On Wed, 12 Jul 2000, Paul Prescod wrote:
> Python 2.0b1 (#12, Jul 1 2000, 13:14:33)
> Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam
> Copyright 1995-2000 Corporation for National Research Initiatives (CNRI)
> >>> [0,1,2,3,4,5,6,7,8,9,10][0:5:2]
> Traceback (most recent call last):
> File "<stdin>", line 1, in ?
> TypeError: sequence index must be integer
Yeah. At the moment, [:] calls __getslice__ but [::] calls __getitem__
(ick). The list object is getting a call to __getitem__(slice(0, 5, 2))
and __getitem__ wants an integer. I was assuming this would get cleaned
up along with the introduction of [x:y:z]-style range-makers (i recall
Guido posting a suggestion for how to do so a little while back).
Ah, yes: http://www.python.org/pipermail/python-dev/2000-July/012681.html
The issues were
- handling [:] and [::] consistently
- allowing non-integer indices
- letting user-defined objects do their own handling of negative indices
I believe the two possibilities were
__getitem__ gets either an index or a special slice object
__getslice__ is deprecated (when missing, __getitem__ gets the slice args)
and
__getitem__ always gets an index
__getslice__ gets three arguments, all optional, defaulting to None
The latter isn't backward-compatible, but it makes a heckuva lot
more sense.
-- ?!ng
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