AttributeError: module 'api.db' has no attribute 'Model' on Flask

Question

Hello I have the following folder structure

    .
    ├── api
    │   ├── users
    │   │   ├── __init__.py
    │   │   ├── model.py
    │   │   └── routes.py
│   ├── |__init__.py
    ├── __init__.py
    ├── requirements.txt
    └── server.py

In api.__init__.py I have the following code:

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from api import users
from flask_restful import Api

db = SQLAlchemy()


def create_app(env):
    app = Flask(__name__)
    db.init_app(app)
    api = Api(app)
    users.register_routes(api)
    return app

and in users/model.py I have the following code:

from sqlalchemy import Column, Integer, String
from .. import db

class User(db.Model):
    __tablename__ = 'users'
...

And in server.py I have the following code:

import os

from api import create_app

app = create_app(os.getenv("ENV"))
if __name__ == "__main__":
    app.run(port=os.getenv("PORT"), debug=os.getenv("DEBUG")=='True')

The problem is that when I execute server.py I have the following error:

AttributeError: module 'api.db' has no attribute 'Model'

How can I solve this error?

Thanks

Are you sure db is not overridden inside api/__init__.py ? try to confirm it with a quick print(db) right after from .. import db. Attaching the full exception will be helpful too. — Mohamed Feddad
– Mohamed Feddad, Commented Jul 5, 2020 at 10:44
The print return the following: <module 'api.db' (namespace)>, updated with all code of api.__init__ — Tlaloc-ES
– Tlaloc-ES, Commented Jul 5, 2020 at 10:50
That's not right, i think it should be <SQLAlchemy engine=None> so my guess it's overridden with something else. Probably you have a api/db.py ? — Mohamed Feddad
– Mohamed Feddad, Commented Jul 5, 2020 at 10:55

cizario · Accepted Answer · 2020-07-05 10:58:18Z

1

i would suggest you making some changes to the structure of your project to avoid circular import issue and prefer importing your app as package not as a module and also as a good practice __init __.py is kept just for import and some metadata like __author__ and __version__

api

  .. errors (blueprint)
    .. __init__.py
    .. routes.py


  .. users (blueprint)
    .. __init__.py
    .. model.py
    .. routes.py

  .. extensions.py

  .. __init__.py
  .. app.py (here where your define "create_app()" function)


server.py
requirements.txt

in api/users/__init __.py:

from .routes import bp

in api/users/models.py:

from api.extensions import db

# from sqlalchemy import Column, Integer, String  # You don't need this since you already imported the db oject 

class User(db.Model):
    __tablename__ = 'users'

    id = db.Column(db.Integer, primary_key=True)  # here 
...

in api/users/routes.py:

from flask import Blueprint, request, jsonify ..

from api.extensions import db  # maybe you need it here
from .models import User  # Your model


bp = Blueprint('users', __name__)  # instantiate your 'users' Blueprint


@bp.route('/', methods=['GET', 'POST']) 
def index():

    ..
    
    return jsonify(..)

in /api/extensions.py, define the Flask extensions needed for your app

from flask_sqlalchemy import SQLAlchemy
..

db = SQLAlchemy()
..

in /api/__init __.py:

from .app import create_app

in /api/app.py:

from flask import Flask
..

def create_app(config_object):
    """Create a Flask application using the app factory pattern."""

    app = Flask(__name__)

    """Load configuration."""
    # app.config.from_object(CONFIGS[config_object])  # an example 

..

    """Init app extensions."""
    from .extensions import db
    db.init_app(app)

..

    """Register blueprints."""
    from .errors import bp as errors_bp
    app.register_blueprint(errors_bp)

    from .users import bp as users_bp
    app.register_blueprint(users_bp, url_prefix='/users')

..
    
    return app

in /server.py:

import os

from api import create_app


app = create_app(os.getenv("ENV", "development"))

if __name__ == "__main__":
    app.run(port=os.getenv("PORT", 5000), debug=os.getenv("DEBUG", True)

answered Jul 5, 2020 at 10:58

cizario

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3 Comments

Tlaloc-ES Over a year ago

Great answer, can you tell me where I did circular imports?

cizario Over a year ago

i just mean, since flask is un-opinionated framework, with good project structure you can avoid many issues (circular imports - not your case - ), make your app maintainable and easy to debug and extensible.

cizario Over a year ago

if you want to register routes just prefer @bp.route() decorator in users/routes.py or at the bottom of users/routes.py you can call bp.add_url_rule('/', 'index', index)

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