Francesc Alted <falted <at> pytables.org> writes: > > A Monday 19 May 2008, Glenn escrigué: > > I am working on refining some algorithms to process some spectral > > data I have stored in an h5 file using PyTables. The data is stored > > as an EArray. As I work on my algorithm, I'd like to store > > intermediate computations in the same h5 file. The trouble I am > > having is as follows: > > I create a new EArray to store the intermediate result > > Then I iterate through my data, appending my results to the EArray > > If I then realize I've made a mistake in computing the intermediate > > result, I have to do something like: > > try: > > res = fh.getNode(grp, 'res') > > res.remove() > > except: > > pass > > res = fh.createEArray(grp, 'res', Float32Atom(), (0,512)) > > > > in order to remove the old array so that I can start fresh. This > > seems to be slow and cumbersome. > > Is there any better way to do this? Perhaps a way to tell the EArray > > to start at the beginning again so subsequent append operations > > overwrite old data? > > EArray objects supports data overwriting: > > res[slice] = your_new_data > > So, you can re-write your data until the point you've made the mistake, > and then continue to append. > > If you know the final number of rows on your disk-array, you may find > easy to use a CArray and then use regular assignments to fill it (as if > it were an in-memory array). > > Hope that helps, >
Thank you for the suggestion, but this also seems clumsy, because my routine still needs to parts, one to replace the original values, and then a second to add the new values. Most often, I make an error in the first row or two, so the EArray has one incorrect row that I need to reassign, so it seems like a lot of extra code just to treat the first row or two as a special case. To me, it would be ideal if the indexing notation could be extended to allow res[length_of_growable_dimension] = new_data to be equivalent to res.append(new_data). That is, if you index one beyond the end of the growable dimension, it automatically creates a new row. Thank you again, Glenn ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users
