Please check example directory.

Important: you need to enable the plugin in your mypy config file, and pycharm doesn't support mypy plugin.

[mypy]
plugins = flasksqlamypy

from typing import TYPE_CHECKING
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

if TYPE_CHECKING:
    from flask_sqlalchemy.model import Model

    BaseModel = db.make_declarative_base(Model)
else:
    BaseModel = db.Model

class User(BaseModel):
    __tablename__ = 'users'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String)

user = User(id=42, name=42)  # Error: Incompatible type for "name" of "User"
                             # (got "int", expected "Optional[str]")
user.id  # Inferred type is "int"
User.name  # Inferred type is "Column[Optional[str]]"

pip install git+https://github.com/ssfdust/flask-sqlalchemy-stubs.git

You can define a classmethod with self typed, which makes jedi completion to work. Please check examples/sample.py for the entire example.