On 2010-02-18 19:28 PM, Mel wrote:
Steven D'Aprano wrote:
On Thu, 18 Feb 2010 17:30:54 -0600, Robert Kern wrote:
> If all you want is a generator that doesn't yield anything, then
> surely there isn't any one-time processing and you don't need the
> comment?
Sure there is. Python doesn't know that nothing gets yielded until it
hits the return statement before the yield. When it calls .next() on the
iterator, the code elided by the comment executes, then the return is
hit, a StopIteration exception is raised, and the iteration is complete.
I don't understand why you care about having *any* code before the
StopIteration. That's like:
def empty():
for x in range(1000):
pass # Spin wheels uselessly
return
yield
What's the point of the wheel spinning? Did I miss something?
I wonder whether it's for some kind of framework with a main loop like
for it in list_of_iterables:
for x in it:
do_this_or_that (x)
where, every once in a while one wants to throw some arbitrary code into the
process, in the form of an empty iterable with side effects.
Yes. That is exactly what the OP said in his original post:
"""
I have some generators that do stuff, then start yielding results. On occasion,
I don't want them to yield anything ever-- they're only really "generators"
because I want to call them /as/ a generator as part of a generalized system.
"""
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
--
http://mail.python.org/mailman/listinfo/python-list
