On 4/21/07, Travis Oliphant <[EMAIL PROTECTED]> wrote: > Bill Baxter wrote: > > What's the right way to make a new numpy array that's a copy of some C data? > > > > There doesn't seem to be any API like PyArray_NewFromDescr that > > /copies/ the void*data pointer for you. Do I have to write my own > > loops for this? I can do that, it just seems like it should be a > > library function already, so I'm guessing I'm just overlooking it. > > There seem to be lots of APIs that will wrap pre-existing memory, but > > the ones that allocate for you do not seem to copy. > > > > What do you mean by /copies/ the void * data pointer for you? Do you > mean the API would > > 1) Create new memory for the array > 2) Copy the data from another void * pointer to the memory just created > for the new array? > > If that is what you mean, then you are right there is no such API. I'm > not sure that there needs to be one. It is a two-liner using memcpy.
Yes, I was thinking about memcpy() -- but how about non-contiguous data ? or other non well behaved ndarrays (non-aligned, byte-swapped, ...?) ? > > > A related question -- I'm only trying to copy in order to save myself > > a little hassle regarding how to clean up the allocated chunks. If > > there's some simple way to trigger a particular deallocation function > > to be called at the right time, then that would be the ideal, really. > > > No, there is no place to store that information in NumPy. Either the > ndarray dealloc function frees the memory it created or it doesn't free > any memory. I think the best thing to do in this case would be to > create a memory object wrapping the pointer and then point the ndarray > to it as the source of memory. > Yes, I think one would probably want to create a custom-made python class that provides the memory as buffer or so. This is what you meant - right ? And that class could then define /any/ function to be called once the ref.count goes to zero - right? Could someone with C-API knowledge put a sample together !? This would also be quite useful to be used with a SWIG output typemap. -Sebastian _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
