capi-sig June 2019

capi-sig@python.org

11 participants
6 discussions

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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PyObject_CallOneArg(), ...TwoArgs()
by Jeroen Demeyer 13 Jul '19

13 Jul '19

Hello all, Victor Stinner recently added the function PyObject_CallNoArgs() for calling an object without any arguments, see https://docs.python.org/3.9/c-api/object.html#c.PyObject_CallNoArgs The next obvious question is: should we have PyObject_CallOneArg(), PyObject_CallTwoArgs()? Of course, this cannot continue forever, so I suggest adding the 1 and 2 argument variants which would cover most use cases. Cython has something like that and it becomes very natural to use these functions. The main advantage is that we can implement these variants much more efficiently than the existing PyObject_CallFunction() or PyObject_CallFunctionObjArgs().

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associate lifetime of PyMethodDef[] and PyTypeObject
by Joe Jevnik 16 Jun '19

16 Jun '19

I am trying to use the PEP384 style type-construction with PyType_FromSpec. I couldn't find much documentation on this, so first: is this the expected way to make types going forward? I have always used static objects, but this API is actually very convenient for programatically generated types. As for my actual question: while nested structs like tp_as_number and tp_as_mapping have been broken up such that you just pass Py_nb_add etc., tp_methods still just wants a null-terminated array of PyMethodDef objects. This would be fine, but the resulting PyCFunction objects hold pointers into this array, meaning I must ensure that the array outlives the type. I could put the array in a capsule and assign it to the type, but then if a user deletes the attribute from the type, it will free the memory calling those methods will be a use after free. I could make a metaclass that has room for the array on the type object itself, but it appears that the type object is always allocated with PyType_GenericAlloc(&PyType_type, nmembers) where nmembers is the size of the Py_tp_members slot. Also, even if I could get the space, this would leak an implementation detail into the class hierarchy, which is probably fine but seems messy. One idea I have is to change PyCFunctionObject to hold a PyMethodDef *value* instead of a pointer. I don't think the extra foot print size will affect much, and will lower the total memory usage of a PyCFunctionObject by one pointer. If anything, it avoids a second indirection to find the function's implementation. I wanted to poll this list before working on this to see if this has already been discussed or if I am just doing something wrong. PyCFunctionObject is not part of the limited ABI, so this should be a stable ABI compatible change. We can make this same change in PyType_Ready for statically allocated types.

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capi-sig June 2019