lab/expense_tracker.py

python

"""Week 1 lab (reference solution): CLI expense tracker.

Run:  uv run python expense_tracker.py

Try it yourself before reading this file.

"""

import json

from pathlib import Path

DATA_FILE = Path("expenses.json")

def load_expenses() -> list[dict]:

    if DATA_FILE.exists():

        return json.loads(DATA_FILE.read_text())

    return []

def save_expenses(expenses: list[dict]) -> None:

    DATA_FILE.write_text(json.dumps(expenses, indent=2, ensure_ascii=False))

def add_expense(expenses: list[dict]) -> None:

    try:

        amount = float(input("Amount (₹): "))

    except ValueError:

        print("Please enter a number.")

        return

    category = input("Category (food/travel/rent/other): ").strip().lower() or "other"

    note = input("Note: ").strip()

    expenses.append({"amount": amount, "category": category, "note": note})

    save_expenses(expenses)

    print("Saved.")

def list_expenses(expenses: list[dict]) -> None:

    if not expenses:

        print("No expenses yet.")

    for i, e in enumerate(expenses, start=1):

        print(f"{i:>3}. ₹{e['amount']:>10,.2f}  {e['category']:<8} {e['note']}")

def totals_by_category(expenses: list[dict]) -> dict[str, float]:

    totals: dict[str, float] = {}

    for e in expenses:

        totals[e["category"]] = totals.get(e["category"], 0) + e["amount"]

    return totals

def main() -> None:

    expenses = load_expenses()

    menu = "\n1) Add  2) List  3) Totals  4) Quit\n> "

    while True:

        choice = input(menu).strip()

        if choice == "1":

            add_expense(expenses)

        elif choice == "2":

            list_expenses(expenses)

        elif choice == "3":

            for category, total in sorted(totals_by_category(expenses).items()):

                print(f"{category:<8} ₹{total:,.2f}")

            print(f"{'TOTAL':<8} ₹{sum(e['amount'] for e in expenses):,.2f}")

        elif choice == "4":

            break

        else:

            print("Choose 1-4.")

if __name__ == "__main__":

    main()