Alexander Belopolsky <[email protected]> added the comment:
There seems to be a bug somewhere in 2.x cPickle. Here is a somewhat simpler
way to demonstrate the bug: the following code
from pickletools import dis
import cPickle
t = 1L, # use long for easy 3.x comparison
s1 = cPickle.dumps(t)
s2 = cPickle.dumps(cPickle.loads(s1))
print(s1 == s2)
dis(s1)
dis(s2)
prints
False
0: ( MARK
1: L LONG 1L
5: t TUPLE (MARK at 0)
6: p PUT 1
9: . STOP
highest protocol among opcodes = 0
0: ( MARK
1: L LONG 1L
5: t TUPLE (MARK at 0)
6: . STOP
highest protocol among opcodes = 0
The difference is probably immaterial because nothing in the pickle uses the
tuple again and PUT is redundant, but the difference does not show up when
python pickle module is used instead of cPickle and is not present in py3k.
The comparable py3k code:
from pickletools import dis
import pickle
t = 1,
s1 = pickle.dumps(t, 0)
s2 = pickle.dumps(pickle.loads(s1), 0)
print(s1 == s2)
dis(s1)
dis(s2)
produces
True
0: ( MARK
1: L LONG 1
5: t TUPLE (MARK at 0)
6: p PUT 0
9: . STOP
highest protocol among opcodes = 0
0: ( MARK
1: L LONG 1
5: t TUPLE (MARK at 0)
6: p PUT 0
9: . STOP
highest protocol among opcodes = 0
Most likely the bug is benign and not worth fixing, but I would like to figure
out what's going on and what changed in 3.x.
----------
assignee: -> belopolsky
nosy: +belopolsky
versions: -Python 2.6
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Python tracker <[email protected]>
<http://bugs.python.org/issue8738>
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