classification
Title: Pickling and copying exceptions doesn't preserve non-__dict__ attributes
Type: behavior Stage: needs patch
Components: Interpreter Core Versions: Python 3.7, Python 3.6, Python 3.5, Python 2.7
process
Status: open Resolution:
Dependencies: 29998 Superseder:
Assigned To: Nosy List: alexandre.vassalotti, serhiy.storchaka
Priority: normal Keywords:

Created on 2017-04-06 05:59 by serhiy.storchaka, last changed 2017-04-06 05:59 by serhiy.storchaka.

Messages (1)
msg291212 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * (Python committer) Date: 2017-04-06 05:59
Pickling and copying exceptions preserves only __dict__ attributes.

This includes writeable internal fields initialized in constructor:

>>> import pickle, copy
>>> e = StopIteration(12)
>>> e.value = 34
>>> e.value
34
>>> e2 = pickle.loads(pickle.dumps(e, 4))
>>> e2.value
12
>>> e2 = copy.copy(e)
>>> e2.value
12

And __slots__:

>>> class E(Exception): __slots__ = ('x', 'y')
... 
>>> e = E()
>>> e.x = 12
>>> e.x
12
>>> e2 = pickle.loads(pickle.dumps(e, 4))
>>> e2.x
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: x
>>> e2 = copy.copy(e)
>>> e2.x
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: x

__context__, __cause__ and __traceback__ are lost too (see issue29466).

Issue26579 is similar, but resolving it will not resolve this issue since BaseException has its own __reduce__ and __setstate__ implementations.

The solution of this issue will look similar to issue29998, but more complex and general.
History
Date User Action Args
2017-04-06 06:00:00serhiy.storchakasetdependencies: + Pickling and copying ImportError doesn't preserve name and path
2017-04-06 05:59:35serhiy.storchakacreate