Python ATM for Students

#!/usr/bin/python3

import sys
import sqlite3

'''
Information:
    Create a sqlite3 database named ATM.DB in the same folder as this file
    The create tables statements for the sqlite3 tables to make this program run are:
    CREATE TABLE accounts (user_id integer,account_number text PRIMARY KEY, balance decimal, interest_rate decimal, FOREIGN KEY(user_id) REFERENCES customers(user_id));
    CREATE TABLE customers (user_id integer PRIMARY KEY,first_name text, last_name text, pin text);
'''


def account_checker(cur, account_check):
    # Checks to see if the account is in the database
    cur.execute('select * from accounts where account_number ="{0}"'.format(account_check))
    # Returns either TRue of False if the account is in the database
    if len(list(cur)) < 1:
        return False
    else:
        return True


def pin_checker(cur, account_check, pin_check):
    # Checks to see if the PIN matches the account number
    cur.execute('''SELECT customers.pin, accounts.account_number
                   FROM customers
                   INNER JOIN accounts
                   ON customers.user_id=accounts.user_id
                   WHERE customers.pin = '{0}'
                   AND accounts.account_number = "{1}"'''.format(pin_check, account_check))
    # Returns either True or False if the PIN matches the account number
    if len(list(cur)) < 1:
        return False
    else:
        return True


def get_customer_name_by_acct(cur, valid_customer):
    # Retrieves the customers name given the account number
    cur.execute('''SELECT customers.first_name,customers.last_name
                   FROM customers
                   INNER JOIN accounts
                   ON customers.user_id=accounts.user_id
                   WHERE accounts.account_number = "{0}"'''.format(valid_customer))
    names = cur.fetchone()
    first_name, last_name = names[0], names[1]
    return first_name, last_name


def check_customer(cur):
    # Runs the login dialog and returns the validated account number
    try_number_acct = 0
    try_number_pin = 0
    while try_number_acct < 3 and try_number_pin < 3:
        account_check = input('[?] Enter you account number:\t')
        account_is_present = account_checker(cur, account_check)
        if account_is_present:
            while try_number_pin < 3:
                pin_check = input('[?] Enter your pin number:\t')
                pin_is_correct = pin_checker(cur, account_check, pin_check)
                if pin_is_correct:
                    print('[-] You have been authenticated')
                    return account_check
                else:
                    try_number_pin += 1
                    print('[!] Invalid PIN!!')
        else:
            try_number_acct += 1
            print('[!] Invalid account number!!')

    sys.exit('[!] Maximum Attempts Reached Exiting')


def withdraw_funds(cur, account_number, amount):
    cur.execute('SELECT balance FROM accounts WHERE account_number = "{0}"'.format(account_number))
    current_balance = cur.fetchone()[0]
    new_balance = float(current_balance) - float(amount)
    cur.execute('UPDATE accounts SET balance = {0} WHERE account_number = "{1}"'.format(new_balance, account_number))


def deposit_funds(cur, account_number, amount):
    cur.execute('SELECT balance FROM accounts WHERE account_number = "{0}"'.format(account_number))
    current_balance = cur.fetchone()[0]
    new_balance = float(current_balance) + float(amount)
    cur.execute('UPDATE accounts SET balance = {0} WHERE account_number = "{1}"'.format(new_balance, account_number))


def report_balance(cur, account_number):
    cur.execute('SELECT balance FROM accounts WHERE account_number = "{0}"'.format(account_number))
    return cur.fetchone()[0]


def report_interest_rate(cur, account_number):
    cur.execute('SELECT interest_rate FROM accounts WHERE account_number = "{0}"'.format(account_number))
    return cur.fetchone()[0]


def main():
    # Connect to the sqlite3 database
    conn = sqlite3.connect('ATM.DB')
    # Create the cursor (used to execute SQL commands
    cur = conn.cursor()
    # Authenticate our customer
    valid_account_number = check_customer(cur)
    # Get the customers name for the greeting
    customer_name = get_customer_name_by_acct(cur, valid_account_number)

    print('\n[-] Welcome to the Bank of Python {0} {1}\n'.format(customer_name[0], customer_name[1]))

    while True:
        choice = input('''
        [?] What is your choice?\n
        [1] Deposit\n
        [2] Withdraw\n
        [3] Display Balance\n
        [4] Display Interest Rate\n
        [5] Exit\n
        Enter choice>>\t''')

        choice = int(choice)

        if choice == 1:
            amount = float(input('[?] How much would you like to deposit?\t$'))
            deposit_funds(cur, valid_account_number, amount)
            conn.commit()
            print('\n[-] Your new balance is:',
                  '$' + str(report_balance(cur, valid_account_number)))

        elif choice == 2:
            amount = float(input('[?] How much would you like to withdraw?\t$'))
            withdraw_funds(cur, valid_account_number, amount)
            conn.commit()
            print('\n[-] Your new balance is:',
                  '$' + str(report_balance(cur, valid_account_number)))

        elif choice == 3:
            print('\n[-] Your balance is:',
                  '$' + str(report_balance(cur, valid_account_number)))

        elif choice == 4:
            print('\n[-] Your interest rate is:',
                  str(report_interest_rate(cur, valid_account_number)) + '%')

        elif choice == 5:
            sys.exit('\n[-] Good Bye!')

        else:
            sys.exit('\n[!] Exiting Program')


if __name__ == '__main__':
    main()