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pythonpython-3.xpython-2.7picklevalueerror
Aleeee
Aleeee

Reputation: 2023

ValueError: unsupported pickle protocol: 3, python2 pickle can not load the file dumped by python 3 pickle?

I use pickle to dump a file on python 3, and I use pickle to load the file on python 2, the ValueError appears.

So, python 2 pickle can not load the file dumped by python 3 pickle?

If I want it? How to do?

Upvotes: 107

Views: 148978

Answers (2)

Matthias
Matthias

Reputation: 13222

You should write the pickled data with a lower protocol number in Python 3. Python 3 introduced a new protocol with the number 3 (and uses it as default), so switch back to a value of 2 which can be read by Python 2.

Check the protocolparameter in pickle.dump. Your resulting code will look like this.

pickle.dump(your_object, your_file, protocol=2)

There is no protocolparameter in pickle.load because pickle can determine the protocol from the file.

Upvotes: 167

enrico.bacis
enrico.bacis

Reputation: 31484

Pickle uses different protocols to convert your data to a binary stream.

You must specify in python 3 a protocol lower than 3 in order to be able to load the data in python 2. You can specify the protocol parameter when invoking pickle.dump.

Upvotes: 57

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