Quick start

This guide assumes you have a working understanding of Flask, and that you have already installed both Flask and Flask-RESTX. If not, then follow the steps in the Installation section.

Migrate from Flask-RESTPlus

Warning

The migration commands provided below are for illustration purposes. You may need to adapt them to properly fit your needs. We also recommend you make a backup of your project prior running them.

At this point, Flask-RESTX remains 100% compatible with Flask-RESTPlus’ API. All you need to do is update your requirements to use Flask-RESTX instead of Flask-RESTPlus. Then you need to update all your imports. This can be done using something like:

::
find . -type f -name “*.py” | xargs sed -i “s/flask_restplus/flask_restx/g”

Finally, you will need to update your configuration options (described here). Example:

::
find . -type f -name “*.py” | xargs sed -i “s/RESTPLUS_/RESTX_/g”

Initialization

As every other extension, you can initialize it with an application object:

from flask import Flask
from flask_restx import Api

app = Flask(__name__)
api = Api(app)

or lazily with the factory pattern:

from flask import Flask
from flask_restx import Api

api = Api()

app = Flask(__name__)
api.init_app(app)

A Minimal API

A minimal Flask-RESTX API looks like this:

from flask import Flask
from flask_restx import Resource, Api

app = Flask(__name__)
api = Api(app)

@api.route('/hello')
class HelloWorld(Resource):
    def get(self):
        return {'hello': 'world'}

if __name__ == '__main__':
    app.run(debug=True)

Save this as api.py and run it using your Python interpreter. Note that we’ve enabled Flask debugging mode to provide code reloading and better error messages.

$ python api.py
* Running on http://127.0.0.1:5000/
* Restarting with reloader

Warning

Debug mode should never be used in a production environment!

Now open up a new prompt to test out your API using curl:

$ curl http://127.0.0.1:5000/hello
{"hello": "world"}

You can also use the automatic documentation on you API root (by default). In this case: http://127.0.0.1:5000/. See Swagger UI for a complete documentation on the automatic documentation.

Resourceful Routing

The main building block provided by Flask-RESTX are resources. Resources are built on top of Flask pluggable views, giving you easy access to multiple HTTP methods just by defining methods on your resource. A basic CRUD resource for a todo application (of course) looks like this:

from flask import Flask, request
from flask_restx import Resource, Api

app = Flask(__name__)
api = Api(app)

todos = {}

@api.route('/<string:todo_id>')
class TodoSimple(Resource):
    def get(self, todo_id):
        return {todo_id: todos[todo_id]}

    def put(self, todo_id):
        todos[todo_id] = request.form['data']
        return {todo_id: todos[todo_id]}

if __name__ == '__main__':
    app.run(debug=True)

You can try it like this:

$ curl http://localhost:5000/todo1 -d "data=Remember the milk" -X PUT
{"todo1": "Remember the milk"}
$ curl http://localhost:5000/todo1
{"todo1": "Remember the milk"}
$ curl http://localhost:5000/todo2 -d "data=Change my brakepads" -X PUT
{"todo2": "Change my brakepads"}
$ curl http://localhost:5000/todo2
{"todo2": "Change my brakepads"}

Or from python if you have the Requests library installed:

>>> from requests import put, get
>>> put('http://localhost:5000/todo1', data={'data': 'Remember the milk'}).json()
{u'todo1': u'Remember the milk'}
>>> get('http://localhost:5000/todo1').json()
{u'todo1': u'Remember the milk'}
>>> put('http://localhost:5000/todo2', data={'data': 'Change my brakepads'}).json()
{u'todo2': u'Change my brakepads'}
>>> get('http://localhost:5000/todo2').json()
{u'todo2': u'Change my brakepads'}

Flask-RESTX understands multiple kinds of return values from view methods. Similar to Flask, you can return any iterable and it will be converted into a response, including raw Flask response objects. Flask-RESTX also support setting the response code and response headers using multiple return values, as shown below:

class Todo1(Resource):
    def get(self):
        # Default to 200 OK
        return {'task': 'Hello world'}

class Todo2(Resource):
    def get(self):
        # Set the response code to 201
        return {'task': 'Hello world'}, 201

class Todo3(Resource):
    def get(self):
        # Set the response code to 201 and return custom headers
        return {'task': 'Hello world'}, 201, {'Etag': 'some-opaque-string'}

Endpoints

Many times in an API, your resource will have multiple URLs. You can pass multiple URLs to the add_resource() method or to the route() decorator, both on the Api object. Each one will be routed to your Resource:

api.add_resource(HelloWorld, '/hello', '/world')

# or

@api.route('/hello', '/world')
class HelloWorld(Resource):
    pass

You can also match parts of the path as variables to your resource methods.

api.add_resource(Todo, '/todo/<int:todo_id>', endpoint='todo_ep')

# or

@api.route('/todo/<int:todo_id>', endpoint='todo_ep')
class HelloWorld(Resource):
    pass

Note

If a request does not match any of your application’s endpoints, Flask-RESTX will return a 404 error message with suggestions of other endpoints that closely match the requested endpoint. This can be disabled by setting ERROR_404_HELP to False in your application config.

Argument Parsing

While Flask provides easy access to request data (i.e. querystring or POST form encoded data), it’s still a pain to validate form data. Flask-RESTX has built-in support for request data validation using a library similar to argparse.

from flask_restx import reqparse

parser = reqparse.RequestParser()
parser.add_argument('rate', type=int, help='Rate to charge for this resource')
args = parser.parse_args()

Note

Unlike the argparse module, parse_args() returns a Python dictionary instead of a custom data structure.

Using the RequestParser class also gives you sane error messages for free. If an argument fails to pass validation, Flask-RESTX will respond with a 400 Bad Request and a response highlighting the error.

$ curl -d 'rate=foo' http://127.0.0.1:5000/todos
{'status': 400, 'message': 'foo cannot be converted to int'}

The inputs module provides a number of included common conversion functions such as date() and url().

Calling parse_args() with strict=True ensures that an error is thrown if the request includes arguments your parser does not define.

args = parser.parse_args(strict=True)

Data Formatting

By default, all fields in your return iterable will be rendered as-is. While this works great when you’re just dealing with Python data structures, it can become very frustrating when working with objects. To solve this problem, Flask-RESTX provides the fields module and the marshal_with() decorator. Similar to the Django ORM and WTForm, you use the fields module to describe the structure of your response.

from flask import Flask
from flask_restx import fields, Api, Resource

app = Flask(__name__)
api = Api(app)

model = api.model('Model', {
    'task': fields.String,
    'uri': fields.Url('todo_ep')
})

class TodoDao(object):
    def __init__(self, todo_id, task):
        self.todo_id = todo_id
        self.task = task

        # This field will not be sent in the response
        self.status = 'active'

@api.route('/todo')
class Todo(Resource):
    @api.marshal_with(model)
    def get(self, **kwargs):
        return TodoDao(todo_id='my_todo', task='Remember the milk')

The above example takes a python object and prepares it to be serialized. The marshal_with() decorator will apply the transformation described by model. The only field extracted from the object is task. The fields.Url field is a special field that takes an endpoint name and generates a URL for that endpoint in the response. Using the marshal_with() decorator also document the output in the swagger specifications. Many of the field types you need are already included. See the fields guide for a complete list.

Order Preservation

By default, fields order is not preserved as this have a performance drop effect. If you still require fields order preservation, you can pass a ordered=True parameter to some classes or function to force order preservation:

  • globally on Api: api = Api(ordered=True)
  • globally on Namespace: ns = Namespace(ordered=True)
  • locally on marshal(): return marshal(data, fields, ordered=True)

Full example

See the Full example section for fully functional example.