[issue21333] Document recommended exception for objects that shouldn't be pickled
New submission from Stefan Schwarzer: I recently was confused whether to raise a `PicklingError` or `TypeError` in `__getstate__` if objects of my class can't and shouldn't be pickled. [1] Terry Reedy advised I should use `TypeError`. [2] I wonder if the `pickle` module documention should explicitly recommend using `TypeError` if a class wants to say that its objects can't be pickled. What do you think? [1] https://mail.python.org/pipermail/python-list/2014-April/670987.html [2] https://mail.python.org/pipermail/python-list/2014-April/671002.html ---------- assignee: docs@python components: Documentation messages: 217054 nosy: docs@python, sschwarzer priority: normal severity: normal status: open title: Document recommended exception for objects that shouldn't be pickled type: enhancement versions: Python 3.5 _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue21333> _______________________________________
Changes by Berker Peksag <berker.peksag@gmail.com>: ---------- nosy: +alexandre.vassalotti, pitrou _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue21333> _______________________________________
Michael Crouch added the comment: When pickling an object fails on line 70 of copy_reg.py, a "TypeError" is raised. However, according to section 11.1.3 of the Standard Library documentation, when an unpicklable object is passed to the dump() method the "PicklingError" exception will be raised. ---------- components: +Library (Lib) -Documentation nosy: +Michael Crouch versions: +Python 2.7 -Python 3.5 _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue21333> _______________________________________
Serhiy Storchaka added the comment: PicklingError is raised in following cases: 1. Programmical Pickler error (Pickler.__init__() was not called by subclass' __init__()). 2. Due to protocol or implementation limitations: memoizing more than 2**32 objects, saving non-ASCII globals with protocol < 3, etc. Exception type is implementation depended. Sometimes OverflowError or struct.error can be raised instead. 3. When __reduce__/__reduce_ex__ returns invalid value: neither str or tuple, a tuple has wrong size, first tuple element is not a callable, first argument for __newobj__/__newobj_ex__ has no __new__ or doesn't match a type of pickled object, global lookup is failed or doesn't match pickled object, etc. 4. When extension code is not an integer or out of range. ---------- nosy: +serhiy.storchaka _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue21333> _______________________________________
Terry J. Reedy <tjreedy@udel.edu> added the comment: 2.7 docs are no longer revised ---------- nosy: +terry.reedy resolution: -> out of date stage: -> resolved status: open -> closed _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue21333> _______________________________________
participants (5)
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Berker Peksag -
Michael Crouch
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Serhiy Storchaka
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Stefan Schwarzer
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Terry J. Reedy