Use python 2 shelf in python 3

Question

I have data stored in a shelf file created with python 2.7

When I try to access the file from python 3.4, I get an error:

>>> import shelve
>         


        

Answer 1

The shelve module uses Python's pickle, which may require a protocol version when being accessed between different versions of Python.

Try supplying protocol version 2:

population = shelve.open('shelved.shelf', protocol=2)

According to the documentation:

Protocol version 2 was introduced in Python 2.3. It provides much more efficient pickling of new-style classes. Refer to PEP 307 for information about improvements brought by protocol 2.

This is most likely the protocol used in the original serialization (or pickling).