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"""
Flask Login System with SQLite
Features:
- Signup (create new account)
- Login (check user credentials)
- Session (to remember login state)
- Cookies (to store last visit info)
- "Remember Me" option (stay logged in even after closing browser)
"""
from flask import Flask, render_template, request, redirect, url_for, session, make_response
import sqlite3
from datetime import timedelta
# Flask App Setup
app = Flask(__name__)
# Secret key is used to sign session data (must be kept secret in real apps!)
app.secret_key = "supersecretkey"
# Permanent sessions last for 7 days (used when "Remember Me" is checked)
app.permanent_session_lifetime = timedelta(days=7)
# Helper function to connect to SQLite database
def get_db_connection():
# Connect to SQLite database (creates file users.db if it doesn’t exist)
conn = sqlite3.connect("users.db")
conn.row_factory = sqlite3.Row # Makes rows behave like dictionaries
return conn
# Initialize database with a "users" table
def init_db():
conn = get_db_connection()
conn.execute("""
CREATE TABLE IF NOT EXISTS users (
id INTEGER PRIMARY KEY AUTOINCREMENT, -- Auto-increment ID
username TEXT UNIQUE NOT NULL, -- Unique username
password TEXT NOT NULL -- Password (plain text for demo, should use hashing!)
)
""")
conn.commit()
conn.close()
# Call database initialization at startup
init_db()
# Home Page (only logged-in users can see this)
@app.route("/")
def home():
# Check if the user is logged in using session
if "username" in session:
username = session["username"] # Get logged-in username from session
# Get last visit message from cookie (if not found, show default message)
last_visit = request.cookies.get("last_visit", "First time visiting!")
return render_template("home.html", username=username, last_visit=last_visit)
# If not logged in, redirect to login page
return redirect(url_for("login"))
# Signup Page
@app.route("/signup", methods=["GET", "POST"])
def signup():
if request.method == "POST": # When user submits the form
username = request.form["username"]
password = request.form["password"]
conn = get_db_connection()
try:
# Insert new user into database
conn.execute("INSERT INTO users (username, password) VALUES (?, ?)", (username, password))
conn.commit()
conn.close()
# After signup, redirect to login page
return redirect(url_for("login"))
except sqlite3.IntegrityError:
# This happens if the username already exists
return "Username already exists! Try another."
# If GET request, show signup form
return render_template("signup.html")
# Login Page
@app.route("/login", methods=["GET", "POST"])
def login():
if request.method == "POST": # When user submits login form
username = request.form["username"]
password = request.form["password"]
# Checkbox value: will be "on" if user ticks "Remember Me"
remember = request.form.get("remember")
# Check if username & password exist in database
conn = get_db_connection()
user = conn.execute("SELECT * FROM users WHERE username=? AND password=?",
(username, password)).fetchone()
conn.close()
if user:
# ✅ User found → start session
if remember == "on":
# Session will survive browser close (7 days)
session.permanent = True
else:
# Session ends when browser closes
session.permanent = False
# Store username inside session
session["username"] = username
# Create response with cookie
resp = make_response(redirect(url_for("home")))
# Save a cookie with "last visit" info
# If "Remember Me" checked → cookie valid for 7 days
# Else → cookie lasts only until browser closes
resp.set_cookie("last_visit", "Welcome back, " + username,
max_age=(7*24*60*60 if remember == "on" else None))
return resp
else:
# If username or password is wrong
return "Invalid username or password. Try again."
# If GET request, show login form
return render_template("login.html")
# Logout Page
@app.route("/logout")
def logout():
# Remove username from session
session.pop("username", None)
# Also delete the "last_visit" cookie
resp = make_response(redirect(url_for("login")))
resp.set_cookie("last_visit", "", expires=0)
return resp
# Run the App
if __name__ == "__main__":
app.run(debug=True, host="0.0.0.0", port=5000) |