app = Flask(__name__)

# Connect to the database
connection = pymysql.connect(host='localhost',
                            user='root',
                            password='1234',
                            db='mydb',
                            charset='utf8mb4',
                            cursorclass=pymysql.cursors.DictCursor)
@app.route('/')
def index():
    return render_template('signup.html')
@app.route('/signup', methods=['POST', 'GET' ])
def signup():
    cursor = connection.cursor()
    if request.method == 'POST':
        try:
            cursor.execute('''INSERT INTO users (user, fname, lname, email, pnum, password) VALUES (%s, %s, %s, %s, %s, %s)''')
            cursor.commit()
        finally:
            return render_template('login.html')


if __name__ == '__main__':
    app.run(debug=True)

<h1>Please Sign Up</h1>

<button onclick="document.getElementById('id01').style.display='block'"style="width:auto;">Sign Up</button>

<div id="id01" class="modal">
  <span onclick="document.getElementById('id01').style.display='none'" class="close" title="Close Modal">×</span>
  <form class="modal-content animate" action="/signup" method="POST">
    <div class="container">
      <label><b>Email</b></label>
      <input type="text" placeholder="Enter Email" name="email" required>

      <label><b>Password</b></label>
      <input type="password" placeholder="Enter Password" name="password" required>

        <label><b>user</b></label>
      <input type="text" placeholder="user" name="user" required>

        <label><b>First name</b></label>
      <input type="text" placeholder="First name" name="fname" required>


        <label><b>pnum</b></label>
      <input type="text" placeholder="Pnum" name="pnum" required>

        <label><b>Last name</b></label>
      <input type="text" placeholder="Last name" name="lname" required>
      <input type="checkbox" checked="checked"> Remember me
      <p>By creating an account you agree to our <a href="#">Terms & Privacy</a>.</p>

      <div class="clearfix">
        <button type="button" onclick="document.getElementById('id01').style.display='none'" class="cancelbtn">Cancel</button>
    <button type="submit" action="/Signup" method="POST" class="signupbtn">Sign Up</button>
  </div>
</div>

<script>
// Get the modal
var modal = document.getElementById('id01');

// When the user clicks anywhere outside of the modal, close it
window.onclick = function(event) {
    if (event.target == modal) {
        modal.style.display = "none";
    }
}
</script>