If performance is not critical you could just write your own function for a quick fix, doing something like numpy.array([choices[j][i] for i, j in enumerate([2, 3, 1, 0])])
This 32-array limitation definitely looks weird to me though, doesn't seem to make sense. -=- Olivier 2011/6/16 Ed Schofield <e...@pythoncharmers.com> > Hi all, > > I have been investigation the limitation of the choose() method (and > function) to 32 elements. This is a regression in recent versions of NumPy. > I have tested choose() in the following NumPy versions: > > 1.0.4: fine > 1.1.1: bug > 1.2.1: fine > 1.3.0: bug > 1.4.x: bug > 1.5.x: bug > 1.6.x: bug > Numeric 24.3: fine > > (To run the tests on versions of NumPy prior to 1.4.x I used Python 2.4.3. > For the other tests I used Python 2.7.) > > Here 'bug' means the choose() function has the 32-element limitation. I > have been helping an organization to port a large old Numeric-using codebase > to NumPy, and the choose() limitation in recent NumPy versions is throwing a > spanner in the works. The codebase is currently using both NumPy and Numeric > side-by-side, with Numeric only being used for its choose() function, with a > few dozen lines like this: > > a = numpy.array(Numeric.choose(b, c)) > > Here is a simple example that triggers the bug. It is a simple extension of > the example from the choose() docstring: > > ---------------- > > import numpy as np > > choices = [[0, 1, 2, 3], [10, 11, 12, 13], > [20, 21, 22, 23], [30, 31, 32, 33]] > > np.choose([2, 3, 1, 0], choices * 8) > > ---------------- > > A side note: the exception message (defined in > core/src/multiarray/iterators.c) is also slightly inconsistent with the > actual behaviour: > > Traceback (most recent call last): > File "chooser.py", line 6, in <module> > np.choose([2, 3, 1, 0], choices * 8) > File "/usr/lib64/python2.7/site-packages/numpy/core/fromnumeric.py", line > 277, in choose > return _wrapit(a, 'choose', choices, out=out, mode=mode) > File "/usr/lib64/python2.7/site-packages/numpy/core/fromnumeric.py", line > 37, in _wrapit > result = getattr(asarray(obj),method)(*args, **kwds) > ValueError: Need between 2 and (32) array objects (inclusive). > > The actual behaviour is that choose() passes with 31 objects but fails with > 32 objects, so this should read "exclusive" rather than "inclusive". (And > why the parentheses around 32?) > > Does anyone know what changed between 1.2.1 and 1.3.0 that introduced the > 32-element limitation to choose(), and whether we might be able to lift this > limitation again for future NumPy versions? I have a couple of days to work > on a patch ... if someone can advise me how to approach this. > > Best wishes, > Ed > > > -- > Dr. Edward Schofield > Python Charmers > +61 (0)405 676 229 > http://pythoncharmers.com > > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion > >
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