Mensanator wrote:
On Mar 5, 12:28 pm, Steven D'Aprano <st...@remove-this-
cybersource.com.au> wrote:
On Fri, 05 Mar 2010 18:12:05 +0000, Arnaud Delobelle wrote:
l = range(10)
l
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
l[7::-1]
[7, 6, 5, 4, 3, 2, 1, 0]
[l[i] for i in range(7, -1, -1)]
[7, 6, 5, 4, 3, 2, 1, 0]
Where does the first -1 come from? Slices are supposed to have default
values of 0 and len(seq):
The only way to get a 0 from a reverse range() is to have a bound of
-1.
Not quite. An empty second bound goes all the way to the zero index:
>>> range(9)[2::-1]
[2, 1, 0]
Gary Herron
l[7::1]
[7, 8, 9]
[l[i] for i in range(7, len(l), 1)]
[7, 8, 9]
[l[i] for i in range(7, len(l), -1)]
[]
I don't believe the actual behaviour is documented anywhere.
Well, it's implied. If the stopping bound in a reverse range()
is greater than the starting bound, you get an empty return.
--
Steven
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