Bank Management System

A console-based Bank Management System built with Python using Object-Oriented Programming (OOP) principles. Unlike a simple ATM simulator, this project models real banking operations — account opening, loans, checkbooks, interest, and admin oversight — with secure PIN hashing, brute-force protection, JSON-based data persistence, and a modular package structure.

---

Features

• Admin Panel:

  • Secure Admin Login
  • Open New Account (auto-assigned account number, Savings/Current)
  • Close Account (blocked if balance, loan, or pending requests exist)
  • Freeze / Unfreeze Account (also clears a PIN-lockout on reactivation)
  • Manage Loan Requests (Approve / Reject)
  • Manage Checkbook Requests (Approve / Reject)
  • View Complete Bank Report (deposits, loans, transactions, per-account overview)
  • Apply Monthly Interest to All Savings Accounts

• Customer System:

  • Login (Account Number + PIN)
  • Check Balance (with account type, status, and pending requests shown)
  • Deposit / Withdraw Money
  • Change PIN
  • Cash Statement (last 30 days)
  • Mini Statement (last 5 transactions)
  • Transfer Money (with self-transfer and limit checks)
  • Apply for Loan / Return Loan
  • Request Checkbook

• Data & Security Features:

  • SHA-256 PIN Hashing (no plaintext PINs stored)
  • 3-Attempt PIN Lockout — account automatically freezes after 3 consecutive incorrect PIN entries, and can only be reactivated by an admin
  • Persistent JSON Storage with backward-compatible loading (handles both legacy and current data formats)
  • Auto-generated Transaction Receipts (.txt, saved under receipts/)
  • Per-transaction limit (Rs. 100,000) and daily withdrawal limit (Rs. 200,000)
  • Savings minimum balance (Rs. 2,000) vs. Current account overdraft allowance (Rs. 50,000)
  • Account Freeze/Unfreeze (frozen accounts blocked from all transactions)
  • Full transaction history logging with date and time
  • Input validation and exception handling throughout

---

Technologies Used

• Python 3 (Object-Oriented Programming)
• JSON Module (Data persistence)
• hashlib (SHA-256 PIN hashing)
• pathlib (File and directory handling)
• Datetime Module (Timestamps, interest cycles, statement filtering)

---

Project Structure

Bank-Management-System/
│
├── data/
│   └── accounts.json          # Persistent JSON account records (gitignored)
│
├── receipts/                  # Auto-generated transaction receipts (gitignored)
│   ├── general/
│   ├── sent/
│   └── received/
│
├── src/                       # Source code package
│   ├── __init__.py
│   ├── models.py               # BankAccount class — data, validation, and account-level operations
│   ├── manager.py               # BankManager class — persistence, admin operations, multi-account logic
│   └── UI.py                    # CLI menus and display formatting
│
├── .gitignore                 # Excludes __pycache__, receipts, and local data
├── main.py                    # Application entry point
└── README.md

Note: data/accounts.json is created automatically on first run with sample accounts. It stores account records and full transaction history locally, and is excluded from the repository via .gitignore.

---

How to Run

Clone the repository

git clone https://github.com/osaid400/Bank-Management-System.git

Move into the project folder

cd Bank-Management-System

Run the program

python main.py

---

Example Outputs

Main Menu

============================================================
              WELCOME TO BANK MANAGEMENT SYSTEM
============================================================
1. Customer Login
2. Admin Login
0. Exit
------------------------------------------------------------

PIN Lockout in Action

Enter Account Number: 3012
Enter 4-digit PIN: 0000
Login Failed: Incorrect PIN! Remaining attempts: 2

Enter Account Number: 3012
Enter 4-digit PIN: 0000
Login Failed: Incorrect PIN! Remaining attempts: 1

Enter Account Number: 3012
Enter 4-digit PIN: 0000
Login Failed: Account FROZEN due to 3 consecutive wrong PIN attempts! Contact Admin.

Customer Menu

============================================================
                     Welcome Back, Abdullah
============================================================
1. Check Balance
2. Deposit Money
3. Withdraw Money
4. Change Pin
5. Cash Statement (30 Days)
6. Transfer Money
7. Mini Statement
8. Request Checkbook
9. Apply Loan
10. Return Loan
11. Logout
0. Back to Main Menu
------------------------------------------------------------

Apply for a Loan

Enter choice: 9
Enter loan amount to apply for: 50000

Loan application of Rs. 50,000.00 submitted! Awaiting admin approval.

Admin Panel — Manage Loan Requests

--- PENDING LOAN REQUESTS ---
Account: 3012 | Name: Abdullah | Requested: Rs. 50,000.00

Enter account number to process: 3012
Type 'A' to Approve or 'R' to Reject: A

Loan of Rs. 50,000.00 approved for Abdullah.

Admin Panel — Bank Report

================================================================================
                 COMPREHENSIVE BANK FINANCIAL & ACTIVITY REPORT
================================================================================

---------------------------- GLOBAL FINANCIAL SUMMARY --------------------------
Total Customers                : 10
Active Accounts                : 9
Frozen Accounts                : 1
Total Bank Deposits            : Rs. 292,865.31
Total Approved Loans           : Rs. 50,000.00
Total Pending Loans Amount     : Rs. 0.00
Pending Checkbook Requests     : 1
Total System Transactions      : 34

------------------------ ALL CUSTOMER ACCOUNTS OVERVIEW ------------------------
Acc No   Name            Type       Status     Balance        Active Loan
--------------------------------------------------------------------------------
3011     Ali             Savings    ACTIVE     Rs.15,188      Rs.0
3012     Abdullah        Savings    FROZEN     Rs.23,795      Rs.50,000
================================================================================

Transaction Receipt (.txt output)

============================================================
                BANK MANAGEMENT SYSTEM - RECEIPT
============================================================
Account Holder : Abdullah
Account Number : 3012
Account Type   : Savings
Date           : 2026-08-10
Time           : 09:47:17
Transaction    : Deposit
Amount         : Rs. 5,000.00
Description    : Cash Deposit
Current Balance: Rs. 28,795.00
============================================================

---

Concepts Covered

• Object-Oriented Programming (OOP): Class design and encapsulation (BankAccount, BankManager), with private attributes (__balance, __pin_hash) accessed only through class-defined methods.
• CRUD Operations: Full account lifecycle — open, update (via transactions), close.
• JSON Data Serialization: Persistent, backward-compatible storage via to_dict() / from_dict(), handling both legacy and current data formats safely.
• Security: SHA-256 PIN hashing (no plaintext PINs stored) and a 3-attempt lockout to slow down PIN-guessing.
• Business Logic & Validation: Multi-step rules for withdrawals (per-transaction and daily limits, account-type-based minimum balance/overdraft), loans (eligibility, request-then-approve workflow), and account closure (blocked while pending requests exist).
• Admin/Customer Role Separation: Distinct menus and permissions — customers manage their own account; admins manage the whole bank.
• Modules & Packages: Code organized into a src/ package (models.py, manager.py, UI.py), separating data, business logic, and presentation, with main.py as the entry point outside the package.
• Defensive Programming: Input validation and exception handling (try/except/raise) across all menus and operations.
• Date & Time Handling: Interest cycles, transaction timestamps, and 30-day statement filtering via datetime.

---

How Loans & Checkbooks Work

• Customers apply for a loan or checkbook — this creates a pending request, it does not immediately grant anything.
• Admins review pending requests in the Admin Panel and approve or reject them.
• Only on approval does a loan disburse funds (via a dedicated receive_loan_disbursement() method that keeps the balance update inside the BankAccount class) or a checkbook get marked Approved.
• This mirrors how a real bank processes these requests — no self-service approval.

How the PIN Lockout Works

• Every failed PIN attempt increments a per-account counter.
• A correct PIN resets the counter to zero.
• On the 3rd consecutive failure, the account is automatically frozen (same is_active flag admins use), the reason is recorded distinctly in the transaction log ("Account Frozen: 3 Failed PIN Attempts"), and the account can only be reactivated by an admin.
• Reactivating an account via the Admin Panel also resets the failed-attempt counter to zero.

---

Future Improvements

• Salted password hashing (current hashing is unsalted)
• Move admin credentials out of source code (environment variables or a config file)
• SQLite or PostgreSQL integration replacing JSON persistence
• RESTful API backend (FastAPI/Flask)
• Graphical User Interface (Tkinter)
• EMI-style scheduled loan repayment instead of manual lump-sum repayment
• Multi-currency support

---

Learning Outcomes

This project helped me practice and solidify key software engineering concepts:

• Encapsulation in practice: Keeping balance and PIN mutations strictly inside BankAccount, and catching (then fixing) a real bug where manager code briefly reached into a private attribute directly from outside the class.
• Designing approval workflows: Separating "request" from "approval" for loans and checkbooks, closer to how real banking systems operate.
• Backward-compatible persistence: Writing a from_dict() that safely loads both older and newer JSON formats without crashing.
• Business rule design: Translating real-world constraints (overdraft limits, minimum balances, daily withdrawal caps, brute-force lockouts) into validated code.
• Modular project structure: Splitting a single-file project into a models / manager / UI / main package, and understanding why each piece of logic belongs where it does.

---

Author

Muhammad Abdullah Farooq

GitHub: https://github.com/osaid400