6

I keep getting the error 'Flask' object has no attribute 'session_cookie_name' right at initialization on an app that used to work.

I built a smaller test app to test it and noticed that if I remove the line app.config["SESSION_TYPE"] = "filesystem" the error goes away. Problem is I need to use sessions in my Flask app and, since it is for testing, I would prefer to use the filesystem to store session data. here is my mini program for testing... I don't know what I am missing, this used to work fine and code examples online do it exactly this way but I keep getting the same error.

This is the error I receive

from flask import Flask, render_template,redirect, url_for, request, session
from flask_session import Session

app = Flask(__name__)

app.config["SESSION_PERMANENT"] = False
app.config["SESSION_TYPE"] = "filesystem"

Session(app)

@app.route("/")
def index():
    session["test"] = "test"
    return render_template ('index.html')

This worked before. It is all of the sudden not working. I have tried installing a different version of Flask_Session. I have tried adding the "SESSION_COOKIE_NAME" to app.config before Session(app) even though I understand its default is session. Nothing so far has worked or changed the error message.

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3 Answers 3

Reset to default
8

With the upgraded Flask, you also need an upgraded flask-session (which I note that you are using)

As you have discovered, Flask >= 2.3.0 removed those names. Flask-session >= 0.4 fixes that. Check your requirements.txt. In my requirements.txt it just had a minimum version for Flask (allowing it to be upgraded on a new build) but had flask-session fixed at an older version, so the mismatch broke things.

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3 Comments

In version 0.5.0 of Flask-Session, the changelog states that it has: Replace use of session_cookie_name for Flask 2.3 compatibility
session_cookie_name was removed in Flask 2.3.0 (not 2.3.1): github.com/pallets/flask/blob/2.3.0/CHANGES.rst
edited per comment
1

This error happens when the currently used version of Flask does not have the session_cookie_name attribute. This attribute was added in Flask 2.0, so if you are using an older version of Flask, you will need to upgrade to a newer version.

Just upgrade Flask by executing the command pip install --upgrade Flask

Note: If you are using a virtual environment, be sure to activate it before upgrading.

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Actually, I was running the latest Flask, version 2.3.1. But, I did look at the version release notes and as of 2.3.0 The session_cookie_name, send_file_max_age_default, use_x_sendfile, propagate_exceptions, and templates_auto_reload properties on app are removed.. So I have downgraded and it is now working. Thank you for pointing me in the right direction. Now I just need to figure out how to get the same functionality out of the latest Flask version. Thank you.
0

Fixed with:

pip install Flask-session==0.5.0

So working env versions:

pip freeze
blinker==1.7.0
cachelib==0.10.2
certifi==2024.2.2
charset-normalizer==3.3.2
click==8.1.7
colorama==0.4.6
Flask==3.0.1
Flask-OAuthlib==0.9.6
Flask-Session==0.3.2
idna==3.6
itsdangerous==2.1.2
Jinja2==3.1.3
MarkupSafe==2.1.5
oauthlib==2.1.0
python-dateutil==2.8.2
requests==2.31.0
requests-oauthlib==1.1.0
six==1.16.0
urllib3==2.2.0
Werkzeug==3.0.1
xero_python==1.5.3
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