If you do not know the size of your array before you finalize it, then you should use lists whenever you can. I just cooked up a short example:
###################################################################### import timeit import numpy as N values = range(10000) def appendArray(values): result = N.array([], dtype="int") for value in values: result = N.append(result, value) return result def appendList(values): result = [] for value in values: result.append(value) return N.array(result) test = timeit.Timer('appendArray(values)', 'from __main__ import appendArray, values') t1 = test.timeit(number=10) test2 = timeit.Timer('appendList(values)', 'from __main__ import appendList, values') t2 = test2.timeit(number=10) print "Total Time with array: " + str(t1) print "Total Time with list: " + str(t2) ##### Result ##### Total Time with array: 2.12951189331 Total Time with list: 0.0469707035741 ######################################################################## #### Hope this helps, MJ -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Adam Mercer Sent: Thursday, October 11, 2007 7:42 AM To: Discussion of Numerical Python Subject: Re: [Numpy-discussion] appending extra items to arrays On 11/10/2007, Robert Kern <[EMAIL PROTECTED]> wrote: > Appending to a list then converting the list to an array is the most > straightforward way to do it. If the performance of this isn't a problem, I > recommend leaving it alone. Thanks, I'll leave it as is - I was just wondering if there was a better way to do it. Cheers Adam _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion