[Numpy-discussion] Subclassing ndarray in Pyrex
Pierre GM
pgmdevlist at gmail.com
Wed Jan 31 06:15:05 CST 2007
I'm still trying to subclass ndarray in Pyrex, without much success so far.
I started to follow Francesc's suggestion
(http://projects.scipy.org/pipermail/numpy-discussion/2007-January/025644.html),
but that doesn't fit what I need: the myarray class Francesc introduced is
just an object, not a subclass of ndarray...
The closest I came to something vaguely running is the following (called
subnd.pyx later on):
#-------------------
from definitions cimport import_array, \
malloc, free, npy_intp, \
PyArray_GETITEM, PyArray_EMPTY, \
ndarray, dtype
# NumPy must be initialized
import_array()
import numpy as _N
cdef class Sub_2(ndarray):
cdef readonly object _info
cdef ndarray __mask
def __new__(self, object shape=None, object dtype=None, object
buffer=None,
object order=None, object infodict={}):
self.__mask = <ndarray>_N.zeros(shape, _N.bool)
self._info = infodict
return
property info:
def __get__(self):
return self._info
def __set__(self, value):
self._info = value
property _mask:
def __get__(self):
return self.__mask
def subarray(obj, info={}):
_obj = <ndarray>_N.asarray(obj)
print "_obj is: %s" % _obj
_internal = Sub_2(shape=_obj.shape, dtype=_obj.dtype)
_internal.flat[:] = _obj.flat[:]
_internal.info = info
return _internal
#----------------------
However, I get a segfault when I try to play with it in Python:
>>> import numpy as N
>>> import subnd
>>> L = N.array([1,2,3]
>>> x = subarray(L)
>>> x
Sub_2([1, 2, 3])
>>> x+1
Sub_2([2, 3, 4])
>>> N.log(x)
crash
So obviously I'm missing something, but what ? Some kind of closure ?
Moreover, I'm a bit disappointed with this method: if I understand correctly
the subtleties of subclassing in pyrex, the ndarray.__new__ is called before
Sub_2.__new__, with the same arguments. As ndarray.__new__ doesn't take
optional arguments, the subclass can't either. That's a bit limiting, I have
to call the constructor function all the time...
I'm completely at loss, here. Any advice/help/suggestions would be more than
welcome.
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