Alex Hayes added the comment: Some background. I'm not actually trying to pickle MappingProxyType, I'm using the schematics [1] library and recently it broke support for pickle [2] and the cause of that is because they are using MappingProxyType [3] internally (when they used to use dict).
The Python docs on MappingProxyType [4] provides an appropriate level of API documentation but what it doesn't cover is when you should or should not use MappingProxyType (understandably, it's most likely a complex answer). However, I imagine that it's being used in schematics because at the bottom of the Python dict documentation [5] it states; > See also types.MappingProxyType can be used to create a read-only view of a > dict. To answer the question "What would be the point of pickling a MappingProxy?" I would probably have to ask, what is the intended use of MappingProxyType? If one was unfamiliar with the way in which pickle and MappingProxyType works I imagine they would think there would be no reason why a "read-only view of a dict" can't be pickled. So I guess my questions now are; 1. Should types.MappingProxyType be pickleable? 2. Should there be some documentation about the intended use of MappingProxyType? I imagine the answer to the first question is "no" given how `__setstate__` works. ---- [1] https://github.com/schematics/schematics [2] https://github.com/schematics/schematics/issues/510 [3] https://github.com/schematics/schematics/pull/511 [4] https://docs.python.org/3/library/types.html#types.MappingProxyType [5] https://docs.python.org/3/library/stdtypes.html#dict ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue31209> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
