> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:python- > [EMAIL PROTECTED] On Behalf Of Antoon Pardon > Sent: Monday, April 23, 2007 7:38 AM > To: python-list@python.org > 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 -- http://mail.python.org/mailman/listinfo/python-list