🏧 ATM Simulator (Python)

A console-based ATM simulator written in Python using core programming concepts: functions, loops, conditionals, input validation, and in-memory data handling.

📘 Project Overview

This program simulates a realistic ATM system for registered bank account holders. Each user can securely log in using their account number and PIN, perform multiple banking operations, and receive a detailed receipt at the end of the session.

All account data is stored in Python lists and dictionaries during runtime. No files, databases, or external libraries are used.

🧰 Technologies Used

• Python (functions, loops, conditionals)
• Lists and dictionaries for account storage
• Input validation using string methods
• No external libraries required

📂 Program Execution Flow

1. Main menu is displayed with options to:
   • Perform an ATM operation
   • Exit the program
2. User enters an account number to log in.
3. The system searches for the account in stored records.
4. User enters PIN with a maximum of three attempts.
5. On successful authentication, the ATM menu is displayed.
6. All transactions are tracked during the session.
7. A receipt is generated before exiting the session.

🔐 Login & PIN System

• Login requires a valid account number and PIN.
• PIN must contain only digits.
• Maximum of three incorrect attempts allowed.
• Account access is denied after exceeding attempts.

👤 Registered User Accounts

The system maintains predefined bank accounts in memory:

accounts = [
  {
    "name": "Ahmed",
    "account_no": "49217385",
    "pin": "1234",
    "balance": 12000,
    "initial_balance": 12000
  },
  ...
]

• Accounts are searched by account number.
• PINs are stored as strings for validation consistency.
• Each account tracks its initial balance for receipt generation.

📋 ATM Menu Options

Once logged in, the account holder can:

1. View Balance
2. Deposit Money
3. Withdraw Money
4. Pay Utility Bills
5. Change ATM PIN
6. Exit Session

💰 Banking Features

• Balance Inquiry: Displays current balance and logs the action.
• Deposit: Allows only positive numeric amounts.
• Withdrawal: Prevents overdrawing the account.
• Utility Bill Payments:
  • Electricity
  • Gas
  • Water
  • Internet / WiFi
  • Telephone / Mobile
• PIN Change: Requires old PIN verification and confirmation.

🧾 Transaction Receipt

At the end of each session, a receipt is automatically generated showing:

• Account holder name
• Starting balance
• Closing balance
• Complete transaction history

If no actions were performed, the receipt clearly indicates this.

🧠 Learning Objectives

• Design menu-driven console applications.
• Implement secure authentication logic.
• Track and manage session-based state.
• Apply input validation and error handling.
• Simulate real-world ATM workflows using Python.

✨ Thank You for Visiting! ✨

Feel free to explore, refactor, and extend this ATM simulator to enhance your Python programming skills.