ATM in Python. How can I connect the database in the first code to the transaction in the second code? read body

Question

I have written 2 pieces of code.

1. login and authentication

 def register():
    db = open("database.txt","r")
    account_number= input("Enter your Account Number: ")
    pin = input("Create a 4-digit pin: ")
    pin1 = input("Confirm Pin: ")
    d = []
    f = []
    for i in db:
        a,b = i.split(", ")
        b = b.strip()
        d.append(a)
        f.append(b)
    data = dict(zip(d,f))
    print(data)

    if pin != pin1:
        print("Pins don't match, try again!")
        register()
    else:
        if len(pin) != 4:
            print("Pin is not 4-digit. Pin must be 4-digit")
            register()
        elif account_number in d:
            print("account number already exists")
            register()
        else:
            db = open("database.txt","a")
            db.write(account_number+", "+pin+", 0" "\n")
            print("Success!")
    db.close()


def access():
    db = open("database.txt", "r")
    account_number = input("Enter your account number: ")
    pin = input("Enter your pin: ")

    if not len(account_number or pin)<1:
        d = []
        f = []
        for i in db:
            a, b = i.split(", ")
            b = b.strip()
            d.append(a)
            f.append(b)
        data = dict(zip(d, f))

        try:
            if data[account_number]:
                try:
                    if pin== data[account_number]:
                        print("Login Success")
                    else:
                        print("Pin or Account Number Incorrect")
                except:
                    print("Pin or Account Number Incorrect")
            else:
                print("Account Number doesn't exist")
        except:
            print("Login error")
    else:
        print("Please Enter your login credentials")
    db.close()
def home(option = None):
    option = input("Login | Signup: ")
    if option == "Login":
        access()
    elif option == "Signup":
        register()
    else:
        print("Please choose an option")
home()

2. money transactions

choice = 0
while choice != 4:
      print("\n\n**** Menu *****")
      print("1 -- balance")
      print("2 == deposit")
      print("3 == withdraw")
      print("4 == cancel\n")

      choice=int(input("\nEnter your option:\n"))
      if choice==1:
             print("Balance = ", +balance)
      elif choice==2:
           dep=int(input("Enter your deposit: "))
           balance+=dep
           print("\n deposited amount: " , +dep)
           print("balance = ", +balance)
      elif choice==3:
           wit=int(input("Enter the amount to withdraw: "))
           balance -= wit
           print("\n withdrawn amount: " , +wit)
           print("balance =", +balance)
      elif choice ==4:
           print('Session ended,goodbye.')
      else:
           print("Invalid Entry")

The first code stores an account number and pin in the database. The balance should be 0 automatically for a new account. What can I do to automatically set the balance to 0 and store it in the database?

What should I do to only allow numerical values?

How can I connect the second code to the database in the first code?

Answer 1

Your first question is how you can automatically create an account with a balance of 0. Unless I am mistaken and the 0 is something else you are already doing that with this line: db.write(account_number+", "+pin+", 0" "\n").

I don't know what issue you are encountering but I could see a potential problem because you are opening the database in write('w') mode and then open it in append('a') mode. You can't do both at the same time, you have to close it beforehand.

Your second question is a bit more complicated to answer, you'll either have to create classes or structure your program differently.

To make it easy for ourselves we'll just load the database into memory. This is most of the logic already, implement your menu in the main loop:

DB_FILE = "database.txt"

db = {}
with open(DB_FILE, 'r') as f:
    db_lines = f.read().splitlines()

for line in db_lines:
    acc_num, pin, balance = line.split()
    db[acc_num] = {'pin': pin, 'balance': int(balance)}


def update_db():
    with open(DB_FILE, 'w') as f:
        for acc_num, data in db.items():
            f.write(acc_num + " " + data['pin'] + " " + str(data['balance']))


def register(acc_num, pin):
    db[acc_num] = {'pin' : pin, 'balance': 0}
    update_db()

def access(acc_num, pin):
    if db[acc_num]['pin'] == pin:
        return True
    return False

def withdraw(acc_num, amount):
    db[acc_num]['balance'] -= amount
    update_db()


def deposit(acc_num, amount):
    db[acc_num]['balance'] += amount
    update_db()

login = False
while True:
    if not login:
        choice = input('register or access')
        if choice == 'access':
            acc_num = input('accnum')
            pin = input('pin')
            if access(acc_num, pin):
                login = True
        elif choice == 'register':
            # get acc num + pin
            register(acc_num, pin)
            login = True   
    else:
        # withdraw and deposit