🏧 ATM Operation System — Python

A console-based ATM simulation built with Python that demonstrates custom exception handling, modular programming, and real-world banking logic.

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📁 Project Structure

ATM-Operation-System/ ├── ATMException.py # Custom Exception Classes ├── ATMMenu.py # ATM Menu Display ├── ATMOperation.py # Core Banking Operations └── ATMMainProgram.py # Main Driver Program

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⚙️ Features

• 💰 Deposit — Add funds to your account with input validation
• 🏧 Withdraw — Withdraw funds with minimum balance enforcement
• 📊 Balance Inquiry — Check current available balance
• 🚪 Exit — Safely exit the ATM session
• 🔒 Minimum Balance — Rs.500 must be maintained at all times
• ⚠️ Custom Exceptions — Meaningful error messages for every case
• 🔁 Continuous Loop — Runs until user chooses to exit

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🧩 Module Breakdown

1. ATMException.py

Defines three custom exception classes:

Exception	Triggered When
DepositError	Deposit amount is zero or negative
WithdrawError	Withdraw amount is zero or negative
InsufficientAmountError	Withdrawal exceeds balance minus Rs.500

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2. ATMMenu.py

Displays the ATM menu with 4 options:

• 1 → Deposit
• 2 → Withdraw
• 3 → Balance Inquiry
• 4 → Exit

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3. ATMOperation.py

Contains three core functions:

deposit()

• Takes deposit amount as input
• Raises DepositError if amount ≤ 0
• Adds amount to global balance

withdraw()

• Takes withdrawal amount as input
• Raises WithdrawError if amount ≤ 0
• Raises InsufficientAmountError if (withdraw + 500) > balance
• Deducts amount from global balance

balance_inquiry()

• Displays current available balance

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4. ATMMainProgram.py

• Main driver using while True loop
• Uses match-case (Python 3.10+) for menu selection
• Handles all exceptions gracefully with user-friendly messages

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🚀 How to Run

Step 1 — Clone the repository git clone https://github.com/Biswojit02/ATM-Operation-System.git

Step 2 — Navigate to the folder cd ATM-Operation-System

Step 3 — Run the main program python ATMMainProgram.py

⚠️ Requires Python 3.10+ (for match-case support)

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⚠️ Exception Handling Coverage

Scenario	Exception Handled
Deposit amount = 0 or negative	DepositError
Withdraw amount = 0 or negative	WithdrawError
Withdraw exceeds balance - 500	InsufficientAmountError
Entering letters for amount	ValueError
Entering letters for menu choice	ValueError
Invalid menu choice number	case _ default

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🛠️ Tech Stack

• Language — Python 3.10+
• Concepts Used — Custom Exceptions, Modular Programming, Global Variables, Match-Case, Exception Handling, Loops

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📌 Key Concepts Demonstrated

• ✅ Custom Exception Classes (Exception subclassing)
• ✅ Modular code split across multiple files
• ✅ match-case statement (Python 3.10+)
• ✅ global variable usage
• ✅ Nested try-except blocks
• ✅ Real-world banking constraint (minimum balance)
• ✅ Input validation for all user entries

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📜 License

This project is open source and available under the MIT License.