On Tue, 13 Aug 2013 10:11:29 +0200, Stefan Behnel wrote: > Steven D'Aprano, 13.08.2013 08:25: >> On Mon, 12 Aug 2013 13:42:14 +0200, Peter Otten wrote: >>> Steven D'Aprano wrote: >>> >>>> Is it possible to call a Python macro from ctypes? For example, >>>> Python 3.3 introduces some new macros for querying the internal >>>> representation of strings: >>>> >>>> http://www.python.org/dev/peps/pep-0393/#new-api >> [...] >> >>> That's not possible. It may look like a function, but a preprocessor >>> replaces the C macro in the C source before compilation. >> >> That's what I feared. >> >> In that case, how would I use ctypes to access the underlying fields in >> the new string implementation? > > I'd personally use Cython (no surprise here), but in order to use > something like ctypes, which works at the ABI level, not the API level, > and doesn't use a C compiler to get things properly configured for the > local platform, you'd have to manually define the actual PyObject struct > in order to access its fields directly. > > The macros are there to give you source code level portability for that, > but if you start defining the struct layout statically, you're pretty > much on your own when it comes to stuff like different CPython versions, > debug builds, etc. > > Could you describe your use case a little deeper? Maybe there's a better > way all together to do what you want.
One concrete example of what I want to do is introspect Python 3.3 strings. E.g. to tell whether they are 1 byte, 2 byte or 4 byte strings. Strings have a "kind" field, set to 0-3, that specifies how many bytes per char, but it is not exposed to Python. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
