I don't dare posting this on cython-users because it's a horrible
hack, but it does make a cython class have a dictionary that gets
recognized by python as one to look up attributes in:
The main problem is to convince Cython to compute the offset of a slot
in a type structure.I ended up importing a C macro for that:
#########################
Contents of myheader.h:
#define my_offset(a) (((Py_ssize_t)&(a->__dict__))-((Py_ssize_t)a))
#########################
cdef extern from "myheader.h":
Py_ssize_t my_offset(Test a)
#make sure we can find tp_dictoffset
cdef extern from *:
ctypedef struct PyTypeExtended "PyTypeObject":
Py_ssize_t tp_dictoffset
#definition of class with the appropriate attribute
cdef class Test:
cdef public dict __dict__
def __init__(self):
self.__dict__={}
#initialization function to force the appropriate tp_dictoffset value
#into the relevant PyTypeObject. This should really be happening
#just before cython calls PyType_Ready, but doing it just afterwards
#doesn't seem to cause problems.
def equip_Test_with_dict():
cdef Test t = Test()
(<PyTypeExtended *>(t.__class__)).tp_dictoffset=my_offset(t)
equip_Test_with_dict()
With this loaded, you can do:
sage: t = Test()
sage: t.a = 1000
sage: t.a
1000
which would normally not be possible.
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