Samuel Freilich <[email protected]> added the comment:
> A modern solution for this is to define a singledispatch function (with
> implementations for your custom types) and pass it as the `default` parameter
> to the dump functions.
Does that work? I thought the default function only got called for
non-serializable types.
I'm running into the same issue with some code that would like to do round-trip
serialization of a datastructure (which doesn't need 100% generality of
supported values but would like to deal with the existing structure of types).
Dealing with set is easy, for example:
def default(obj): # pass to default parameter of json.dumps
if isinstance(obj, frozenset):
return {'_class': 'set', 'items': list(obj)}
...
def object_hook(obj): # pass to object_hook parameter of json.loads
if obj.get('_class') == 'set':
return set(decoded_dict['items'])
...
But you can't do the equivalent thing for tuple, even if you override
encode/iterencode. It seems like the JSON module is making performance versus
generality tradeoffs, it doesn't make a fresh call to encode/iterencode for
every dict key/value for example. Which is fine, but it would be nice if there
was a mode that allowed getting custom behavior for every type, taking the
performance cost.
----------
nosy: +sfreilich
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Python tracker <[email protected]>
<https://bugs.python.org/issue12657>
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