[Python-Dev] Pickle alternative in stdlib (Was: On breaking modules into packages)

[Nick Coghlan]

On Thu, Nov 4, 2010 at 4:28 PM, anatoly techtonik <techtonik at gmail.com> wrote:
> On Wed, Nov 3, 2010 at 9:08 PM, Glyph Lefkowitz <glyph at twistedmatrix.com> wrote:
>>
>> This is the strongest reason why I recommend to everyone I know that they
>> not use pickle for storage they'd like to keep working after upgrades [not
>> just of stdlib, but other 3rd party software or their own software]. :)
>>
>> +1.
>> Twisted actually tried to preserve pickle compatibility in the bad old days,
>> but it was impossible.  Pickles should never really be saved to disk unless
>> they contain nothing but lists, ints, strings, and dicts.
>
> But what is alternative in stdlib?
> Don't you think that Python doesn't provide any?

Python 3.2a3+ (py3k:85817, Oct 24 2010, 19:25:28)
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import json
>>> dir(json)
['JSONDecoder', 'JSONEncoder', '__all__', '__author__',
'__builtins__', '__cached__', '__doc__', '__file__', '__name__',
'__package__', '__path__', '__version__', '_default_decoder',
'_default_encoder', 'decoder', 'dump', 'dumps', 'encoder', 'load',
'loads', 'scanner']

pickle gets overspecific in many ways, and hence (despite our best
efforts, and those of third parties) may break when changing Python
versions. Serialising to something more language natural (be it JSON,
YAML, XML or one of the multitude of other state encoding formats out
there) is far more likely to be future proof.

As a tool for communicating between different instances of the *same*
version of Python though, pickle is fine.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia