300 lines
8.8 KiB
Markdown
300 lines
8.8 KiB
Markdown
# Flask Authentication Application
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A complete full-stack web application with user authentication built with Flask and SQLite.
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## 📁 Project Structure
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flask_app/
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├── app.py
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├── database.py
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├── users.py
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├── users.db
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├── requirements.txt
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├── venv/
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└── templates/
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├── base.html
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├── home.html
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├── login.html
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└── register.html
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text
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## 🚀 Quick Start
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### 1. Create Project Scaffold (One Command!)
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```bash
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# Create all empty files and folders with one command:
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mkdir -p flask_app/templates && cd flask_app && touch app.py database.py users.py users.db requirements.txt && mkdir -p venv && touch templates/base.html templates/home.html templates/login.html templates/register.html && cd .. && echo "✅ All empty files created in 'flask_app/':" && find flask_app/ -type f | sort
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for windows
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mkdir -Force flask_app\templates; cd flask_app; ni app.py, database.py, users.py, users.db, requirements.txt; mkdir -Force venv; ni templates\base.html, templates\home.html, templates\login.html, templates\register.html; cd ..; Write-Host "✅ All empty files created in 'flask_app/':" -ForegroundColor Green; Get-ChildItem -Path flask_app -File -Recurse | Sort-Object FullName | Select-Object -ExpandProperty FullName
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2. Setup Virtual Environment
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bash
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cd flask_app
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# Create virtual environment
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python -m venv venv
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# Activate virtual environment (Windows PowerShell)
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venv\Scripts\Activate.ps1
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# If you get an error:
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Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser
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venv\Scripts\Activate.ps1
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# Activate virtual environment (Mac/Linux)
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# source venv/bin/activate
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3. Install Dependencies
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bash
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pip install flask werkzeug flask-wtf
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pip freeze > requirements.txt
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4. Fill Files with Code
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Now fill the empty files with the code below:
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app.py - Main Flask application:
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python
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from flask import Flask, render_template, request, redirect, url_for, session, flash
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import database
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import users
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app = Flask(__name__)
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app.secret_key = 'your-secret-key-change-this-in-production'
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database.init_db()
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@app.route('/')
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def home():
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return render_template('home.html')
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@app.route('/register', methods=['GET', 'POST'])
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def register():
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if request.method == 'POST':
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username = request.form['username']
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email = request.form['email']
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password = request.form['password']
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success, message = users.register_user(username, email, password)
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if success:
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flash('Registration successful! Please login.', 'success')
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return redirect(url_for('login'))
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else:
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flash(message, 'error')
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return render_template('register.html')
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@app.route('/login', methods=['GET', 'POST'])
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def login():
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if request.method == 'POST':
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username = request.form['username']
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password = request.form['password']
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success, result = users.login_user(username, password)
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if success:
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session['user_id'] = result['id']
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session['username'] = result['username']
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flash('Login successful!', 'success')
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return redirect(url_for('home'))
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else:
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flash(result, 'error')
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return render_template('login.html')
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@app.route('/logout')
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def logout():
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session.clear()
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flash('You have been logged out.', 'success')
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return redirect(url_for('home'))
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if __name__ == '__main__':
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app.run(debug=True)
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database.py - Database operations:
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python
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import sqlite3
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def init_db():
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conn = sqlite3.connect('users.db')
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cursor = conn.cursor()
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cursor.execute('''
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CREATE TABLE IF NOT EXISTS users (
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id INTEGER PRIMARY KEY AUTOINCREMENT,
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username TEXT UNIQUE NOT NULL,
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email TEXT UNIQUE NOT NULL,
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password TEXT NOT NULL,
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created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
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)
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''')
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conn.commit()
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conn.close()
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def get_db_connection():
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conn = sqlite3.connect('users.db')
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conn.row_factory = sqlite3.Row
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return conn
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users.py - User authentication:
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python
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from werkzeug.security import generate_password_hash, check_password_hash
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import database
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def register_user(username, email, password):
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hashed_password = generate_password_hash(password, method='sha256')
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try:
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conn = database.get_db_connection()
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conn.execute('INSERT INTO users (username, email, password) VALUES (?, ?, ?)',
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(username, email, hashed_password))
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conn.commit()
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conn.close()
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return True, None
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except sqlite3.IntegrityError as e:
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return False, 'Username or email already exists!'
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def login_user(username, password):
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conn = database.get_db_connection()
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user = conn.execute('SELECT * FROM users WHERE username = ?', (username,)).fetchone()
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conn.close()
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if user and check_password_hash(user['password'], password):
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return True, user
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else:
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return False, 'Invalid username or password!'
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5. Fill HTML Templates
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templates/base.html:
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html
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>{% block title %}Flask Auth App{% endblock %}</title>
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<style>
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body { font-family: Arial, sans-serif; max-width: 500px; margin: 50px auto; padding: 20px; }
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.alert { padding: 10px; margin: 10px 0; border-radius: 5px; }
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.success { background: #d4edda; color: #155724; }
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.error { background: #f8d7da; color: #721c24; }
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form { display: flex; flex-direction: column; gap: 10px; }
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input, button { padding: 10px; margin: 5px 0; }
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.nav { margin-bottom: 20px; }
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.nav a { margin-right: 15px; text-decoration: none; color: #007bff; }
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</style>
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</head>
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<body>
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<div class="nav">
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<a href="{{ url_for('home') }}">Home</a>
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{% if session.get('user_id') %}
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<a href="{{ url_for('logout') }}">Logout</a>
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{% else %}
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<a href="{{ url_for('login') }}">Login</a>
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<a href="{{ url_for('register') }}">Register</a>
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{% endif %}
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</div>
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{% with messages = get_flashed_messages(with_categories=true) %}
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{% if messages %}
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{% for category, message in messages %}
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<div class="alert {{ category }}">{{ message }}</div>
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{% endfor %}
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{% endif %}
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{% endwith %}
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{% block content %}{% endblock %}
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</body>
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</html>
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templates/home.html:
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html
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{% extends "base.html" %}
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{% block title %}Home{% endblock %}
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{% block content %}
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<h1>Welcome to Flask Auth App</h1>
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{% if session.get('user_id') %}
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<h2>Hello, {{ session.get('username') }}!</h2>
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<p>You are logged in.</p>
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<p>This is your dashboard.</p>
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{% else %}
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<p>Please <a href="{{ url_for('login') }}">login</a> or <a href="{{ url_for('register') }}">register</a>.</p>
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{% endif %}
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{% endblock %}
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templates/register.html:
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html
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{% extends "base.html" %}
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{% block title %}Register{% endblock %}
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{% block content %}
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<h2>Register</h2>
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<form method="POST" action="{{ url_for('register') }}">
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<input type="text" name="username" placeholder="Username" required>
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<input type="email" name="email" placeholder="Email" required>
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<input type="password" name="password" placeholder="Password" required>
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<button type="submit">Register</button>
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</form>
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<p>Already have an account? <a href="{{ url_for('login') }}">Login here</a></p>
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{% endblock %}
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templates/login.html:
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html
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{% extends "base.html" %}
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{% block title %}Login{% endblock %}
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{% block content %}
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<h2>Login</h2>
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<form method="POST" action="{{ url_for('login') }}">
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<input type="text" name="username" placeholder="Username" required>
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<input type="password" name="password" placeholder="Password" required>
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<button type="submit">Login</button>
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</form>
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<p>Don't have an account? <a href="{{ url_for('register') }}">Register here</a></p>
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{% endblock %}
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6. Run the Application
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bash
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python app.py
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Visit: http://127.0.0.1:5000
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📋 File Purpose
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File Purpose Contains
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app.py Main Flask application Routes, request handling, session management
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database.py Database operations Connection functions, table creation, SQL queries
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users.py User authentication Register, login, password hashing functions
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templates/ HTML templates Base template and page-specific templates
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requirements.txt Dependencies List of Python packages needed
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users.db Database file SQLite database with user data
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🔒 Security Notes
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This is a learning example, not production-ready
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Passwords are hashed using Werkzeug
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Never store plain text passwords
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Use stronger secret keys in production
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🚀 Next Steps
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Add password reset functionality
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Implement email verification
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Add user profile pages
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Create a simple blog system
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Deploy to Heroku or Render
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📚 Resources
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Flask Documentation
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SQLite Documentation
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Jinja2 Template Documentation
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