[issue12596] cPickle - stored data differ for same dictionary

Alexandre Vassalotti added the comment: There is no guarantee the binary representation of pickled data will be same between different runs. We try to make it mostly consistent when we can, but there are cases, like this one, where we cannot ensure consistency without hurting performance signi

[issue12596] cPickle - stored data differ for same dictionary

Serhiy Storchaka added the comment: Here is a minimal reproducer. Results: pickle.dumps('spam', 2) 0: \x80 PROTO 2 2: USHORT_BINSTRING 'spam' 8: qBINPUT 0 10: .STOP highest protocol among opcodes = 2 pickle.dumps('spam1'[:-1], 2) 0: \x80 PROTO 2

[issue12596] cPickle - stored data differ for same dictionary

Serhiy Storchaka added the comment: It is most probable that the difference is caused by the string interning. -- ___ Python tracker ___ _

[issue12596] cPickle - stored data differ for same dictionary

Ramchandra Apte added the comment: Further proof: here are the results of two invocations of `./python -R -c "import pickle; print(pickle.dumps({'a':1, 'v':1}))"` b'\x80\x03}q\x00(X\x01\x00\x00\x00vq\x01K\x01X\x01\x00\x00\x00aq\x02K\x01u.' b'\x80\x03}q\x00(X\x01\x00\x00\x00aq\x01K\x01X\x01\x00\

[issue12596] cPickle - stored data differ for same dictionary

Ramchandra Apte added the comment: Darn, last sentence has some mistakes. I suspect this issue is happening because the order of a dictionary is different on every run (try repr). -- ___ Python tracker ___

[issue12596] cPickle - stored data differ for same dictionary

Ramchandra Apte added the comment: Try `./python -R -c "import pickle; print(pickle.dumps({'a':1, 'v':1}))" |md5sum`. The output will differ on subsequent run, while trying `./python -R -c "import pickle; print(pickle.dumps({'a':1}))" |md5sum`, the output is always the same. I suspect because

[issue12596] cPickle - stored data differ for same dictionary

Serhiy Storchaka added the comment: It is surprising that the pickled representation of 1-element dict varies from run to run. -- components: +Extension Modules -None ___ Python tracker ___

[issue12596] cPickle - stored data differ for same dictionary

Antoine Pitrou added the comment: As soon as hash randomization is turned on (and it's the default starting with Python 3.3), the pickled representation of dicts will also vary from run to run: $ python -R -c "import pickle; print pickle.dumps({'a':1, 'b':2})" |md5sum c0ae6b7f62b9c0839be883dd1e

[issue12596] cPickle - stored data differ for same dictionary

Changes by Serhiy Storchaka : -- nosy: +serhiy.storchaka stage: -> needs patch ___ Python tracker ___ ___ Python-bugs-list mailing li

[issue12596] cPickle - stored data differ for same dictionary

Philipp Mölders added the comment: The file on disk matters for a replication service, so if a file is touched but not changed it will not be replicated, but in this special case the data change even when the structures have not changed. So if this happens very often it could cause a lot of r

[issue12596] cPickle - stored data differ for same dictionary

R. David Murray added the comment: If the load produces the same result, why does it matter that what is on disk differs? -- nosy: +r.david.murray ___ Python tracker ___ __

[issue12596] cPickle - stored data differ for same dictionary

Changes by Philipp Mölders : -- type: -> behavior ___ Python tracker ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.

[issue12596] cPickle - stored data differ for same dictionary

New submission from Philipp Mölders : I think there is a problem within cPickle. I wanted to store a dictionary with only one entry with cPickle.dump() this works fine and can be loaded with cPickle.load(). But if you store the loaded data with cPickle.dump() again, the stored data differ from