> -----Original Message-----
> From: [EMAIL PROTECTED]
[mailto:python-
> [EMAIL PROTECTED] On Behalf Of Antoon
Pardon
> Sent: Monday, April 23, 2007 7:38 AM
> To: [email protected]
> Subject: Tutorial creates confusion about slices
>
> The following is part of the explanation on slices in the
> tutorial:
>
> The best way to remember how slices work is to think of the indices as
> pointing between characters, with the left edge of the first character
> numbered 0. Then the right edge of the last character of a string of n
> characters has index n, for example:
>
> +---+---+---+---+---+
> | H | e | l | p | A |
> +---+---+---+---+---+
> 0 1 2 3 4 5
> -5 -4 -3 -2 -1
>
> This is all very well with a simple slice like:
>
> "HelpA"[2:4] => "lp"
>
>
> But it give the wrong idea when using the following extended slice:
>
> "HelpA"[4:2:-1] => "Ap"
>
> So this doesn't result in the reverse of the previous expression while
> the explanation above suggest it does.
It makes sense if you recognize that the negative step value also flips
which "side" the index is on.
+---+---+---+---+---+
| H | e | l | p | A |
+---+---+---+---+---+
0 1 2 3 4
-6 -5 -4 -3 -2 -1
---
-Bill Hamilton
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