Hi, Let me reply to this one by one. The main reason is to do with speed, memory usage, and Python 2. In Python 3 this is not an issue. This is also the reason for the numpy.arange() function, but this one has not been used in relax yet (though calculation speed ups might be possible using this). The problem is that the Python 2 implementation of range() is horribly inefficient as it allocates all memory needed, populates a list object with all the numbers, and then loops over them. xrange() and numpy.arange() do not do this, hence they make calculations in relax much, much faster. This is in a few select places where the memory used is far too much or where the loop is terminated early. If you are not careful with range() in Python 2, you can kill your program by using up all the RAM on the computer. Back ~10 years this was actually quite a problem and it took me a long time to debug and find the fatal range() calls. In Python 3, I have a feeling that xrange() was turned into range() and the old range() was killed. Therefore typing range(10) in the Python 3 prompt gives:
$ python3.2 Python 3.2.3 (default, Oct 1 2012, 22:45:55) [GCC 4.5.2] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> range(10) range(0, 10) >>> So relax should never rely on range() to create a list, as in the future when Python 2 dies, it will not be a list. However: >>> list(range(10)) [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] This behaviour works from Python 1.5 onwards. There should be a lot of information on the web about the reason why xrange() exists. Note that as soon as wxPython supports Python 3 fully, then relax's main target will be Python 3. Regards, Edward On 10 December 2013 12:47, Troels Emtekær Linnet <[email protected]> wrote: > Hi Edward. > > I wonder why range objects in relax by default are created as > xrange objects? > > I think this is related to the error when importing matplotlib. > from pylab import * > > ------- > relax> M31=range(10) > relax> type(M31) > <type 'xrange'> > relax> print M31[:7] > Traceback (most recent call last): > File "<console>", line 1, in <module> > TypeError: sequence index must be integer, not 'slice' > ----- > > Best > Troels > > _______________________________________________ > relax (http://www.nmr-relax.com) > > This is the relax-devel mailing list > [email protected] > > To unsubscribe from this list, get a password > reminder, or change your subscription options, > visit the list information page at > https://mail.gna.org/listinfo/relax-devel > _______________________________________________ relax (http://www.nmr-relax.com) This is the relax-devel mailing list [email protected] To unsubscribe from this list, get a password reminder, or change your subscription options, visit the list information page at https://mail.gna.org/listinfo/relax-devel
