Running a flask app locally with MySQL install in Xampp (Lampp - Linux Users), this method works fine.

app.py

from flask import Flask, render_template, redirect, session, request, url_for
import pymysql
import secret

# Initialize the flask library
app = Flask(__name__)
# create secret key to use for sessions
app.secret_key = "JustMakeThisEndInWeirdLines123@#!IThinkThisIsFine"

# create a connection to the mysql (phpMyAdmin) server
# you can create a secret.py file or just replace 
connection = pymysql.connect(host=secret.dbHost,
                             user=secret.dbUser,
                             passwd=secret.dbPass,
                             database=secret.dbName)


# cursor = connection.cursor()


# Login route
@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:
        # Get the passed values
        username = request.form['username']
        password = request.form['password']

        with connection.cursor() as cursor:
            # check if the logged details do exist in the database
            check_user_existence = "SELECT * FROM users WHERE username = '" + username + "' AND password = '" + password + "'; "
            cursor.execute(check_user_existence)
            connection.commit()
            # fetch the one record from the db
            user = cursor.fetchone()
            # check if the sql returns true or false
            if user:
                # create session variables
                session['isLoggedIn'] = True
                # pymysql accepts int, so have to know the column number
                session['id'] = user[0]
                session['username'] = user[2]
                # redirect to home page

                return redirect(url_for('home'))
            else:
                # User does not exist or wrong username/password provided
                msg = "Wrong username/Password"

    return render_template("login.html", msg=msg)


# Logout script
@app.route("/logout")
def logout():
    # kill/terminate the current session, this will log the user out of the application
    # session.pop() takes two arguments, one is for the session name and the other one is to elimate
    session.pop('isLoggedIn', None)
    session.pop('id', None)
    session.pop('username', None)

    return redirect(url_for('login'))


# Home/default route
@app.route("/home")
def home():
    # check if the session is active
    if 'isLoggedIn' in session:
        # query for totals cases

        with connection.cursor() as cursor:
            select_totals = "SELECT * FROM cumulative_totals;"

            cursor.execute(select_totals)
            # connection is not autocommit by default. So you must commit to save
            # your changes.
            connection.commit()
            # fetch all the totals in the database
            # Bug Query doesn't pick new values unless the application is restarted, not sure if its the
            cumulative_totals = cursor.fetchone()
            print(cumulative_totals)
            # username is logged in, show the home page,
            # cumulative_totals passes the result from the query
            return render_template("index.html", username=session['username'], cumulative_totals=cumulative_totals)

    return redirect(url_for('login'))


@app.route("/addNew")
def add_new():
    if 'isLoggedIn' in session:
        return render_template("AddNew.html")

    return render_template("login.html")


# entry point for the application
if __name__ == "__main__":
    # Set the port for the application, this is only for development
    # turn debug on in development
    app.run(port=5004, debug=True)