Flask-Pydantic 0.0.1

Flask extension for integration with Pydantic library

Flask-Pydantic

Flask extension for integration with the awesome pydantic package with Flask.

Basics

validate decorator validates query and body request parameters and makes them accessible via flask's request variable

parameter type	request attribute name
query	query_params
body	body_params

• Success response status code can be modified via on_success_status parameter of validate decorator.
• response_many parameter set to False enables serialization of multiple models (route function should therefore return iterable of models)
• If validation fails, 400 response is returned with failure explanation.

For more details see in-code docstring or example app.

Usage

Basic example

Simply use validate decorator on route function.

:exclamation: Be aware that @app.route decorator must precede @validate (i. e. @validate must be closer to the function declaration).

from typing import Optional

from flask import Flask, request
from flask_pydantic import validate
from pydantic import BaseModel

app = Flask("flask_pydantic_app")


class QueryModel(BaseModel):
    age: int


class BodyModel(BaseModel):
    name: str
    nickname: Optional[str]


class ResponseModel(BaseModel):
    id: int
    age: int
    name: str
    nickname: Optional[str]


@app.route("/", methods=["POST"])
@validate(body=BodyModel, query=QueryModel)
def post():
    # save model to DB
    id_ = ...

    return ResponseModel(
        id=id_,
        age=request.query_params.age,
        name=request.body_params.name,
        nickname=request.body_params.nickname,
    )

• age query parameter is a required int
  • if none is provided the response contains:

    {
      "validation_error": {
        "query_params": [
          {
            "loc": [
              "age"
            ],
            "msg": "field required",
            "type": "value_error.missing"
          }
        ]
      }
    }
    

    • for incompatible type (e. g. string /?age=not_a_number)

      {
        "validation_error": {
          "query_params": [
            {
              "loc": [
                "age"
              ],
              "msg": "value is not a valid integer",
              "type": "type_error.integer"
            }
          ]
        }
      }
      

• likewise for body parameters
• example call with valid parameters: curl -XPOST http://localhost:5000/?age=20 --data '{"name": "John Doe"}' -H 'Content-Type: application/json'

-> {"id": 2, "age": 20, "name": "John Doe", "nickname": null}

Modify response status code

The default success status code is 200. It can be modified in two ways

• in return statement

# necessary imports, app and models definition
...

@app.route("/", methods=["POST"])
@validate(body=BodyModel, query=QueryModel)
def post():
    return ResponseModel(
            id=id_,
            age=request.query_params.age,
            name=request.body_params.name,
            nickname=request.body_params.nickname,
        ), 201

• in validate decorator

@app.route("/", methods=["POST"])
@validate(body=BodyModel, query=QueryModel, on_success_status=201)
def post():
    ...

TODOs:

• iterable of objects
  • in request body
• header request parameters
• cookie request parameters