Like Arun says, I was interested in solving this (or at least a critical subset of this) at the level of dataclasses/attrs since I figure those can be used downstream.

Since the discussion sprung back to life somehow, a progress update: I've started a PR to the attrs plugin with the necessary updates: David Euresti has volunteered to provide feedback while I polish it up and fix the tests. I'm very new to the Mypy codebase so it might be a while though.

On Tue, May 18, 2021 at 4:28 PM Guido van Rossum <> wrote:
If you want that to happen you should probably lobby specific web frameworks (e.g. by starting a discussion in their issue tracker).

On Tue, May 18, 2021 at 06:32 Arun Sharma <> wrote:

Thank you for bringing this up! I hope popular web frameworks start adopting dataclasses for representing their models and use type safe method chaining APIs to interface with business logic.

On Fri, Apr 23, 2021 at 10:18 AM Tin Tvrtković <> wrote:

from dataclasses import fields

user_projection: tuple[str] = await fetch_projection(User, id=1, fields(User)[1])

In fquery [1], this would be spelled as:


My request is to consider that some of the implementations may not be presenting a flat result set. For example this query:

       resp = (
            .project(["name", ":id"])

Without the "to_json()" it produces a graph of similarly nested python objects.

Type checkers that can understand these queries and provide type safety to consumers of the result set would be a great reason for web frameworks to adopt this vs the status quo where the internals of a relational database are exposed via a python API.

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