app.py

from flask import Flask, render_template, request, redirect, url_for, session
from flask_mysqldb import MySQL
import re
app=Flask(__name__)

app.secret_key = 'ARUNkumar'

# database connection details 
app.config['MYSQL_HOST'] = ' '
app.config['MYSQL_USER'] = ' '
app.config['MYSQL_PASSWORD'] = ' '
app.config['MYSQL_DB'] = ' '

# Intialize MySQL
mysql = MySQL(app)
@app.route('/', methods=['GET', 'POST'])
def login():
    msg = ''
    # Check if "username" and "password" POST requests exist (user submitted form)
    if request.method == 'POST' and 'username' in request.form and 'password' in request.form:
        # Create variables for easy access
        username = request.form['username']
        password = request.form['password']
        cur =mysql.connection.cursor()

        cur.execute('SELECT * FROM accounts WHERE username = %s AND password = %s', [username, password])
        # Fetch one record and return result
        account = cur.fetchone()
        print(account)
        if account:
            session['loggedin'] = True
            session['id'] = account[0]
            session['username'] = account[1]
            return redirect(url_for('home'))

        else:
            # Account doesnt exist or username/password incorrect
            msg = 'Incorrect username/password!'
    return render_template('index.html', msg=msg)
@app.route('/logout.html')
def logout():
   session.pop('loggedin', None)
   session.pop('id', None)
   session.pop('username', None)
   return redirect(url_for('login'))
@app.route('/register.html', methods=['GET', 'POST'])
def register():
    # Output message if something goes wrong...
    msg = ''
    # Check if "username", "password" and "email" POST requests exist (user submitted form)
    if request.method == 'POST' and 'username' in request.form and 'password' in request.form and 'email' in request.form:
        # Create variables for easy access
        username = request.form['username']
        password = request.form['password']
        email = request.form['email']
         # Check if account exists using MySQL
        cur = mysql.connection.cursor()

        cur.execute('SELECT * FROM accounts WHERE username = %s', [username])
        account = cur.fetchone()
        # If account exists show error and validation checks
        if account:
            msg = 'Account already exists!'
        elif not re.match(r'[^@]+@[^@]+\.[^@]+', email):
            msg = 'Invalid email address!'
        elif not re.match(r'[A-Za-z0-9]+', username):
            msg = 'Username must contain only characters and numbers!'
        elif not username or not password or not email:
            msg = 'Please fill out the form!'
        else:
            # Account doesnt exists and the form data is valid, now insert new account into accounts table
            cur.execute('INSERT INTO accounts VALUES (NULL, %s, %s, %s)', [username, password, email])
            mysql.connection.commit()
            msg = 'You have successfully registered!'
    elif request.method == 'POST':
        # Form is empty
        msg = 'Please fill out the form!'
    # Show registration form with message (if any)
    return render_template('register.html', msg=msg)
@app.route('/home.html')
def home():
    # Check if user is loggedin
    if 'loggedin' in session:
        # User is loggedin show them the home page
        return render_template('home.html', username=session['username'])
    # User is not loggedin redirect to login page
    return redirect(url_for('login.html'))
@app.route('/profile.html')
def profile():
    # Check if user is loggedin
    if 'loggedin' in session:
        cur =mysql.connection.cursor()

        cur.execute('SELECT * FROM accounts WHERE id = %s', [session['id']])
        account = cur.fetchone()
        # Show the profile page with account info
        return render_template('profile.html', account=account)
    # User is not loggedin redirect to login page
    return redirect(url_for('login.html'))
if __name__=='__main__':
   app.run(debug=True)