New submission from Anand B Pillai: multiprocessing.Manager seems to have an inconsistency in behaviour/documentation or both.
The behaviour inconsistency is documented in the attached test script which should run for both Python2 and Python3. Briefly, multiprocessing.managers.BaseManager class starts a Python subprocess only after a call to its "start" method. Whereas its subclass, multiprocessing.managers.SyncManager does at the time of object creation. This is undocumented and against the base classe's documented behaviour. Also, the SyncManager is more commonly advertised via the facade multiprocessing.Manager() which is again at odds with the BaseManager's interface in that, 1. It takes no arguments (Python2) and different arguments (Python 3). 2. You can't call "start" on it but you can call "start" if you initialize it via multiprocessing.managers.SyncManager directly (!) 3. Even if you can't call a start on it, apparently you can shut it down via a call to "shutdown" 4. When you try to start such a manager you get a strange AssertionError complaining the state is not INITIAL. A better error is required here. Please find the attached file for all the sequence of tests done. Suggested changes are, 1. Fix the inconsistency in documented behaviour between SyncManager and its base class. Either don't start the child process upon object creation or document it. 2. Fix the inconsistency in SyncManager object creation interface and behaviour via "mulitprocessing.Manager()" and directly via "multiprocessing.managers.SyncManager(...)" . One should be able to start both objects cleanly. And the former should also take the address argument. If not document it properly. 3. The AssertionError when trying to start the SyncManager object obtained via a call to "multiprocessing.Manager()" looks like a bug. It should be fixed - otherwise a bette error should be raised and documentation updated. ---------- assignee: docs@python components: Documentation, Library (Lib) files: mp_test.py messages: 238379 nosy: docs@python, pythonhacker priority: normal severity: normal status: open title: Fix documentation for multiprocessing.Manager type: behavior versions: Python 2.7, Python 3.2, Python 3.3, Python 3.4, Python 3.5, Python 3.6 Added file: http://bugs.python.org/file38537/mp_test.py _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue23698> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
