Getting 'RuntimeError: Working outside of application context.' when trying to import function from another Blueprint

Question

Initial Notes: The project uses Blueprints and below are the file structure and extracts of the code used...

File Structure:

/app
├── flaskapp/
│   ├── posts/
│   │   ├── __init__.py
│   │   ├── forms.py
│   │   ├── routes.py
│   │   ├── utils.py
│   ├── users/
│   │   ├── __init__.py
│   │   ├── forms.py
│   │   ├── routes.py
│   │   ├── utils.py
│   ├── main/
│   │   ├── __init__.py
│   │   ├── crons.py
│   │   ├── routes.py
│   ├── templates/
│   │   ├── users.html
│   ├── __init__.py
│   ├── config.py
│   ├── models.py
├── run.py

---

posts/utils.py

# Function to get all posts from DB

def get_all_posts():
    post = Post.query.order_by(Post.id.asc())
    return post

users/routes.py

# Importing 'get_all_posts' function from 'posts/utils.py'

from flaskapp.posts.utils import get_all_posts



users = Blueprint('users', __name__)


#All Users Route + Related Posts

@posts.route("/posts", methods=['GET'])
@login_required
def all_users():
    users = User.query.order_by(User.id.asc())
    return render_template('users.html', USERS=users, POSTS=get_all_posts())

main/crons.py

# Importing 'get_all_posts' function from 'posts/utils.py'

from flaskapp.posts.utils import get_all_posts


# A function to be called using 'scheduler' from 'flaskapp/__init__.py' on launch

def list_expired_posts():
    posts = get_all_posts()
    for p in posts:
        if p.expired == 1:
            print(p.title)

scheduler = BackgroundScheduler()
scheduler.add_job(func=list_expired_posts, trigger="interval", seconds=60)
scheduler.start()


# Terminate Scheduler on APP termination

atexit.register(lambda: scheduler.shutdown())

flaskapp/init.py

# __init__.py Main

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_login import LoginManager
from flaskapp.config import Config

db = SQLAlchemy()
login_manager = LoginManager()
login_manager.login_view = 'users.login'
login_manager.login_message_category = 'warning'


# Create APP Function
def create_app(config_class=Config):
    app = Flask(__name__)
    # Import Configuration from Config File Class
    app.config.from_object(Config)

    db.init_app(app)
    login_manager.init_app(app)

    # Import Blueprint objects
    from flaskapp.posts.routes import posts
    from flaskapp.users.routes import users
    from flaskapp.main.routes import main
    
    # Register Blueprints
    app.register_blueprint(posts)
    app.register_blueprint(users)
    app.register_blueprint(main)
    # END

    return(app)

# Calling scheduler function 'list_expired_posts' FROM '/main/crons.py' as a scheduled job to be triggered on app initiation

from flaskapp.main.crons import list_expired_posts
list_expired_posts()

Explanation:

I have the function 'get_all_posts()' located in 'posts/utils.py' which works fine when I import it and use it in another blueprint's routes.py file (ex.** users/routes.py**) as shown above.

But I'm getting the below error when importing the same function in another blueprint (specifically.** main/crons.py**) as shown above.

I'm trying to use the 'get_all_posts()' function from 'posts/utils.py' within the 'list_expired_posts()' in 'main/crons.py' and then calling the 'list_expired_posts()' function from 'flaskapp/init.py' to trigger it on launch and keep on executing it every 60 minutes.

Error:

RuntimeError: Working outside of application context.

This typically means that you attempted to use functionality that needed the current application. To solve this, set up an application context with app.app_context(). See the documentation for more information.

*Conclusion Notes + Steps attempted: *

I have already eliminated the 'Scheduler' temporarily and tried working only with the function itself and not even calling it from 'flaskapp/init.py'.

---

I have also tried moving the below code to the 'def create_app(config_class=Config)' section without any luck

from flaskapp.main.crons import list_expired_posts
list_expired_posts()

---

I have also tried creating a specific Blueprint for 'crons.py' and registering it to my 'flaskapp/init.py' but still got the same result.

---

As a final outcome, I am trying to call the 'get_all_posts()' FROM 'posts/utils.py', then filter out the 'expired posts' using the 'list_expired_posts()' function FROM 'main/crons.py' and schedule it to print the title of the expired posts every 60 minutes.

Since I've eliminated the scheduler already to test out, I'm quite sure this is not a scheduler issue but some import mixup I'm not figuring out.

---

I am also aware that the 'list_expired_posts()' can become as another function in 'posts/utils.py' and then directly call the function from there using the scheduler which I've also tried but keep getting the same error.

---

I also tried manually configuring the app's context as instructed in other posts but I keep getting the same error.

with app.app_context():

---

I'm not really a Python pro and I always try seeking multiple online resources prior to posting a question here but it seems like i'm out of luck this time. Your help is truly appreciated.

Answer 1

There is no blueprint in crons.py, which is expected as it's about scheduling, not routing.

Not being in a route, you get the error that the application context is missing, because effectively everything not in a route does not have an application context.

You might want to look into Flask-APScheduler, which you'd initialise in a similar way to Flask-SQLAlchemy and then use in your crons.py, it should carry the application context transparently.

PS. In users/routes.py you define a users Blueprint, but them seem to use a posts blueprint in the route decorator.

Ok, sorry for delay but here is a demo of using Flask-SQLAlchemy and Flask-APSscheduler to access the app context from scheduled tasks.

from flask import Blueprint, Flask
from flask_apscheduler import APScheduler
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()
scheduler = APScheduler()

users = Blueprint("users", __name__)


class User(db.Model):
    id = db.Column(db.Integer(), primary_key=True)
    username = db.Column(db.String(100), unique=True, nullable=False)

    def __repr__(self):
        return "<Name %r>" % self.id


def get_all_users():
    return User.query.all()


@users.route("/all", methods=["GET"])
def handle_users_all():
    return get_all_users()


@scheduler.task("cron", id="job_get_all_users", second="*/10")
def scheduled_get_all_users():
    with scheduler.app.app_context():
        get_all_users()


def create_app():

    app = Flask(__name__)

    app.register_blueprint(users)

    app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite:////tmp/74975778.db"
    db.init_app(app)
    with app.app_context():
        db.create_all()

    app.config["SCHEDULER_API_ENABLED"] = True
    scheduler.init_app(app)
    scheduler.start()

    return app

NB. this does not do anything useful in the scheduled task, I leave it up to you, but it can execute the utility function get_all_users on schedule.

Answer 2

I also don't think this is directly related to the scheduler. I think it works in your users/routes.py because it is inside a route. So it will only get called when you visit that route. And by then your app is fully created and has its context and whatever.

But in main/crons.py it is not inside a route so I think it will try to run it when it passes this import line in your flaskapp/init.py

from flaskapp.main.crons import list_expired_posts

Maybe you could try this: putting the scheduler part into a function

main/crons.py

# Importing 'get_all_posts' function from 'posts/utils.py'

from flaskapp.posts.utils import get_all_posts


# A function to be called using 'scheduler' from 'flaskapp/__init__.py' on launch

def list_expired_posts():
    posts = get_all_posts()
    for p in posts:
        if p.expired == 1:
            print(p.title)


def initiate_scheduler():
    scheduler = BackgroundScheduler()
    scheduler.add_job(func=list_expired_posts, trigger="interval", seconds=60)
    scheduler.start()

and then call that function in your run.py after you create the app

run.py

# first create the app
app = create_app()
# then start the scheduler
initiate_scheduler()

if __name__ == '__main__':
    app.run()
    # if you visit '/posts' in a browser it will call the get_all_posts() 
    # at this point in time after all the other code has ran.