s.index(x[, i[, j]]) will change the s ?

[Chris Rebert]

On Wed, Sep 9, 2009 at 10:00 PM, s7v7nislands<s7v7nislands at gmail.com> wrote:
<snip?
> I known index() does not modify the sequence itself. my question is so
> why the doc put the index() method in the mutable sequence types list?

Ah, okay. Now I understand your question. I don't know really. I
suppose it could just as well go under the more general table for
"6.6. Sequence Types". I'd guess it's under Mutable Sequence Types for
convenience's sake since .remove() is mutable-only and makes reference
to the same footnote. You could file a documentation bug:
http://bugs.python.org

<snip>
> When a negative index is passed as the second or third parameter to
> the index() method, the list length is added, as for slice indices.
> I don't understand the mean.  the list length is added, why? if it
> changed, the original will change ?

This feature just lets you use negative list indices, just like with
slicing. For example:

x = ["a", "b", "c", "d"]
assert x[-1] == x[len(x) - 1] == x[3] == "d"
assert x[-2] == x[len(x) - 2] == x[2] == "c"
assert x[-3] == x[len(x) - 3] == x[1] == "b"
assert x[-4] == x[len(x) - 4] == x[0] == "a"

See also tec's examples.

Cheers,
Chris
--
http://blog.rebertia.com