[issue3842] can't run close through itertools.chain on inner generator
Amaury Forgeot d'Arc [EMAIL PROTECTED] added the comment: You somehow must tell the iterator that you are done with it. This is best done by a del c in your first snippet, since c is the last reference to the iterator. To do this in a function (or a context manager), the trick is to wrap the map() iterator inside a generator function. def wrapiterator(it): for x in it: yield x Then your sample becomes: with closing(wrapiterator(chain.from_iterable( ... map(gen, (1,2,3) as c: ...next(c) Which of course can be rewritten as: def closingiterator(it): def wrapper(): for x in it: yield x return closing(wrapper()) with closingiterator(chain.from_iterable(map(gen, (1,2,3) as c: ...next(c) This works because the only reference to the map() iterator is held by the wrapper generator function. Calling its close() method will terminate the function, delete its locals, ultimately call the deallocator of the gen() iterator, which will fire the finally block. Your proposal implies that all c-based iterators need to grow a close method. This is not practical, and is best simulated with this wrapper generator: close()ing the wrapper will (recursively) destroy the iterators. If this also works for you, I suggest to close this issue. -- nosy: +amaury.forgeotdarc resolution: - works for me status: open - pending ___ Python tracker [EMAIL PROTECTED] http://bugs.python.org/issue3842 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3842] can't run close through itertools.chain on inner generator
Raymond Hettinger [EMAIL PROTECTED] added the comment: Sorry, am going to reject this. The use cases are somewhat uncommon and I don't want to clutter-up tools that need to remain as simple as possible. The pure python code for chain() is so simple that it's not hard to roll your own version as needed. -- resolution: works for me - rejected status: pending - closed ___ Python tracker [EMAIL PROTECTED] http://bugs.python.org/issue3842 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3842] can't run close through itertools.chain on inner generator
New submission from Bruce Frederiksen [EMAIL PROTECTED]: There is no way to get generators to clean up (run their 'finally' clause) when used as an inner iterable to chain: def gen(n): ... try: ... # do stuff yielding values ... finally: ... # clean up c = chain.from_iterable(map(gen, (1,2,3))) next(c) 0 # done with c, but can't clean up inner gen! Could you add a 'close' method to itertools.chain that would call close (if present) on both the inner and other iterable? Then clean up could be done as: with closing(chain.from_iterable(map(gen, (1,2,3 as c: ...next(c) # generator finalized by with closing! -- components: Extension Modules messages: 73052 nosy: dangyogi severity: normal status: open title: can't run close through itertools.chain on inner generator type: feature request versions: Python 3.0 ___ Python tracker [EMAIL PROTECTED] http://bugs.python.org/issue3842 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue3842] can't run close through itertools.chain on inner generator
Changes by Benjamin Peterson [EMAIL PROTECTED]: -- assignee: - rhettinger nosy: +rhettinger versions: +Python 2.7, Python 3.1 -Python 3.0 ___ Python tracker [EMAIL PROTECTED] http://bugs.python.org/issue3842 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
