reseting an iterator

Jan jan.plaza at plattsburgh.edu
Wed May 20 20:48:07 CEST 2009


On May 20, 2:35 pm, Jan <jan.pl... at plattsburgh.edu> wrote:

OOPS, I have pressed some keys and the message went out before It was
finished.
Here is the last fragment:

So, one can define iterators by defining a class whose objects have
methods
__iter__ and __next__ -- with this approach it is easy to add some
__reset__
method. But the easiest way to define iterators is by constructing a
generating
function (with yield expressions); this function returns iterators,
although
without __reset__. Another way to define an iterator is to define
callable
and using iter(CALLABLE, SENTINEL) -- the resulting iterator will not
have __reset__.
I do not know how Python is implemented but I believe that
in the last two cases, Python could produce improved iterators with
__reset__
at almost no additional cost.

Jan



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