CODEWITHSUNDEEP
pythonjson
Carson
Carson

Reputation: 17751

Python's JSON module doesn't use __get__?

When I serialize a list of objects with a custom __get__ method, __get__ is not called and the raw (unprocessed by custom __get__) value from __set__ is used. How does Python's json module iterate over an item?

Note: if I iterate over the list before serializing, the correct value returned by __get__ is used.

Upvotes: 1

Views: 219

Answers (2)

Dustin
Dustin

Reputation: 1966

From the Python 3.1.2 documentation (re-formatted for viewing here but otherwise unedited):

json.dump(obj, fp, skipkeys=False, ensure_ascii=True, check_circular=True,
          allow_nan=True, cls=None, indent=None, separators=None,
          default=None, **kw)

default(obj) is a function that should return a serializable version of obj or raise TypeError. The default simply raises TypeError.

So your __get__ function should be passed as default=yourcustomjsonencoder.__get__ or something like that? Just a thought. I could be way off (and probably am), but it's an idea at least.

Upvotes: 0

MattH
MattH

Reputation: 38247

It checks whether the object is certain values, or isinstances of list, tuple, or dicts...

It provides a method for what to do if all this fails, and documents how to do this:


import simplejson
class IterEncoder(simplejson.JSONEncoder):
  def default(self, o):
    try:
      iterable = iter(o)
    except TypeError:
      pass
    else:
      return list(iterable)
    return simplejson.JSONEncoder.default(self, o)

simplejson.dumps(YourObject,cls=IterEncoder)

Upvotes: 1

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