[issue6673] Py3.1 hangs in coroutine and eats up all memory
Changes by Stefan Behnel sco...@users.sourceforge.net: -- status: closed - open ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6673 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6673] Py3.1 hangs in coroutine and eats up all memory
Stefan Behnel sco...@users.sourceforge.net added the comment: Very good argumentation, thanks Nick! I think this is worth being fixed in the 3.1 series. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6673 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6673] Py3.1 hangs in coroutine and eats up all memory
Nick Coghlan ncogh...@gmail.com added the comment: Reopening - this should be rejected by the compiler as a SyntaxError, since it is the comprehension equivalent of writing return Value inside a generator function. Specifically, in 3.x, the equivalent written out code is: while True: def _listcomp(): result = [] for i in range(chunk_size): result.append((yield)) return result # Would trigger SyntaxError! target.send(_listcomp()) As noted in the comment, the compiler would disallow that expansion with a SyntaxError on the marked line, so the comprehension equivalent should be rejected as well. This also applies to dict and set comprehensions. Generator expressions are slightly less clear, since their expanded equivalent would produce legal code: g = ((yield)*(yield) for i in range(1)) next(g) g.send(2) g.send(3) 6 next(g) Traceback (most recent call last): File stdin, line 1, in module StopIteration That first line is roughly equivalent to: def _genexp(): for i in range(1): yield (yield)*(yield) g = _genexp() So the compiler should probably be keeping track of whether it is inside a comprehension or not to decide whether or not to allow yield expressions. -- keywords: +64bit nosy: +ncoghlan resolution: invalid - ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6673 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6673] Py3.1 hangs in coroutine and eats up all memory
Alexandre Vassalotti alexan...@peadrop.com added the comment: Not a bug. The list comprehension in your chunker: while True: target.send([ (yield) for i in range(chunk_size) ]) is equivalent to the following generator in Python 3: while True: def g(): for i in range(chunk_size): yield (yield) target.send(list(g())) This clearly needs not what you want. So, just rewrite your code using for-loop: while True: result = [] for i in range(chunk_size): result.append((yield)) target.send(result) -- nosy: +alexandre.vassalotti resolution: - invalid status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6673 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6673] Py3.1 hangs in coroutine and eats up all memory
New submission from Stefan Behnel sco...@users.sourceforge.net: Here's a simple coroutine that works perfectly in Python 2.6 but seems to let Py3.1 enter an infinite loop that ends up eating all memory. - def printing_sink(): A simple sink that prints the received values. while True: print( (yield) ) def chunker(chunk_size, target): Receives single items and forwards chunks of a fixed size. Usage example: sink = printing_sink() next(sink) cr = chunker(4, sink) next(cr) for i in range(8): ...cr.send(i) [0, 1, 2, 3] [4, 5, 6, 7] cr.close() while True: target.send([ (yield) for i in range(chunk_size) ]) if __name__ == '__main__': import doctest doctest.testmod() - Fails on: Python 3.1 (r31:73572, Jun 28 2009, 21:07:35) [GCC 4.3.2] on linux2 Works on: Python 2.6.2 (r262:71600, Apr 17 2009, 11:29:30) [GCC 4.3.2] on linux2 The problem seems to be the list comprehension. When I replace it with a normal for-loop, it works perfectly. -- components: Interpreter Core messages: 91428 nosy: scoder severity: normal status: open title: Py3.1 hangs in coroutine and eats up all memory type: crash versions: Python 3.1 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6673 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6673] Py3.1 hangs in coroutine and eats up all memory
Georg Brandl ge...@python.org added the comment: Try list(genexp) instead of [listcomp] in 2.x and see what happens... -- nosy: +georg.brandl ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6673 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6673] Py3.1 hangs in coroutine and eats up all memory
Stefan Behnel sco...@users.sourceforge.net added the comment: Hmm, ok, so this is actually an anticipated bug? And I assume this has been discussed before and was decided to get solved by doing... what? Is it documented somewhere why this happens and what one must avoid to not run into this kind of pitfall? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6673 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6673] Py3.1 hangs in coroutine and eats up all memory
Georg Brandl ge...@python.org added the comment: No idea, actually. I just wanted to point out that it is nothing specific to Python 3. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6673 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
