How to Add a Current Thread Safe Local Object to Flask Apps
Written by Sean on January 22, 2025
To do this you need to use werkzeug's LocalProxy object, which will proxy data to Flask's g built in global object.
Then it's just a matter of setting your data in the @before_request and @context_process decorators.
Then it's just a matter of setting your data in the @before_request and @context_process decorators.
from flask import Flask, session, g
from werkzeug.local import LocalProxy
from types import SimpleNamespace
from models import Session, User
# Set current with defaults.
# Note, I'm using SimpleNamespace instead of a dict for dot notation. E.g, "current.user"
current = LocalProxy(lambda: setattr(g, '_current', getattr(g, '_current', SimpleNamespace(user = User(name='Anonymous')))) or g._current)
app = Flask(__name__)
# Set user
@app.before_request
def before_request():
if 'user_id' in session:
current.user = Session.query(User).get(session['user_id'])
# Make current available to templates
@app.context_processor
def context_processor():
return {'current': current}
# More routes here...
@app.route("/")
def root_path():
return f'Hello {current.user.name}'
This is a nice way to namespace your custom data without too much trouble.