Make the Python json encoder support Python's new dataclasses

Question

Starting with Python 3.7, there is something called a dataclass:

from dataclasses import dataclass  @dataclass class Foo:     x: str 

However, the following fails:

>>> import json >>> foo = Foo(x="bar") >>> json.dumps(foo) TypeError: Object of type Foo is not JSON serializable 

How can I make json.dumps() encode instances of Foo into json objects?

Answer 1

Much like you can add support to the JSON encoder for datetime objects or Decimals, you can also provide a custom encoder subclass to serialize dataclasses:

import dataclasses, json  class EnhancedJSONEncoder(json.JSONEncoder):         def default(self, o):             if dataclasses.is_dataclass(o):                 return dataclasses.asdict(o)             return super().default(o)  json.dumps(foo, cls=EnhancedJSONEncoder) 

Answer 2

Can't you just use the dataclasses.asdict() function to convert the dataclass to a dict? Something like:

>>> @dataclass ... class Foo: ...     a: int ...     b: int ...      >>> x = Foo(1,2) >>> json.dumps(dataclasses.asdict(x)) '{"a": 1, "b": 2}'