[Numpy-discussion] Passing a Null pointer after ndarray prototype definition
I have a problem in that I have a DLL function which accepts several numpy double arrays, but you need to pass a NULL pointer for the ones from which you do not require results. The prototype is as follows: T_ndDp = numpy.ctypeslib.ndpointer(dtype=float, ndim=1, flags='C_CONTIGUOUS') Prototype_example = CFUNCTYPE(None, c_long, T_ndDp, T_ndDp, T_ndDp) In ctypes None is equivelent to NULL, though in order to get past the prototype argchecks you need to cast the object to None. If for example the pointer was to a simple double one could write something like: cast(None, POINTER(c_double)) the problem is in casting to None for the above (T_ndDp) type Any help would be greatly appreciated Nicholas ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
[Numpy-discussion] random access iterators
I'm looking at writing some c++ code to interoperate with numpy. A c++ random access iterator must include a 'distance' function. distance (i1, i2) must return the number of times i1 has to be incremented to reach i2. Is there a way to get this from PyArrayIterObject? ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] how do I list all combinations
On Wed, 26 Dec 2007, Mathew Yeates apparently wrote: r1=[dog,cat] r2=[1,2] I want to return [[dog,1],[dog,2],[cat,1],[cat,2]] This is a Cartesian product. Sage has ``cartesian_product_iterator`` for this. Also URL:http://www.sagemath.org/doc/html/ref/module-sage.combinat.cartesian-product.html Here is a Cookbook implementation. URL:http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/302478 The generator may be adequate to your needs. Here is a recursive implementation that does not use multi-dimensional indexing: def set_product(*sets): last_set = sets[-1] drop_last = sets[:-1] if drop_last: result = set( x+(y,) for x in set_product(*drop_last) for y in last_set ) else: result = set( (y,) for y in last_set ) return result Sorry for a late reply. I'm catching up on email... Cheers, Alan Isaac ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] random access iterators
Neal Becker wrote: I'm looking at writing some c++ code to interoperate with numpy. A c++ random access iterator must include a 'distance' function. distance (i1, i2) must return the number of times i1 has to be incremented to reach i2. Is there a way to get this from PyArrayIterObject? In the general case, not directly. However, you may be able to figure something out using the coordinate array that is stored with each iterator. -Travis O. ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
