Both __init__ and __cinit__ are passed the same arguments, and the former has Python calling conventions. (Also, we use Python's framework to allocate and construct the new object, so there's not a huge amount of flexibility here and working around this would be quite non-trivial).
On Thu, Jun 7, 2012 at 4:32 AM, Dieter Maurer <die...@handshake.de> wrote: > The following cython source leads to a "Cannot convert 'pointer' to Python > object". > > ctypedef void * pointer > > cdef extern from "nonexistant.h": > cdef pointer to_pointer(object) > > cdef class C: > cdef pointer p > > def __cinit__(self, pointer p): self.p = p > > c = C(to_pointer(None)) > > Why does the constructor call tries an implicit conversion to a > Python object even though it gets precisely the type indicated by > its signature? > > > I am working on a binding for "libxmlsec". The behaviour above leads > to an unnatural mapping. Two examples: > > 1. "libxmlsec" has the concept of a key (used for digital signatures or > encryption), naturally mapped onto a "cdef class Key" encapsulating > the xmlsec key pointer. > > "libxmlsec" provides many functions to create keys - naturally mapped > onto class methods used as alternative constructors. > Would "Cython" allow C level parameters for "__cinit__", > they could look like: > > cdef xmlSecKeyPtr xkey = ... some "libxmlsec" key generating function ... > return Key(xkey) > > With the restriction, this must look like: > > cdef Key key > key.xkey = ... some "libxmlsec" key generating function ... > return key > > Not yet too bad, unless the constructor requires C level arguments. > > 2. "libxmlsec" provides a whole bunch of transforms, handled in C code > via a set of so called "TransformId"s. Each "TransformId" is > generated by a function. > > The natural way would like: > > cdef class TransformId: > cdef xmlSecTransformId tid > def __cinit__(self, xmlSecTransformId tid): self.tid = tid > > TransformInclC14N = TransformId(xmlSecTransformInclC14NGetKlass()) > ... for all standard transforms ... > > The restriction forces the introduction of a helper function: > > cdef class TransformId: > cdef xmlSecTransformId tid > > cdef _mkti(xmlSecTransformId tid): > cdef TransformId t = TransformId() > t.tid = tid > return t > > TransformInclC14N = _mkti(xmlSecTransformInclC14NGetKlass()) > ... for all standard transforms ... > > > > > > -- > Dieter > _______________________________________________ > cython-devel mailing list > cython-devel@python.org > http://mail.python.org/mailman/listinfo/cython-devel _______________________________________________ cython-devel mailing list cython-devel@python.org http://mail.python.org/mailman/listinfo/cython-devel
