New submission from sbt <shibt...@gmail.com>: When pickling a function object, if it cannot be saved as a global the C implementation falls back to using copyreg/__reduce__/__reduce_ex__.
The comment for the changeset which added this fallback claims that it is for compatibility with the Python implementation. See http://hg.python.org/cpython/rev/c6753db9c6af However, the current python implementations do not have any such fallback. This affects both 2.x and 3.x. For example Python 2.7.2 (default, Jun 12 2011, 15:08:59) [MSC v.1500 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> import pickle, cPickle, copy_reg >>> def f(): ... pass ... >>> _f = f >>> del f >>> copy_reg.pickle(type(_f), lambda obj: (str, ("FALLBACK",))) >>> cPickle.dumps(_f) "c__builtin__\nstr\np1\n(S'FALLBACK'\np2\ntp3\nRp4\n." >>> pickle.dumps(_f) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "c:\Python27\lib\pickle.py", line 1374, in dumps Pickler(file, protocol).dump(obj) File "c:\Python27\lib\pickle.py", line 224, in dump self.save(obj) File "c:\Python27\lib\pickle.py", line 286, in save f(self, obj) # Call unbound method with explicit self File "c:\Python27\lib\pickle.py", line 748, in save_global (obj, module, name)) pickle.PicklingError: Can't pickle <function f at 0x0299A470>: it's not found as __main__.f I don't know what should be done. I would be tempted to always fall back to copyreg/__reduce__/__reduce_ex__ when save_global fails (not just for function objects) but that might make error messages less helpful. ---------- components: Library (Lib) messages: 156069 nosy: sbt priority: normal severity: normal status: open title: Difference between pickle implementations for function objects type: behavior versions: Python 2.7, Python 3.3 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue14336> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com