从较低模块导入时的ImportError

Question

I'm trying to import an object named db (SQLAlchemy object) in in a module of my Flask Project in order to use the SQLAlchemy in my models ( models.py ). Assuming my package is named Foo and contains the db object in his __init__.py file , when i try to do a from Foo import db , i get the following error:

ImportError: cannot import name db

I'm using Flask Blueprint to dispatch my project into two applications (dashboard and frontend) and each of them contains an __init__.py file. Only the models.py is throwing this error, i got some imports in my views file (as importing the login manager) and everything goes well.

Any idea of what it could be ?

UPDATE : The traceback

Traceback (most recent call last):
    File "run.py", line 4, in <module>
        from kuchiyose import app
    File "/path_to_project/kuchiyose/kuchiyose/__init__.py", line 60, in <module>
        from kuchiyose import dashboard, frontend
    File "/path_to_project/kuchiyose/kuchiyose/dashboard/__init__.py", line 10, in <module>
        from dashboard import views
    File "/path_to_project/kuchiyose/kuchiyose/dashboard/__init__.py", line 10, in <module>
        from dashboard import views
    File "/path_to_project/kuchiyose/kuchiyose/dashboard/views.py", line 8, in <module>
        from kuchiyose.dashboard.models import User
    File "/path_to_project/kuchiyose/kuchiyose/dashboard/models.py", line 3, in <module>
        from kuchiyose import db

ImportError: cannot import name db

Answer 1

First, thanks for the help. Concerning my second question : "How to import Flask models into views without having a circular import issue (when using SQLAlchemy)", i found a solution. It consists to setup the SQLAlchemy object not into the application __init__.py file but into the models.py file itself. With that, you can import it in your views.py file without problem.

My models.py file, now:

from kuchiyose import app
from flask.ext.sqlalchemy import SQLAlchemy

db = SQLAlchemy(app)

And my views.py

from kuchiyose.dashboard import models

Answer 2

This is an old one but showed up as a top result in my search.

I have a project that has model declarations in a few different places rather than a consolidated models.py file so this solution wouldn't be ideal. I found importing your views AFTER establishing the db object works as well.

from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config.from_object('config')

db = SQLAlchemy(app)

# Now Register routes
# db is now defined so app import db will now work)
from routes.user import user as user_routes
app.register_blueprint(user_routes)

Answer 3

there appears to be circular imports:

• kuchiyose/__init__.py imports from kuchiyose.dashboard.views
• kuchiyose/dashboard/views.py imports from kuchiyose.dashboard.models
• kuchiyose/dashboard/models.py imports from kuchiyose

see eg Circular (or cyclic) imports in Python for more info...