ImportError: cannot import name 'JSONEncoder' from 'flask.json'

Question

I'm following a course on full-stack with Flask. My init.py looks like:

from flask import Flask
from config import Config
from flask_mongoengine import MongoEngine

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

db = MongoEngine()
db.init_app(app)

from application import routes

However, when importing from flask_mongoengine import MongoEngine, I'm getting an ImportError:

ImportError: cannot import name 'JSONEncoder' from 'flask.json' 

My venv looks like:

blinker==1.6.2
click==8.1.3
colorama==0.4.6
dnspython==2.3.0
email-validator==2.0.0.post2
Flask==2.3.2
flask-mongoengine==1.0.0
Flask-WTF==1.1.1
idna==3.4
itsdangerous==2.1.2
Jinja2==3.1.2
MarkupSafe==2.1.3
mongoengine==0.27.0
pymongo==4.4.0
python-dotenv==1.0.0
Werkzeug==2.3.6
WTForms==3.0.1

Is there anything I can do here to avoid this conflict? Thanks!

Mallard

Does this answer your question ? #76107950 – Ruzich

thanks for the info, not quite. I saw the post but it didn't make clear to me that I have to downgrade Flask – Feudalism

Answer 1

flask_mongoengine seems to be not currently maintained and does not work with current Flask versions. If you absolutely must use it, you need to downgrade your Flask version, which may (and likely will) get you into other trouble.

There is an issue on github regarding your error message: https://github.com/MongoEngine/flask-mongoengine/issues/522

The deprecation warning came with Flask 2.2.0 in 08/2022: Flask Changes

After a brief look at the repo, it seems the maintainer was already on it: https://github.com/MongoEngine/flask-mongoengine/blob/master/flask_mongoengine/json.py

Tidal

ooh, that's why. I saw a post on the mongodb help page (docs.mongoengine.org/projects/flask-mongoengine/en/latest/…) saying they don't have enough developers. Thanks a lot for the info. – Feudalism

Answer 2

It appears the repo is not maintained recently. Instead of degrading flask, you should install flask-mongoengine from this fork https://github.com/idoshr/flask-mongoengine/tree/1.0.1

uninstall current version by

 pip uninstall flask-mongoengine

And install using

pip install git+https://github.com/idoshr/[email protected]

This worked for me. I got this from here https://github.com/MongoEngine/flask-mongoengine/issues/525#issuecomment-1717066429

Auld

Answer 3

I downgrade my flask version and issue solved.

pip install flask==2.2.5

Slop