Whats is the way to clone "independen t" iterator? I can't use tee(),
because I don't know how many "independen t" iterators I need. copy and
deepcopy doesn't work...
--pavel
Jul 13 '08
13  6367 
On 15 Jul., 08:16, Yosifov Pavel <b...@ngs.ruwro te:
cloning of iterators in this manner is bad, more good is to use one,
single list(my_iter) instead of (seehttp://aquagnu.blogspo t.com/2008/07/self-repair-iterator-in-python.html).
This won't work for "big" iterators as mentioned by Peter Otten. With
this recipe you can't even clone generator objects ( which are
iterators ) that produce Fibonaccis in a lazy manner.
Regards, Kay
Kay, can you show example of such generator? ReIter, for example, work
with usual generators.
But for "big" iterator, I think is no any good solutions. IMHO we can
discern 2 types of iterators: re-startable (based on internal Python
objects) and not re-startable (with an external state, side-
effects)...
Best regards, Pavel
On Tue, 15 Jul 2008 19:54:30 -0700, Yosifov Pavel wrote:
Kay, can you show example of such generator? ReIter, for example, work
with usual generators.
But for "big" iterator, I think is no any good solutions. IMHO we can
discern 2 types of iterators: re-startable (based on internal Python
objects) and not re-startable (with an external state, side-
effects)...
Has nothing to do with internal vs. external.
Examples: ``itertools.cou nt(1)``, ``itertools.cyc le(iterable)``, or
def fib():
a, b = 0, 1
while True:
yield a
a, b = b, a + b
Ciao,
Marc 'BlackJack' Rintsch
On 16 ÉÀÌ, 11:32, Marc 'BlackJack' Rintsch <bj_...@gmx.net wrote:
On Tue, 15 Jul 2008 19:54:30 -0700, Yosifov Pavel wrote:
Kay, can you show example of such generator? ReIter, for example, work
with usual generators.
But for "big" iterator, I think is no any good solutions. IMHO we can
discern 2 types of iterators: re-startable (based on internal Python
objects) and not re-startable (with an external state, side-
effects)...
Has nothing to do with internal vs. external.
Examples: ``itertools.cou nt(1)``, ``itertools.cyc le(iterable)``, or
def fib():
a, b = 0, 1
while True:
yield a
a, b = b, a + b
Ciao,
Marc 'BlackJack' Rintsch
Yes. So, I'm disconcerted: what Python "means" about iterators. Why
iterator's are not clonable in default?.. ``itertools.cou nt(it) ``
"suppose" ``it`` will be restarted after count? So ``count(it)``
"suppose" ``it`` is restarable and therefore clonable (why not?!).
Generator is only function, so can be restarted/cloned. Generator
keeps "position" and can't be iterated again. But this position can be
reseted (main rule: if generator function has not side-effects/
external state, see below)!
Iterator, I think, is more general method (for naturally serial
access). For example, you can read values from some device (RS323 or
other) and represent it in program like iterator. In this case,
``__iter__()`` make some preparation, ``next()`` read next value from
RS232. In this case, iterator can't be restarted and really cloned. It
has external state (state of device) and can't to return it at start.
But when series of values are generated (are born) in the program: no
problem to have the feature of clone/restart iterator.
And is very interesting to research Icon iterators. Is possible to
create something in Python such theirs, for non-deterministic solving
purpose... :-)
--pavel This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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