Why can't slice use non-int. indices?

Michael Hudson mwh at python.net
Fri Jun 1 14:50:14 CEST 2001


"Ben Wolfson" <wolfson at uchicago.edu> writes:

> In article <3B168CF7.F44777F9 at yahoo.com>, "Paul Winkler"
> <slinkp23 at yahoo.com> wrote:
> 
> > This is on python 2.1.
> > 
> >>>> a = []
> >>>> a[3:4]
> > []
> >>>> a[3.2: 4]
> > Traceback (most recent call last):
> >   File "<stdin>", line 1, in ?
> > TypeError: slice indices must be integers
> 
> For that matter, why doesn't this work?

Because the sq_item & sq_slice methods in the PySequenceMethod struct
in object.h is declared as taking ints rather than PyObject*s.  This
is probably wrong, but it's hard to see how to fix it without breaking
backwards compatibility.

Cheers,
M.

-- 
  GAG: I think this is perfectly normal behaviour for a Vogon. ...
VOGON: That is exactly what you always say.
  GAG: Well, I think that is probably perfectly normal behaviour for a
      psychiatrist. -- The Hitch-Hikers Guide to the Galaxy, Episode 9



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