Connexion Cookbook

This section aims to be a cookbook of possible solutions for specific use cases of Connexion.

Custom type format

It is possible to define custom type formats that are going to be used by the Connexion payload validation on request parameters and response payloads of your API.

Let’s say your API deals with Products and you want to define a field price_label that have a “money” format value. You can create a format checker function and register that to be used to validate values of “money” format.

Example of a possible schema of Product having an attribute with “money” format that would be defined in your OpenAPI specification:

type: object
    type: string
    type: string
    format: money

Then we create a format checker function for that type of value:

import re

MONEY_RE = re.compile('^\$\s*\d+(\.\d\d)?')

def is_money(val):
    if not isinstance(val, str):
        return True
    return MONEY_RE.match(val)

The format checker function is expected to return True when the value matches the expected format and return False when it doesn’t. Also is important to verify if the type of the value you are trying to validate is compatible with the format. In our example we check if the val is of type “string” before performing any further checking.

The final step to make it work is registering our is_money function to the format “money” in json_schema library. For that, we can use the draft4 format checker decorator.

from jsonschema import draft4_format_checker

def is_money(val):

This is all you need to have validation for that format in your Connexion application. Keep in mind that the format checkers should be defined and registered before you run your application server. A full example can be found at

CORS Support

CORS (Cross-origin resource sharing) is not built into Connexion, but you can use the flask-cors library to set CORS headers:

import connexion
from flask.ext.cors import CORS

app = connexion.FlaskApp(__name__)

# add CORS support