Newbie question, Help needed!
Peter Otten
__peter__ at web.de
Fri Mar 12 16:36:14 EST 2004
Antti Isomursu wrote:
> Ok, this is my problem.
> I have a list, with several items.
> I can move forward in that list using iterator (for example, iter(x)
> and then, it.next()...)
>
> But how can I move backwards?
>>> def reverse(seq):
... for i in xrange(len(seq)-1, -1, -1):
... yield seq[i]
...
>>> for c in reverse("abc"): print c
...
c
b
a
>>> r = reverse(range(5))
>>> r.next()
4
>>> r.next()
3
Python 1.4 will have something similar built in.
Or you iterate over a reversed copy:
for item in alist[::-1]:
# do your stuff
>>> iter(range(5)[::-1]).next()
4
Peter
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