Export Pydantic model classes (not instances) to JSON

Question

I understand that Pydantic can export models to JSON, see ref. But in practice, this means instances of a model:

from datetime import datetime
from pydantic import BaseModel


class BarModel(BaseModel):
    whatever: int


class FooBarModel(BaseModel):
    foo: datetime
    bar: BarModel


m = FooBarModel(foo=datetime(2032, 6, 1, 12, 13, 14), bar={'whatever': 123})
print(m.json())
#> {"foo": "2032-06-01T12:13:14", "bar": {"whatever": 123}}

My question is parsing the class itself; so that the class could be understood by other languages, for example JavaScript.

Here is an example of what I'm envisioning:

{BarModel: {
   'whatever': 'int'}
}

{FooBarModel: {
  'foo': 'datetime', 
   'bar': {BarModel: {'whatever': 'int'}}
}

Is this possible using built-in Pydantic functionality?

Answer 1

Pydantic has built-in functionality to generate the JSON Schema of your models. This is a standardised format that other languages will have tooling to deal with. For example, with your definitions, running:

import json
print(json.dumps(FooBarModel.model_json_schema(), indent=2))

would output:

{
  "$defs": {
    "BarModel": {
      "properties": {
        "whatever": {
          "title": "Whatever",
          "type": "integer"
        }
      },
      "required": [
        "whatever"
      ],
      "title": "BarModel",
      "type": "object"
    }
  },
  "properties": {
    "foo": {
      "format": "date-time",
      "title": "Foo",
      "type": "string"
    },
    "bar": {
      "$ref": "#/$defs/BarModel"
    }
  },
  "required": [
    "foo",
    "bar"
  ],
  "title": "FooBarModel",
  "type": "object"
}