[PYTHON MATRIX-SIG] strange slice behaviour

[tim@lassi.ece.uiuc.edu]

I just recently subscribed to the matrix-sig, so I appologize if this
has gone over allready (I've tried to look over the archive, but its
rather large.) Thanks to everyone for putting Numerical Python
together - it looks great.

I have a 2D array and I slice it, it works fine for non-zero length
slices, but behaves strangely (IMHO) for zero length slices. It works
fine for 1D arrays though...

>>> from Numeric import *
>>> a = array([[1,2,3],[4,5,6],[7,8,9]])
>>> a
1 2 3
4 5 6
7 8 9
>>> a[0:2,1]      # OK
2 5
>>> a[0:1,1]      # OK
2
>>>>>> a[0:0,1]   # This is strange !!!
2 5 8
>>> b = array([1,2,3])
>>> b
1 2 3
>>> b[0:0]        # Oops this breaks the PrettyPrinter

Traceback (innermost last):
  File "<stdin>", line 1, in ?
  File "/usr/local/lib/python/numeric/PrettyPrinter.py", line 28, in
arrayToString
    max_str_len = max(len(str(maximum.reduce(data))),
ArrayError: can't take anything from an empty array
>>>
>>> b[0:0].shape      # This gives what I'd expect.
(0,)


Is this the expected behaviour? If it is, does anyone know of a nice
workaround to get the behaviour I'd expect (i.e., a zero size matrix)?

Thanks,


-- 
	-tim

+--------------------------------------------------------------------+
| Tim Hochberg               Ultrahigh Speed Digital Electronics Lab |
| tim@lassi.ece.uiuc.edu              University of Illinois         |
| http://dogbert.ece.uiuc.edu/~tim         (217) 333-6014            |
+--------------------------------------------------------------------+

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