On Wed, 14 May 2008 12:25:01 am Guido van Rossum wrote:
> However I see no use for skipping items
> from the start,
You've never had to deal with data where the first N items were special
in some way? e.g. skipping over a header line in a file?
I know I've written code like this before:
it = iter(whatever())
for i in xrange(N): # skip the first N items
it.next()
for item in it:
process(item)
> and if that use case ever came up, passing a slice to
> enumerate() would be the appropriate thing to do.
While slices are wonderfully useful things, they aren't panaceas.
They're not so useful with iterators, and they make a copy of the data,
which can be problematic if there's a *lot* of it.
[tongue firmly in cheek]
Perhaps what we need is a more flexible enumerate function?
enumerate(iterable, start_at_index=0, count_from=0)
Having a consistent index provided by enumerate reduces the amount of
thought I have to put into the loop structure, and avoids the
temptation to do this:
for i, item in enumerate(seq, start=1):
print "line %d: %s" % (i, item)
# subtract one from the index to adjust for one-based counting
seq[i-1] = foo(item)
I never need to think about whether it is zero-based, one-based, or some
other N-based counting, because it is always zero-based.
-0 on any change to enumerate.
--
Steven D'Aprano
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
