Building an Expense Tracker in Python

import csv
from datetime import datetime

FILENAME = 'expenses.csv'

# Function to add an expense
def add_expense(date, amount, category, description):
    with open(FILENAME, mode='a', newline='') as file:
        writer = csv.writer(file)
        writer.writerow([date, amount, category, description])

# Function to read all expenses
def read_expenses():
    expenses = []
    try:
        with open(FILENAME, mode='r') as file:
            reader = csv.reader(file)
            for row in reader:
                expenses.append(row)
    except FileNotFoundError:
        pass
    return expenses

# Example usage
if __name__ == '__main__':
    date = input('Enter date (YYYY-MM-DD): ')
    amount = input('Enter amount: ')
    category = input('Enter category: ')
    description = input('Enter description: ')

    # Validate date format
    try:
        datetime.strptime(date, '%Y-%m-%d')
    except ValueError:
        print('Invalid date format. Use YYYY-MM-DD.')
        exit(1)

    # Validate amount
    try:
        amount = float(amount)
    except ValueError:
        print('Amount must be a number.')
        exit(1)

    add_expense(date, amount, category, description)
    print('Expense added successfully!')

    # Display all expenses
    expenses = read_expenses()
    print('\nAll Expenses:')
    for exp in expenses:
        print(f'Date: {exp[0]}, Amount: {exp[1]}, Category: {exp[2]}, Description: {exp[3]}')