzbach 02 Mar '22

02 Mar '22

I'm the author of an extension module (blist) that provides a type that fits the MutableSequence API. Is there a canonical way for me to register the type as a MutableSequence from the C API? -- Daniel Stutzbach, Ph.D. President, Stutzbach Enterprises, LLC <http://stutzbachenterprises.com>

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Software Development - Application Development - Game Development
by Gary 10 Jan '22

10 Jan '22

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Mail l8st
by casperssidekick 09 Jul '21

09 Jul '21

Sent from my Verizon, Samsung Galaxy smartphone

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HPy API design for bytes and unicode builders
by Antonio Cuni 18 Jun '21

18 Jun '21

Hi all, at the language summit many people told me that the HPy team should try to communicate more with the CPython developers, so let's try :). In HPy we want to design an API to build bytes/str objects in two steps, to avoid the problem that currently in CPython they are not really immutable. Before making any proposal, I spent quite a lot of time in researching how the current API are used to construct bytes/str objects, and I summarized my results here: https://docs.hpyproject.org/en/latest/misc/str-builder-api.html I think that my survey could be interesting for the people in this ML, independently of HPy. That said, I also opened an issue where to discuss concrete proposals for the HPy API to do that: https://github.com/hpyproject/hpy/issues/214 I would be glad to receive comments and suggestions about that, and especially to know whether I missed some important use case in my analysis. Also, if you think that these kind of mails are off-topic in this ML, please let me know and I'll stop. Antonio

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GC for native extensions
by Joannah Nanjekye 09 Jun '21

09 Jun '21

Hey all, For my research, IBM wrote a tracing GC for CPython and I was trying out some ideas on how we would support the CAPI. I know about handles used in HPy but I felt they can actually incur allocation overhead and use more memory. Instead, I thought of changing the semantics of the union type (PyObject) to not point to internal structures and use a stack for sharing data between Python and C. There can be one push function for each Python type with a direct representation in C: Py_pushInteger for ints, etc. When a C function returns, all values in the stack are returned to Python as the results of the C function. Assuming we can have a way of returning multiple values in Python. Specifically, change typedef struct Object *PyObject; To: typedef unsigned int PyObject; Where now PyObject becomes an index into an internal array that stored all values that had to be given to. This means that when a value is in that array, it would not be collected by Python. When the C function returns its whole array is erased, and the values used by the function are collected. This setup gets us a reliable Union type (PyObject), the garbage collector can also move objects. I think that backward compatibility can easily be implemented using macros. What is some feedback on this approach and am I overconfident of having reasonable backward compatibility? Also, can this experiment uncover any insights that CPython would find useful? -- Best, Joannah Nanjekye *"You think you know when you learn, are more sure when you can write, even more when you can teach, but certain when you can program." Alan J. Perlis*

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