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I found this code that times each response, but I'm not sure where g is supposed to come from. What is g?
@app.before_request def before_request(): g.start = time.time() @app.teardown_request def teardown_request(exception=None): diff = time.time() - g.start print diff 
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g is an object for storing data during the application context of a running Flask web app. g can also be imported directly from the flask module instead of flask. globals , so you will often see that shortcut in example code.
session gives you a place to store data per specific browser. As a user of your Flask app, using a specific browser, returns for more requests, the session data is carried over across those requests. g on the other hand is data shared between different parts of your code base within one request cycle.
__name__ is just a convenient way to get the import name of the place the app is defined. Flask uses the import name to know where to look up resources, templates, static files, instance folder, etc.
The application context is a good place to store common data during a request or CLI command. Flask provides the g object for this purpose. It is a simple namespace object that has the same lifetime as an application context.
g is an object provided by Flask. It is a global namespace for holding any data you want during a single app context. For example, a before_request handler could set g.user, which will be accessible to the route and other functions.
from flask import g @app.before_request def load_user(): user = User.query.get(request.session.get("user_id")) g.user = user @app.route("/admin") def admin(): if g.user is None or not g.user.is_admin: return redirect(url_for("index")) An app context lasts for one request / response cycle, g is not appropriate for storing data across requests. Use a database, redis, the session, or another external data source for persisting data.
Note that the dev server and any web server will output timing information in the logs already. If you really want to profile your code, you can use the Werkzeug application profiler.
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