Terry Reedy wrote:
> It makes sense to separate last detection from item processing so last
> detection can be put in a library module and reused.
Here's an extension of your idea that puts the detection of both the first
and the last item into a generator:
def mark_first(items):
items = iter(items)
yield True, next(items)
for item in items:
yield False, item
def mark_last(items):
items = iter(items)
prev = next(items)
for cur in items:
yield False, prev
prev = cur
yield True, prev
def mark_ends(items):
return ((head, tail, item) for head, (tail, item)
in mark_first(mark_last(items)))
for items in "", "a", "ab", "abc":
print list(items), "-->", list(mark_ends(items))
for first, last, item in mark_ends("abc"):
if first:
print "first",
if last:
print "last",
print item
It may not be the most efficient approach, but it looks clean.
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