python module_error ai_generated true

ImportError: cannot import name 'db' from partially initialized module 'app' (most likely due to a circular import)

ID: python/flask-circular-import

Also available as: JSON · Markdown · 中文
80%Fix Rate
88%Confidence
0Evidence
2024-02-08First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.x active — — —

Root Cause

Two modules import each other at module load time, typically models importing app and app importing models.

generic

中文

两个模块在加载时互相导入，通常是 models 导入 app 而 app 又导入 models。

Workarounds

  1. 93% success 
    def create_app():
    app = Flask(__name__)
    db.init_app(app)
    return app
  2. 91% success 
    # extensions.py
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()

Dead Ends

Common approaches that don't work:

  1. 85% fail

    Only changes which side fails first; cycle remains.

  2. 90% fail

    Leaves db undefined and crashes later.