openapi-schema-pydantic

OpenAPI (v3) specification schema as Pydantic classes.

The naming of the classes follows the schema in OpenAPI specification.

Installation

pip install openapi-schema-pydantic

Try me

from openapi_schema_pydantic import OpenAPI, Info, PathItem, Operation, Response

# Construct OpenAPI by pydantic objects
open_api = OpenAPI(
    info=Info(
        title="My own API",
        version="v0.0.1",
    ),
    paths={
        "/ping": PathItem(
            get=Operation(
                responses={
                    "200": Response(
                        description="pong"
                    )
                }
            )
        )
    },
)
print(open_api.json(by_alias=True, exclude_none=True, indent=2))

Result:

{
  "openapi": "3.0.3",
  "info": {
    "title": "My own API",
    "version": "v0.0.1"
  },
  "servers": [
    {
      "url": "/"
    }
  ],
  "paths": {
    "/ping": {
      "get": {
        "responses": {
          "200": {
            "description": "pong"
          }
        },
        "deprecated": false
      }
    }
  }
}

Take advantage of Pydantic

Pydantic is a great tool, allow you to use object / dict / mixed data for for input.

The following examples give the same OpenAPI result as above:

from openapi_schema_pydantic import OpenAPI, PathItem, Response

# Construct OpenAPI from dict
open_api = OpenAPI.parse_obj({
    "info": {"title": "My own API", "version": "v0.0.1"},
    "paths": {
        "/ping": {
            "get": {"responses": {"200": {"description": "pong"}}}
        }
    },
})

# Construct OpenAPI with mix of dict/object
open_api = OpenAPI.parse_obj({
    "info": {"title": "My own API", "version": "v0.0.1"},
    "paths": {
        "/ping": PathItem(
            get={"responses": {"200": Response(description="pong")}}
        )
    },
})

Use Pydantic classes as schema

• The Schema Object in OpenAPI has definitions and tweaks in JSON Schema, which is hard to comprehend and define a good data class
• Pydantic already has a good way to create JSON schema, let's not re-invent the wheel

The approach to deal with this:

1. Use PydanticSchema objects to represent the Schema in OpenAPI object
2. Invoke construct_open_api_with_schema_class to resolve the JSON schemas and references

from pydantic import BaseModel, Field

from openapi_schema_pydantic import OpenAPI
from openapi_schema_pydantic.util import PydanticSchema, construct_open_api_with_schema_class

def construct_base_open_api() -> OpenAPI:
    return OpenAPI.parse_obj({
        "info": {"title": "My own API", "version": "v0.0.1"},
        "paths": {
            "/ping": {
                "post": {
                    "requestBody": {"content": {"application/json": {
                        "schema": PydanticSchema(schema_class=PingRequest)
                    }}},
                    "responses": {"200": {
                        "description": "pong",
                        "content": {"application/json": {
                            "schema": PydanticSchema(schema_class=PingResponse)
                        }},
                    }},
                }
            }
        },
    })

class PingRequest(BaseModel):
    """Ping Request"""
    req_foo: str = Field(description="foo value of the request")
    req_bar: str = Field(description="bar value of the request")

class PingResponse(BaseModel):
    """Ping response"""
    resp_foo: str = Field(description="foo value of the response")
    resp_bar: str = Field(description="bar value of the response")

open_api = construct_base_open_api()
open_api = construct_open_api_with_schema_class(open_api)

# print the result openapi.json
print(open_api.json(by_alias=True, exclude_none=True, indent=2))

Result:

{
  "openapi": "3.0.3",
  "info": {
    "title": "My own API",
    "version": "v0.0.1"
  },
  "servers": [
    {
      "url": "/"
    }
  ],
  "paths": {
    "/ping": {
      "post": {
        "requestBody": {
          "content": {
            "application/json": {
              "schema": {
                "$ref": "#/components/schemas/PingRequest"
              }
            }
          },
          "required": false
        },
        "responses": {
          "200": {
            "description": "pong",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/PingResponse"
                }
              }
            }
          }
        },
        "deprecated": false
      }
    }
  },
  "components": {
    "schemas": {
      "PingRequest": {
        "title": "PingRequest",
        "required": [
          "req_foo",
          "req_bar"
        ],
        "type": "object",
        "properties": {
          "req_foo": {
            "title": "Req Foo",
            "type": "string",
            "description": "foo value of the request"
          },
          "req_bar": {
            "title": "Req Bar",
            "type": "string",
            "description": "bar value of the request"
          }
        },
        "description": "Ping Request"
      },
      "PingResponse": {
        "title": "PingResponse",
        "required": [
          "resp_foo",
          "resp_bar"
        ],
        "type": "object",
        "properties": {
          "resp_foo": {
            "title": "Resp Foo",
            "type": "string",
            "description": "foo value of the response"
          },
          "resp_bar": {
            "title": "Resp Bar",
            "type": "string",
            "description": "bar value of the response"
          }
        },
        "description": "Ping response"
      }
    }
  }
}

Notes

Use of OpenAPI.json() / OpenAPI.dict()

When using OpenAPI.json() / OpenAPI.dict() function, arguments by_alias=True, exclude_none=True has to be in place. Otherwise the result json will not fit the OpenAPI standard.

# OK
open_api.json(by_alias=True, exclude_none=True, indent=2)

# Not good
open_api.json(indent=2)

More info about field alias:

Non-pydantic schema types

Some schema types are not implemented as pydantic classes. Please refer to the following for more info:

License

MIT License