flask-sqlalchemy: AttributeError: type object has no attribute 'query', works in ipython

Question

I'm creating a new flask app using flask-sqlalchemy and flask-restful with Python 3.4. I've defined my User model as such:

from mytvpy import db
from sqlalchemy.ext.declarative import declared_attr


class BaseModel(db.Model):
    __abstract__ = True

    id = db.Column(db.Integer, primary_key=True)
    created = db.Column(db.TIMESTAMP, server_default=db.func.now())
    last_updated = db.Column(db.TIMESTAMP, server_default=db.func.now(), onupdate=db.func.current_timestamp())

    @declared_attr
    def __tablename__(cls):
        return cls.__name__


class User(BaseModel):

    username = db.Column(db.String(255), unique=True)
    password = db.Column(db.String(255))
    email = db.Column(db.String(255), unique=True)

    def __init__(self, username, password, email):
        super(User, self).__init__()
        self.username = username
        self.password = password
        self.email = email

If I try to query in ipython, it works:

In [15]: from mytvpy.models.base import User

In [16]: User.query.all()
Out[16]: [<mytvpy.models.base.User at 0x7fac65b1c6a0>]

But if I try to hit it from an endpoint:

class User(Resource):

    def get(self, user):
        return User.query.filter(User.username==user).scalar()

It craps out:

Traceback (most recent call last):
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask/app.py", line 1836, in __call__
    return self.wsgi_app(environ, start_response)
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask/app.py", line 1820, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask_restful/__init__.py", line 270, in error_router
    return original_handler(e)
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask/app.py", line 1403, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask/_compat.py", line 32, in reraise
    raise value.with_traceback(tb)
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask/app.py", line 1817, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask/app.py", line 1477, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask_restful/__init__.py", line 270, in error_router
    return original_handler(e)
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask/app.py", line 1381, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask/_compat.py", line 32, in reraise
    raise value.with_traceback(tb)
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask/app.py", line 1475, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask/app.py", line 1461, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask_restful/__init__.py", line 471, in wrapper
    resp = resource(*args, **kwargs)
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask/views.py", line 84, in view
    return self.dispatch_request(*args, **kwargs)
  File "/home/rich/anaconda/envs/mytv/lib/python3.5/site-packages/flask_restful/__init__.py", line 581, in dispatch_request
    resp = meth(*args, **kwargs)
  File "/home/rich/prj/mytv/mytvpy/blueprints/base.py", line 12, in get
    return User.query.filter(User.username==user).scalar()
AttributeError: type object 'User' has no attribute 'query'

Solution

You have two classes named User, one extending BaseModel and one extending Resource. The latter is shadowing the former.

Change how you import/reference the model and your code should work:

from mytvpy.models import base

base.User.query.all()

Comments

[postelrich]

thanks, thats why some programming methodology say not to work more than 8 hr days!