json_writer(fo: IO, schema: Union[str, List[T], Dict[KT, VT]], records: Iterable[Any], *, write_union_type: bool = True, validator: bool = False, encoder=<class ''>) → None

Write records to fo (stream) according to schema

  • fo – File-like object to write to
  • schema – Writer schema
  • records – Records to write. This is commonly a list of the dictionary representation of the records, but it can be any iterable
  • write_union_type – Determine whether to write the union type in the json message. If this is set to False the output will be clear json. It may however not be decodable back to avro record by json_read.
  • validator – If true, validation will be done on the records
  • encoder – By default the standard AvroJSONEncoder will be used, but a custom one could be passed here


from fastavro import json_writer, parse_schema

schema = {
    'doc': 'A weather reading.',
    'name': 'Weather',
    'namespace': 'test',
    'type': 'record',
    'fields': [
        {'name': 'station', 'type': 'string'},
        {'name': 'time', 'type': 'long'},
        {'name': 'temp', 'type': 'int'},
parsed_schema = parse_schema(schema)

records = [
    {u'station': u'011990-99999', u'temp': 0, u'time': 1433269388},
    {u'station': u'011990-99999', u'temp': 22, u'time': 1433270389},
    {u'station': u'011990-99999', u'temp': -11, u'time': 1433273379},
    {u'station': u'012650-99999', u'temp': 111, u'time': 1433275478},

with open('some-file', 'w') as out:
    json_writer(out, parsed_schema, records)