[issue5518] cPickle produces inconsistent output
rb rb-os...@justgohome.co.uk added the comment: Martin, Sorry, I don't follow. I realise that the refcounts will be different; but pickling an object should surely be independent of the refcount as there is no need to include the refcount in the output? What other way (using pickle or not) can I convert a generic immutable Python object to a string to use as a key in external storage? Currently the documentation points out that the output may be different between pickle and cPickle which implies that the output will be consistent for a single module. If pickle is not required to produce consistent output for the same input (and refcount isn't really part of the input in this case; it is a side issue) than can this be documented? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue5518 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue5518] cPickle produces inconsistent output
Benjamin Peterson benja...@python.org added the comment: pickle is designed to provide persistent storage, not create keys for objects. Changes to the format are fine as long as they are compatible. -- nosy: +benjamin.peterson status: pending - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue5518 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue5518] cPickle produces inconsistent output
Martin v. Löwis mar...@v.loewis.de added the comment: Sorry, I don't follow. I realise that the refcounts will be different; but pickling an object should surely be independent of the refcount as there is no need to include the refcount in the output? There certainly is a need to consider the refcount. Else the memo would not work. What other way (using pickle or not) can I convert a generic immutable Python object to a string to use as a key in external storage? You will have to come up with your own serialization function. There are MANY reasons why using a pickle cannot work. For example, in a dictionary, the order of keys is not guaranteed, and might change even though the dictionaries compare equal. Currently the documentation points out that the output may be different between pickle and cPickle which implies that the output will be consistent for a single module. I doesn't imply this at all. The sentence says just what it says: don't be surprised if you pickle the same object with pickle and cPickle, and get different results. If pickle is not required to produce consistent output for the same input (and refcount isn't really part of the input in this case; it is a side issue) than can this be documented? It's certainly possible to document that, yes. Can you propose a specific patch to the documentation? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue5518 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue5518] cPickle produces inconsistent output
Martin v. Löwis mar...@v.loewis.de added the comment: I'm not quite sure why you expect them to be the same. The inputs are different, after all - in one case, you have a Unicode object with a single reference to it (from the tuple), in the second case, you have a Unicode object with many more references: py sys.getrefcount(key[1]) 2 py sys.getrefcount((1,u'foo')[1]) 5 That makes a difference for cPickle. -- nosy: +loewis resolution: - invalid status: open - pending ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue5518 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
