New submission from Anselm Kruis:
Change 18303391b981 breaks unpickling named tuples pickled by 2.7.3 and 2.7.4.
See closed issue #15535 for the full story. Unfortunately Raymond was wrong,
when he wrote that the addition of __dict__ was a 2.7.4 change. It was added by
changeset 26d5f022eb1a in 2.7.3.
Now 2.7.5 can't unpickle any named tuples pickled by 2.7.3, which is probably
one of the most widely used python versions.
Example:
Pickle a namd tuple using 2.7.3 and unpickle it using 2.7.5.
anselm@Emmy:~$ python2.7
Python 2.7.3 (default, Sep 16 2012, 21:46:37)
[GCC 4.4.5] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import collections
>>> import pickletools
>>> import pickle
>>> N=collections.namedtuple("N","a")
>>> n=N(1)
>>> p=pickle.dumps(n, 2)
>>> p2=pickletools.optimize(p)
>>> pickletools.dis(p2)
0: \x80 PROTO 2
2: c GLOBAL '__main__ N'
14: K BININT1 1
16: \x85 TUPLE1
17: \x81 NEWOBJ
18: c GLOBAL 'collections OrderedDict'
43: ] EMPTY_LIST
44: ] EMPTY_LIST
45: ( MARK
46: U SHORT_BINSTRING 'a'
49: K BININT1 1
51: e APPENDS (MARK at 45)
52: a APPEND
53: \x85 TUPLE1
54: R REDUCE
55: b BUILD
56: . STOP
highest protocol among opcodes = 2
>>> print repr(p2)
'\x80\x02c__main__\nN\nK\x01\x85\x81ccollections\nOrderedDict\n]](U\x01aK\x01ea\x85Rb.'
anselm@Emmy:~/sc/eclipsews/fg2py$ fg2python
Python 2.7.5 (default, May 18 2013, 17:02:17)
[GCC 4.1.2 20080704 (Red Hat 4.1.2-44)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import pickle
>>> import collections
>>> N=collections.namedtuple("N","a")
>>> pickle.loads('\x80\x02c__main__\nN\nK\x01\x85\x81ccollections\nOrderedDict\n]](U\x01aK\x01ea\x85Rb.')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File
"/home/anselm/sc/eclipsews/fg2py/arch/rhel4u4-x86_64/lib/python2.7/pickle.py",
line 1419, in loads
return Unpickler(file).load()
File
"/home/anselm/sc/eclipsews/fg2py/arch/rhel4u4-x86_64/lib/python2.7/pickle.py",
line 895, in load
dispatch[key](self)
File
"/home/anselm/sc/eclipsews/fg2py/arch/rhel4u4-x86_64/lib/python2.7/pickle.py",
line 1261, in load_build
d = inst.__dict__
AttributeError: 'N' object has no attribute '__dict__'
As we can see from the trace back, the problem arises from the pickle op-code
'BUILD'. BUILD requires that the object to be build either has a method
__setstate__ or has an attribute __dict__. Therefore I propose:
- Revert change 18303391b981 and add a __getstate__ method
This is the Python 3 fix for the problem.
or
- Add a method __setstate__:
def __setstate__(self, state):
"""For compatibility with Python 2.7.3 and 2.7.4"""
pass
----------
components: Library (Lib)
messages: 189614
nosy: anselm.kruis, rhettinger
priority: normal
severity: normal
status: open
title: python 2.7.5 fails to unpickle namedtuple pickled by 2.7.3 or 2.7.4
type: behavior
versions: Python 2.7
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue18015>
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