Skip to content

First try on Quart an asyncio re-implementation of Flask#

Flask is a little bit old-fashioned today (I know it's still widely used), as it's not async native, among others. When I prepared my fastapi-demo this weekend, I discovered a new framework called Quart, which is maintained by Pallet Project, the same community maintaining Flask. They said "Quart is an asyncio re-implementation of the popular Flask micro framework API. This means that if you understand Flask you understand Quart.". So I decided to give it a try.


To test, I just searched flask sqlalchemy sample on Google, and got this sample repo: app-generator/sample-flask-sqlalchemy. It's a Web UI based on Flask. I cloned it, and tried to convert it to Quart.

Firstly, install the project, and run the Flask app, everything is fine.

Now, let's convert it to Quart. There's already a Flask to Quart migration guide on the official site. Basically, it's just replacing flask with quart in the import statements, and adding async/await to the view and testing functions.

In addition to what the guide says, I also need to:

  1. add await to the render_template().
  2. use new sqlalchemy db models syntax, with from sqlalchemy.orm import Mapped, mapped_column, this is not related to Quart, but I installed the newest version of sqlalchemy, and the old syntax is deprecated.
  3. install the extension quart-flask-quart, and import it in the file where app is created, and replace app with QuartFlaskQuart(__name__). This extension patches the Quart app to be compatible with many popular Flask extensions, so that flask-sqlalchemy, flask-login, flask-caching, flask-limiter, etc. can be used in Quart.

After these small changes, the Quart app runs successfully, and the Web UI is still working. Although my test is very light, this is really a very good starting point for me. Wonderful!

Furthermore, I also tried Quart-Schema, a Quart extension that provides schema validation and auto-generated API documentation, similar to FastAPI. After testing, it works well, leveraging msgspec and Pydantic behind the scenes, which is really impressive!

My conclusion is, if you are using Flask, and want to try the async, Quart might be a good choice. It's easy to migrate from Flask, and many of the Flask extensions are still usable.