database signin and better styling

app.py

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+from flask import Flask, render_template, redirect, request, url_for
+from flask_sqlalchemy import SQLAlchemy
+from werkzeug.security import generate_password_hash, check_password_hash
+
+app = Flask(__name__)
+
+app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///accounts.db'
+app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
+app.secret_key = 'super_secret_session_encryption_key' 
+db = SQLAlchemy(app)
+
+class User(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    username = db.Column(db.String(80), unique=True, nullable=False)
+    email = db.Column(db.String(120), unique=True, nullable=False)
+    password_hash = db.Column(db.String(128), nullable=False)
+
+with app.app_context():
+    db.create_all()
+
+
+@app.route('/submit-form', methods=['POST'])
+def handle_submission():
+    form_username = request.form.get('username')
+    form_email = request.form.get('email')
+    form_password = request.form.get('password') # 1. Grab password from HTML
+    
+    # Check for duplicates
+    if User.query.filter_by(username=form_username).first():
+        return "<h3>Username taken!</h3>", 400
+    if User.query.filter_by(email=form_email).first():
+        return "<h3>Email already registered!</h3>", 400
+    
+    # 2. Hash the password into a secure scramble
+    hashed_password = generate_password_hash(form_password)
+    
+    # 3. Save the user with the scrambled hash
+    new_user = User(username=form_username, email=form_email, password_hash=hashed_password)
+    db.session.add(new_user)
+    db.session.commit()
+    
+    return redirect(url_for('success'))
+
+@app.route('/success')
+def success():
+    return "<h3>Data successfully saved to the database!</h3>"
+
+@app.route('/users')
+def view_users():
+    # Fetch all user records from the database
+    all_users = User.query.all()
+    
+    # Create a simple HTML table to display them nicely
+    html_output = "<h2>Registered Accounts</h2><table border='1' cellpadding='10'>"
+    html_output += "<tr><th>ID</th><th>Username</th><th>Email</th></tr>"
+    
+    for user in all_users:
+        html_output += f"<tr><td>{user.id}</td><td>{user.username}</td><td>{user.email}</td><td>{user.password_hash}</td></tr>"
+        
+    html_output += "</table>"
+    
+    # If the database is completely empty
+    if not all_users:
+        return "<h3>No accounts found in the database yet.</h3>"
+        
+    return html_output
+
+
+@app.route('/')
+def home():
+    return render_template('index.html')
+
+@app.route('/bivariate')
+def bivariate():
+    return render_template('bivariate.html')
+
+@app.route('/about')
+def about():
+    return render_template('about.html')
+
+@app.route('/signin')
+def signin():
+    return render_template('signin.html')
+
+@app.route('/signup')
+def signup():
+    return render_template('signup.html')
+
+if __name__ == '__main__':
+    app.run(debug=True)