enhancement request: make py3 read/write py2 pickle format

[Steven D'Aprano]

On Thursday 11 June 2015 15:39, Devin Jeanpierre wrote:

>> But I'm not talking about re-inventing what already exists. If I want
>> JSON, I'll use JSON, not spend weeks or months re-writing it from
>> scratch. I can't do this:
>>
>> class MyClass:
>>pass
>>
>> a = MyClass()
>> serialised = repr(a)
>> b = ast.literal_eval(serialised)
>> assert a == b
> 
> I don't understand. You can't do that in JSON, YAML, XML, or protocol
> buffers, either. They only provide a small set of types, comparable to
> (but smaller) than the set of types you get from literal_eval/repr.

Well, what do people do when they want to serialise something like MyClass, 
but have to use (say) JSON rather than pickle?

I'd write a method to export enough information (as JSON) to reconstruct the 
instance, and another method to take that JSON and build an instance. If I'm 
going to do all that, *I would use JSON* rather than try to create my own 
format invented from scratch using only literal_eval.


Although... I suppose if I really wanted to be quick and dirty about it...


py> import ast
py> class MyClass(object): pass
... 
py> a = MyClass()
py> s = repr(a.__dict__)
py> b = object.__new__(MyClass)
py> b.__dict__ = ast.literal_eval(s)
py> b
<__main__.MyClass object at 0xb725218c>


;-)



-- 
Steve