Steve Juranich wrote: > I'm in the process of writing a few extension types, and there's one > that I'd sort of like to have getitem, setitem, getslice, setslice > functionality for. > > I've been looking through the docs and how things are done in > Objects/listobject.c, and it appears tha there are a couple of ways to > do it and I'd like to get some opinions on what's the best way. > > As I see it, here are my options (please correct me if I'm wrong): > > 1) Register my getitem handler as "__getitem__", my setitem handler as > "__setitem__", etc with my PyMethodDef struct for my new type. > > 2) Give my new type a full-blown sequence interface and stick my > handlers in the PySequenceMethods struct. > > 3) Give my new type a full-blown mapping interface and stick my > handlers in the PyMappingMethods struct. > > I kind of want to shy away from (2) and (3) simply because there's > still a lot of stuff going on inside those Py(Sequence|Mapping)Methods > structs that I don't understand and I don't want to be responsible for > learning right now. But I'm also not sure if it's just as easy as > setting some functions to respond to __getitem__, __getslice__, etc. > > As I'm still new to the world of writing extension modules, any > corrections or clarifications would be greatly appreciated. I've > mostly been using SWIG up to this point, but I've got some code here > where I really care what the Python interface looks like, and SWIG > just won't do what I want it to do (with nested templated classes and > the like). >
1. Define the interface you want; it doesn't have to be a full blown sequence or a full blown mapping -- the main thing is that you know what you want it to do; like what is the input to __getitem__, an index or a key?? 2. Implement it in Python. Write some code that will actually use it. Refine your interface. 3. Make the minimal changes so that it can be compiled by pyrex. Read the C code generated by pyrex. At this stage a masochist woulld say "Oh goodie I know what to do now" and go off and hand code a C extension. A sensible person would send Greg Ewing an appreciative e-mail message and keep the extension in pyrex. HTH, John -- http://mail.python.org/mailman/listinfo/python-list
