On Mon, 20 Mar 2017 at 04:28 Serhiy Storchaka <storch...@gmail.com> wrote:
> What is the preferable way of getting the size of tuple, list, bytes, > bytearray: Py_SIZE or PyTuple_GET_SIZE, PyList_GET_SIZE, > PyBytes_GET_SIZE, PyByteArray_GET_SIZE? Are macros for concrete types > more preferable or they are outdated? > > On one hand concrete type macros are longer than Py_SIZE, and since > concrete type macros are defined not for all PyVarObject types we need > to use Py_SIZE for them in any case (for example for PyLongObject and > PyTypeObject). > > On other hand we can add asserts for checking that concrete type macros > are used with correct types. When I wrote a patch that replaces Py_SIZE > with concrete type macros I found two cases of misusing Py_SIZE with > dict object: one in _json.c (already fixed in > 3023ebb43f7607584c3e123aff56e867cb04a418) and other in dictobject.c > (still not fixed). If prefer using concrete type macros this would > unlikely happen. > Personally I have always used the concrete versions when available when it doesn't forcibly constrain the input to the function. In other words I wouldn't force a function to only take a list so I could use PyList_GET_SIZE, but if I'm constructing some internal list object or a function is defined to return a list already then I would just use the concrete versions. But I also wouldn't worry about changing uses of Py_SIZE unless I was already changing the surrounding code. I guess we could clarify this in PEP 7 if it doesn't say when to care about this and once we reach consensus on what we all prefer.
_______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
