Fix ImportError: cannot import name 'auth_bp' from 'app.auth' in Flask

This error occurs when Flask cannot import a Blueprint because of a circular import or the Blueprint object name does not match what you are importing. Fix it by deferring the import, using an application factory pattern, or ensuring the Blueprint variable name in the module matches the import statement exactly.

Reading the Stack Trace

Here's what each line means:

• File "/app/app/__init__.py", line 5, in <module>: The app package's __init__.py imports the auth Blueprint at module level, triggering the circular dependency chain.
• File "/app/app/auth/__init__.py", line 3, in <module>: The auth module imports from app.models, which in turn imports db from the app package that hasn't finished initializing.
• ImportError: cannot import name 'auth_bp' from partially initialized module 'app.auth': Python detects the circular import: app.auth is only partially loaded because it re-entered app/__init__.py before completing.

Common Causes

# app/__init__.py
from flask import Flask
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()
from app.auth import auth_bp  # circular import

def create_app():
    app = Flask(__name__)
    db.init_app(app)
    app.register_blueprint(auth_bp)
    return app

# app/auth/__init__.py
from flask import Blueprint
bp = Blueprint('auth', __name__)  # named 'bp' not 'auth_bp'

# app/__init__.py
from app.auth import auth_bp  # wrong name

# Directory structure missing __init__.py:
# app/auth/routes.py  (exists)
# app/auth/__init__.py  (missing!)

from app.auth import auth_bp  # fails

The Fix

Move the Blueprint import inside the create_app factory function so it runs after db and other extensions are fully initialized. This breaks the circular import chain because app/__init__.py finishes defining db before auth tries to import it.

# app/__init__.py
from flask import Flask
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()
from app.auth import auth_bp  # top-level import causes circular dependency

def create_app():
    app = Flask(__name__)
    db.init_app(app)
    app.register_blueprint(auth_bp)
    return app

# app/__init__.py
from flask import Flask
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

def create_app():
    app = Flask(__name__)
    db.init_app(app)

    from app.auth import auth_bp  # deferred import inside factory
    app.register_blueprint(auth_bp)
    return app

Testing the Fix

import pytest
from app import create_app

@pytest.fixture
def app():
    app = create_app()
    app.config['TESTING'] = True
    return app

def test_app_creates_without_import_error(app):
    assert app is not None

def test_auth_blueprint_registered(app):
    assert 'auth' in [bp.name for bp in app.iter_blueprints()]

def test_auth_routes_accessible(app):
    client = app.test_client()
    response = client.get('/auth/login')
    assert response.status_code in (200, 302)

Run your tests:

pytest tests/ -v

Pushing Through CI/CD

git checkout -b fix/flask-blueprint-circular-import,git add app/__init__.py,git commit -m "fix: defer blueprint import to break circular dependency",git push origin fix/flask-blueprint-circular-import

Your CI config should look something like this:

name: CI
on:
  pull_request:
    branches: [main]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-python@v5
        with:
          python-version: '3.12'
          cache: 'pip'
      - run: pip install -r requirements.txt
      - run: pytest tests/ -v --tb=short
      - run: flake8 app/

The Full Manual Process: 18 Steps

Here's every step you just went through to fix this one bug:

1. Notice the error alert or see it in your monitoring tool
2. Open the error dashboard and read the stack trace
3. Identify the file and line number from the stack trace
4. Open your IDE and navigate to the file
5. Read the surrounding code to understand context
6. Reproduce the error locally
7. Identify the root cause
8. Write the fix
9. Run the test suite locally
10. Fix any failing tests
11. Write new tests covering the edge case
12. Run the full test suite again
13. Create a new git branch
14. Commit and push your changes
15. Open a pull request
16. Wait for code review
17. Merge and deploy to production
18. Monitor production to confirm the error is resolved

Total time: 30-60 minutes. For one bug.

pip install bugstack

import bugstack

bugstack.init(api_key=os.environ["BUGSTACK_API_KEY"])

Deploying the Fix (Manual Path)

1. Run pytest locally to confirm the blueprint imports correctly.
2. Open a pull request with the deferred import change.
3. Wait for CI checks to pass on the PR.
4. Have a teammate review and approve the PR.
5. Merge to main and verify the app starts cleanly in staging.

Frequently Asked Questions