Unpickling a python 2 object with python 3

I'm wondering if there is a way to load an object that was pickled in Python 2.4, with Python 3.4.

I've been running 2to3 on a large amount of company legacy code to get it up to date.

Having done this, when running the file I get the following error:

      File "H:\fixers - 3.4\addressfixer - 3.4\trunk\lib\address\address_generic.py"
    , line 382, in read_ref_files
        d = pickle.load(open(mshelffile, 'rb'))
    UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 1: ordinal
    not in range(128)

looking at the pickled object in contention, it's a dict in a dict, containing keys and values of type str.

So my question is: Is there a way to load an object, originally pickled in python 2.4, with python 3.4?

You'll have to tell pickle.load() how to convert Python bytestring data to Python 3 strings, or you can tell pickle to leave them as bytes.

The default is to try and decode all string data as ASCII, and that decoding fails. See the pickle.load() documentation:

Optional keyword arguments are _fiximports , encoding and errors , which are used to control compatibility support for pickle stream generated by Python 2. If _fiximports is true, pickle will try to map the old Python 2 names to the new names used in Python 3. The encoding and errors tell pickle how to decode 8-bit string instances pickled by Python 2; these default to ‘ASCII’ and ‘strict’, respectively. The encoding can be ‘bytes’ to read these 8-bit string instances as bytes objects.

Setting the encoding to latin1 allows you to import the data directly:

    with open(mshelffile, 'rb') as f:
        d = pickle.load(f, encoding='latin1')

but you'll need to verify that none of your strings are decoded using the wrong codec; Latin-1 works for any input as it maps the byte values 0-255 to the first 256 Unicode codepoints directly.

The alternative would be to load the data with encoding='bytes', and decode all bytes keys and values afterwards.

From: stackoverflow.com/q/28218466

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