Class JSONFormatter

IPython/core/formatters.py:808–845

A JSON string formatter. To define the callables that compute the JSONable representation of your objects, define a :meth:`_repr_json_` method or use the :meth:`for_type` or :meth:`for_type_by_name` methods to register functions that handle this. The return value of this format

class JSONFormatter(BaseFormatter):
    """A JSON string formatter.

    To define the callables that compute the JSONable representation of
    your objects, define a :meth:`_repr_json_` method or use the :meth:`for_type`
    or :meth:`for_type_by_name` methods to register functions that handle
    this.

    The return value of this formatter should be a JSONable list or dict.
    JSON scalars (None, number, string) are not allowed, only dict or list containers.
    """
    format_type = Unicode('application/json')
    _return_type = (list, dict)

    print_method = ObjectName('_repr_json_')
    
    def _check_return(self, r, obj):
        """Check that a return value is appropriate
        
        Return the value if so, None otherwise, warning if invalid.
        """
        if r is None:
            return
        md = None
        if isinstance(r, tuple):
            # unpack data, metadata tuple for type checking on first element
            r, md = r
        
        # handle deprecated JSON-as-string form from IPython < 3
        if isinstance(r, str):
            warnings.warn("JSON expects JSONable list/dict containers, not JSON strings",
            FormatterWarning)
            r = json.loads(r)
        
        if md is not None:
            # put the tuple back together
            r = (r, md)
        return super(JSONFormatter, self)._check_return(r, obj)


class JavascriptFormatter(BaseFormatter):