Run Code Before the First Request in Flask

To run some code (once) before the first request in a Flask app, you could use the before_first_request decorator. However, since it's deprecation in Flask 2.3.0.

The recommended way is to use it after app config by manually pushing the app context, like so:

app.py

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()


def create_app():
  app = Flask(__name__)

  # Configure the app
  app.config.from_object('your_config_module')

  # Initialize extensions
  db.init_app(app)

  # Run some custom startup code
  with app.app_context():
    # This code runs once the application context is available
    print("Running startup tasks...")
    # Example: create tables if not already present
    db.create_all()

  # Register blueprints
  # from .routes import main
  # app.register_blueprint(main)

  return app

info

This example is using the app factory pattern. If you're using the app object directly, you can run the code after app creation.