Sorry I missed your message the first time around. I suspect you're running into this bug:
http://projects.scipy.org/numpy/ticket/1235 This has been fixed in SVN r7514, (and thus 1.4 pre releases), so it's not a platform difference. The workaround (at the expense of performance, of course) is to cast to a list then cast to a string array. I'm not sure if there's a better (i.e. more performant) workaround. But you could (in your client code) check for the version of Numpy and act accordingly. Mike Dan Yamins wrote: > Really, no idea about this? (Sorry if my original email was unclear.) > > On Sat, Nov 21, 2009 at 3:27 PM, Dan Yamins <dyam...@gmail.com > <mailto:dyam...@gmail.com>> wrote: > > Hi all, > > I'm having some issues casting object arrays to string type, > especially on my Ubuntu installation. (Ubuntu Jaunty, 9.04, with > Numpy v. 1.3.) > > With small arrays, the conversion is just wrong. With large > arrays, there seems to be some memory corruption. Conversion to > int or float (when appropriate) seems to work. > > For instance, here are some examples of errors with small arrays: > > >>> X = numpy.array([13,14],'object') > >>> X.astype('|S2') > array(['13', '\xb2'], > dtype='|S2') > >>> X.astype('int') #conversion to int or float seems to > work fine > array([13, 14]) > >>> X.astype(float) > array([ 13., 14.]) > >>> X = numpy.array(['cat','bat'],'object') > >>> X.astype('|S3') > array(['cat', '\x00ba'], > dtype='|S3') > > Large arrays: > > In [24]: X = numpy.array(['cat','bat']*300000,'object') > In [25]: Y = X.astype('|S3') > *** glibc detected *** /usr/bin/python: munmap_chunk(): invalid > pointer: 0xb7cd5008 *** > > > I do NOT have this problem with Numpy 1.4.0.dev7746, installed on > my OSX 10.5.8 machine. There, everything seems to work fine. > > What's going on? I feel like I've seem some traffic about related > issues on the list before, but I couldn't quite tell from reading > the threads what the "final upshot" of the discussion was ... > Is this something that was fixed in recent NumPy 1.4 releases, or > is something about my Ubuntu vs. OSX installations? Generally > speaking can I / should I be relying on casting from object arrays > to do the "right" (or "intuitive") thing? > > thanks, > Dan > > > ------------------------------------------------------------------------ > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion > -- Michael Droettboom Science Software Branch Operations and Engineering Division Space Telescope Science Institute Operated by AURA for NASA _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
