On Sun, Mar 6, 2011 at 1:10 AM, Skipper Seabold <jsseab...@gmail.com> wrote: > On Sat, Mar 5, 2011 at 9:28 AM, Ralf Gommers > <ralf.gomm...@googlemail.com> wrote: >> On Sat, Mar 5, 2011 at 8:09 AM, Russell E. Owen <ro...@uw.edu> wrote: >>> The page <http://docs.scipy.org/doc/numpy/user/basics.rec.html> >>> >>> gives a good introduction to structured arrays. However, it says nothing >>> about how to set a particular element (all fields at once) from a >>> collection of data. >>> >>> For instance: >>> >>> stArr = numpy.zeros([4,5], dtype=[("pos", float, (2,)), ("rot", float)]) >>> >>> The question is how to set stArr[0]? >>> >>> >From experimentation it appears that you can provide a tuple, but not a >>> list. Hence the following works just fine (and that the tuple can >>> contain a list): >>> strArr[0,0] = ([1.0, 1.1], 2.0) >>> >>> but the following fails: >>> strArr[0,0] = [[1.0, 1.1], 2.0] >>> with an error: >>> TypeError: expected a readable buffer object >>> >>> This is useful information if one is trying to initialize a structured >>> array from a collection of data, such as that returned from a database >>> query. >>> > > I added a bit at the end here, though it is mentioned briefly above. > Feel free to expand. It's a wiki. You just need edit rights. > > http://docs.scipy.org/numpy/docs/numpy.doc.structured_arrays/
Thanks, I'll make sure that goes in for 1.6.0. >> I'm wondering if that's not a bug? If it's intentional then it is >> certainly counterintuitive. >> > > This comes up from time to time. > > http://thread.gmane.org/gmane.comp.python.numeric.general/30793/focus=30793 > > Perhaps an enhancement ticket could be filed? It doesn't sound trivial > to implement. I filed #1758. You can also assign with an array which fails silently, certainly a bug: >>> arr = np.zeros((5,), dtype=[('var1','f8'),('var2','f8')]) >>> arr['var1'] = np.arange(5) >>> arr[0] = (10,20) >>> arr[0] (10.0, 20.0) >>> arr[0] = np.array([10,20]) # no exception, but garbage out >>> arr[0] (4.2439915824246103e-313, 0.0) Ralf _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
