On Monday 22 January 2007 11:18, Francesc Altet wrote: > You should first inform to Pyrex about the definition of ndarray. For > this, it's only necessary to declare this in a file (say > definitions.pxd):
> from now on, Pyrex knows about the ndarray object and you should be able > to derive a class from it. Note that you should not forget to do a call > to import_array() prior to access the numpy machinery. OK, perfect. Turned out that it was quite silly: I had already two statements inlude 'Python.pxi' include 'numpy.pxi' taken from numpy.random.mtrand, and I was trying to subclass through `numpy.ndarray` when just `ndarray` was what I wanted... Wow, I'm impressed. [about guessing the dtype] > cdef ndarray myvar > myvar = <ndarray>numpy.asarray(obj) That easily ? What's the point of all the PyArray_FROM or _from or _ContiguousFrom implemented in mtrand.numpy.pxi ? I'm afraid I'm missing a point, here... Other example: what's more efficient ? myvar = <ndarray>numpy.empty(shape,dtype) or myvar = PyArray_EMPTY(dims, NPY_TYPE) > > - What'd be a more pyrex-esque way to code the resize and reshape > > functions ? > > Again, just use the python flavor: > > myvar = myvar.reshape((...)) I used that so far and it works nicely, but I wonder whether it was that efficient, hence my question for a more pyrex-esque way. Corollary below. > > - Is there a standard way to deal w/ __getitem__ ? especially when the > > item is not an integer (but a slice or a sequence) ? > > def __getitem__(self, fieldName): > if isinstance(key, int): > ... > elif isinstance(key, slice): > ... > elif isinstance(key, (list, tuple)): OK, I guess a specific example will help me explain myself: One of the issues with the new implementation of MaskedArray is that we overload __getitem__, which slow things down. I just copied the corresponding portion of the python code, namely _data = self._data.__getitem__(index) _mask = self._data.__getitem__(index) pasted it in the .pyx I'm writing, and lo! It works ! But elsewhere in the manual is given the example of a loop using `range`, when one should use some explicit interval, and my understanding was that using python expressions was not as efficient as having more proper C expressions. Is this the case here ? Do I have to reimplement __getitem__ on arrays, or could I just keep on using the current approach ? > Remember, the pyrex manual is your friend. In particular, for object > oriented programmimg with pyrex be sure to have a look at: > > http://www.cosc.canterbury.ac.nz/greg.ewing/python/Pyrex/version/Doc/extens >ion_types.html Ahah ! Some more doc ! I couldn't find the link to it on the pyrex front page... (And obviously, I didn't look close enough in the overview page...) My bad, sorry. Francesc, thanks again. I'll probably contact you very soon off list (and will start thinking about a wiki page) _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
