Ivan Vinogradov wrote: > Hello All, > > this seems like a trivial problem, but I just can't find an elegant > solution neither by myself, nor with google's help. > > I'd like to be able to keep an array representing coordinates for a > system of points. > Since I'd like to operate on each point's coordinates individually, > for speed and ufuncs > numarray fits the bill perfectly, especially since system.coordinates > [4] would return proper vector for a 5th point.
BTW, numpy is replacing numarray, so if you're just getting started, you will probably want to be using numpy. http://numeric.scipy.org > To start, read the coordinates from a text file and add them to our > array one by one. > Here it gets un-elegant and probably wasteful for a large number of > points, by converting the whole array to a list only to use append > method and then convert it back to array(sample code below). Also, > there is potential need to add more points later on. Well, you can accumulate points in a list, and them concatenate them wholesale when you are done. Something like the following (untested): import numpy a1 = ... # some pre-existing array of points f = open('mypoints.txt') newpoints = [] for point in points_from_file(f): newpoints.append(point) f.close() a1 = numpy.vstack((a1, newpoints)) Doing the "a1 = numpy.vstack(...)" for each point is rather slow. numpy arrays do have a .resize() method, but it's not very safe and probably just as slow as doing numpy.vstack() for each new point. Now, you could do a preallocation strategy like lists do internally, but it's probably not worth it. -- Robert Kern [EMAIL PROTECTED] "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
