Hi,
I am trying to define a c struct and wrap it in a python object, but
fail to make cython accept my .pyx files.
My intention is to define c structs that are passed to cdefs (for more
efficient function calls) and wrap them in extension types that allow
for greater flexibility and higher level programming.
I use three files:
vector.pxd and vector.pyx define the cdef struct and wrapper extension type
vector_test.pyx defines a variable whose type is the extension type,
extracts the c struct, and attempts an operation on it.
My files contain:
File vector.pxd:
================
cdef struct vector_c:
double x, y, z
cdef class vector:
cdef:
vector_c data
vector_c get_data(self)
================
File vector.pyx
================
cdef class vector:
def __init__(self, double x, double y, double z):
self.data.x = x
self.data.y = y
self.data.z = z
cdef vector_c get_data(vector self):
return self.data
def __getitem__(self, ix):
if ix==0:
return self.data.x
elif ix == 1:
return self.data.y
elif ix == 2:
return self.data.z
else:
raise "Error"
==============================
File vector_test.pyx
==============================
import vector
cimport vector
v = vector.vector(1.0, 1.0, 0.0)
cdef:
vector.vector_c w = (v.get_data())
double x = v[0]
double xx = w.x
print x
print xx
==============================
The first two files can be converted to c-code by issuing "cython
vector.pyx". When running "cython vector_test.pyx", I get the error message
=============================================
Error converting Pyrex file to C:
------------------------------------------------------------
...
import vector
cimport vector
v = vector.vector(1.0, 1.0, 0.0)
cdef:
vector.vector_c w = (v.get_data())
^
------------------------------------------------------------
/home/johan/Work/Elasticity/Program/Python/vector_test.pyx:6:35: Cannot
convert Python object to 'vector_c'
=============================================
I am surprised by this message, as I think that no conversion should be
necessary. When I look at the previously generated vector.c I see that
the function get_data should return a pure c struct and not a PyObject.
Grateful for any help.
/ johan
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