login_user, logout_user, and Sessions
Sign users in and out of a session.
login_user, logout_user, and Sessions is a free Flask Academy lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Flask Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Logging Someone In
Once a password checks out, you tell Flask-Login the user is signed in by calling login_user. That single call sets up the session for you.
from flask_login import login_user
login_user(user)A Typical Login Route
In a login view you find the user, verify the password, then call login_user. After that, redirect them to a real page like the dashboard.
if user and user.check_password(pw):
login_user(user)
return redirect(url_for("dashboard"))What login_user Stores
login_user does not save the whole object. It writes the user id into the session cookie, and your user_loader rebuilds the user later.
Remember Me
Pass remember=True to keep the user logged in after the browser closes. Flask-Login sets a long-lived cookie instead of a session-only one.
login_user(user, remember=True)Accessing current_user
Anywhere in a view you can read current_user to get the logged-in person. It is a proxy that always points at the active request's user.
from flask_login import current_user
name = current_user.usernameAnonymous Users
If nobody is logged in, current_user is an anonymous user object. Its is_authenticated is False, so you can branch on that safely.
if current_user.is_authenticated:
show_dashboard()Logging Out
To sign a user out, call logout_user. It clears their id from the session so the next request treats them as anonymous again.
from flask_login import logout_user
logout_user()A Logout Route
A logout view is tiny: call logout_user, then redirect home. There is no password to check, only the session to clear.
@app.route("/logout")
def logout():
logout_user()
return redirect(url_for("index"))Secret Key Required
Sessions ride in a signed cookie, so your app needs a SECRET_KEY. Without it, login_user raises an error and nothing works.
app.config["SECRET_KEY"] = "a-long-random-value"Sessions Are Per-User
Each browser gets its own signed cookie, so two users never see each other's session. Flask-Login keeps them cleanly separated.
Greeting the User
In templates you can use current_user too, since Flask-Login injects it. That makes a personalized navbar a one-line job.
<p>Hello, {{ current_user.username }}</p>Quick Check
A user clicks Log out. Which call ends their session?
Recap
You now login_user after a password check, read current_user anywhere, and call logout_user to end a session. A SECRET_KEY ties it together. 🔑
Frequently asked questions
Is the “login_user, logout_user, and Sessions” lesson free?
Yes — the full text of “login_user, logout_user, and Sessions” is free to read here on the web, and the Flask Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Flask Academy course, upgrade to CoddyKit PRO.
What will I learn in “login_user, logout_user, and Sessions”?
Sign users in and out of a session. You practise Flask Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Flask Academy?
No prior experience is required. Flask Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “login_user, logout_user, and Sessions” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Flask Academy lesson?
Yes. Every Flask Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Hash Passwords, Never Store Plaintext
- User Loader and the UserMixin
- login_user, logout_user, and Sessions
- Protect Views with login_required