Connexion is an open source API first REST framework for Python, built on top of Flask and based on Swagger, targeted for microservice development. Connexion automagically handles request routing, oauth2 security, request validation and response serialization based on a Swagger 2.0 Specification file in YAML, so you don’t have to care about boilerplate anymore. Because it is based on Flask it supports everything that Flask does, including deployment options and extensions.
At Zalando we’ve adopted “API First” as one of our key engineering principles, to ensure our API are robust, consistent, general and abstracted from specific implementation and use cases. But when we tried to implement this principle for the first time we were faced with the lack of a python framework to achieve it in a easy fashion - there were several frameworks that produce a swagger definition from the implementation but none that do it the other way around - so we decided to fill that gap.