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

Question

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

Answer 1

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

• In python 2 there are 3 different protocols (0, 1, 2) and the default is 0.

• In python 3 there are 5 different protocols (0, 1, 2, 3, 4) and the default is 3.

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.