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Re: Storing instances using jsonpickle

From Ned Batchelder <ned@nedbatchelder.com>
Subject Re: Storing instances using jsonpickle
Date 2014-09-03 22:18 -0400
References <c54f7a2f-cf2c-4ee9-ba8e-a309761c1c6a@googlegroups.com> <mailman.13748.1409777587.18130.python-list@python.org> <46e782a5-b087-4f95-aadb-26e233bf5419@googlegroups.com>
Newsgroups comp.lang.python
Message-ID <mailman.13754.1409797129.18130.python-list@python.org> (permalink)

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On 9/3/14 6:30 PM, Josh English wrote:
> On Wednesday, September 3, 2014 1:53:23 PM UTC-7, Ned Batchelder wrote:
>
>> Pickle (and it looks like jsonpickle) does not invoke the class'
>> __init__ method when it reconstitutes objects.  Your new __init__ is not
>> being run, so new attributes it defines are not being created.
>>
>> This is one of the reasons that people avoid pickle: being completely
>> implicit is very handy, but also fragile.
>>
>
> I seem to remember having this exact same frustration when I used pickle and shelve 15 years ago. I had hoped to have another way around this. I spent over a decade trying to make an XML-based database work, in part because of this limitation.
>
> Some days I get so frustrated I think the only data structure I should ever use is a dictionary.
>
> I suppose to make this sort of thing work, I should look at creating custom json encoders and decoders.
>

Typically, you need to decide explicitly on a serialized representation 
for your data.  Even if it's JSON, you need to decide what that JSON 
looks like.  Then you need to write code that converts the JSON-able 
data structure (dict of lists, whatever) into your object.  Often a 
version number is a good idea so that you have some chance of using old 
data as your code changes.

-- 
Ned Batchelder, http://nedbatchelder.com

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Thread

Storing instances using jsonpickle Josh English <Joshua.R.English@gmail.com> - 2014-09-03 13:32 -0700
  Re: Storing instances using jsonpickle Ned Batchelder <ned@nedbatchelder.com> - 2014-09-03 16:52 -0400
    Re: Storing instances using jsonpickle Josh English <Joshua.R.English@gmail.com> - 2014-09-03 15:30 -0700
      Re: Storing instances using jsonpickle MRAB <python@mrabarnett.plus.com> - 2014-09-04 00:39 +0100
        Re: Storing instances using jsonpickle Denis McMahon <denismfmcmahon@gmail.com> - 2014-09-04 01:11 +0000
      Re: Storing instances using jsonpickle Ned Batchelder <ned@nedbatchelder.com> - 2014-09-03 22:18 -0400
        Re: Storing instances using jsonpickle Sam Raker <sam.raker@gmail.com> - 2014-09-03 21:52 -0700
        Re: Storing instances using jsonpickle Josh English <Joshua.R.English@gmail.com> - 2014-09-15 12:30 -0700
      Re: Storing instances using jsonpickle Chris Angelico <rosuav@gmail.com> - 2014-09-04 15:17 +1000
        Re: Storing instances using jsonpickle Dan Sommers <dan@tombstonezero.net> - 2014-09-05 04:38 +0000
          Re: Storing instances using jsonpickle Chris Angelico <rosuav@gmail.com> - 2014-09-05 15:08 +1000
      Re: Storing instances using jsonpickle MRAB <python@mrabarnett.plus.com> - 2014-09-04 12:07 +0100
      Re: Storing instances using jsonpickle MRAB <python@mrabarnett.plus.com> - 2014-09-05 18:04 +0100
        Re: Storing instances using jsonpickle Marko Rauhamaa <marko@pacujo.net> - 2014-09-05 20:16 +0300
          Re: Storing instances using jsonpickle Ned Batchelder <ned@nedbatchelder.com> - 2014-09-05 13:30 -0400
            Re: Storing instances using jsonpickle Marko Rauhamaa <marko@pacujo.net> - 2014-09-05 21:04 +0300
              Re: Storing instances using jsonpickle Ned Batchelder <ned@nedbatchelder.com> - 2014-09-05 16:50 -0400
                Re: Storing instances using jsonpickle Marko Rauhamaa <marko@pacujo.net> - 2014-09-05 23:57 +0300
          Re: Storing instances using jsonpickle Irmen de Jong <irmen.NOSPAM@xs4all.nl> - 2014-09-06 00:18 +0200
      Re: Storing instances using jsonpickle Chris Angelico <rosuav@gmail.com> - 2014-09-06 10:20 +1000
      Re: Storing instances using jsonpickle MRAB <python@mrabarnett.plus.com> - 2014-09-06 17:32 +0100
      Re: Storing instances using jsonpickle Ned Batchelder <ned@nedbatchelder.com> - 2014-09-06 12:56 -0400
      Re: Storing instances using jsonpickle Terry Reedy <tjreedy@udel.edu> - 2014-09-06 14:27 -0400

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