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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