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ImportError: cannot import name 'db' from partially initialized module 'flask_app'

Hello...

The following error is driving me crazy... I'm trying to do, what should be a simple tutorial and I keep receiving the following error:

2024-10-06 06:32:54,271: Error running WSGI application
2024-10-06 06:32:54,271: ImportError: cannot import name 'db' from partially initialized 
module 'flask_app' (most likely due to a circular import) 
(/home/kpuln/mysite/flask_app.py)
 2024-10-06 06:32:54,272:   File "/var/www/kpuln_pythonanywhere_com_wsgi.py", line 16, in <module>
2024-10-06 06:32:54,272:     from flask_app import app as application  # noqa
2024-10-06 06:32:54,272: 
2024-10-06 06:32:54,272:   File "/home/kpuln/mysite/flask_app.py", line 18, in <module>
2024-10-06 06:32:54,272:     from model import User
2024-10-06 06:32:54,272: 
2024-10-06 06:32:54,272:   File "/home/kpuln/mysite/model.py", line 2, in <module>
2024-10-06 06:32:54,272:     from flask_app import db
2024-10-06 06:32:54,273: ***************************************************
2024-10-06 06:32:54,273: If you're seeing an import error and don't know why,
2024-10-06 06:32:54,273: we have a dedicated help page to help you debug: 
2024-10-06 06:32:54,273: https://help.pythonanywhere.com/pages/DebuggingImportError/
2024-10-06 06:32:54,273: ***************************************************

The following is the code snippet from my model.py file:

from . import db
from flask_login import UserMixin
class User(UserMixin, db.Model):
      id         = db.Column(db.Integer, primary_key=True)  # primary_key
     email       = db.Column(db.String(255), unique=True)

The following is a snippet from the init.py file.

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_login import LoginManager

db = SQLAlchemy()

The error seems to be complaining about "db" being imported from the init.py file. I've tried 

from myapp import db

and that has not worked either.

Any suggestions ..?

kpuln | 11 posts | Oct. 6, 2024, 6:48 a.m. | permalink

You may have a circular import (that is where one module imports from another module that also imports from the first module - though there could be multiple steps in between).

In your case, it's because flask_app imports from model and then model in turn imports from flask_app again. You best bet is probably to place db in its own module so that flask_app and model can import that without there being a circular import.

Staff glenn | 10041 posts | PythonAnywhere staff | Oct. 6, 2024, 1:58 p.m. | permalink

Wow.... That worked... Thank you.. I really appreciate it....

Here is what I did...

I created a file db_file.py with the following as its contents

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

Then in my model.py file, I added 

from db_file import db

Again... Thanks for that suggestion..

kpuln | 11 posts | Oct. 7, 2024, 12:51 a.m. | permalink

Glad to hear that you made it work.

Staff fjl | 4966 posts | PythonAnywhere staff | Oct. 7, 2024, 7:50 a.m. | permalink