amort/amort.py

def generate_amortization_schedule(principal, interest_rate, loan_term, one_time_payment=None):
    # Convert interest rate to decimal and calculate periodic interest rate
    monthly_interest_rate = interest_rate / 12 / 100

    # Calculate the number of monthly payments
    num_payments = loan_term * 12

    # Calculate the fixed monthly payment using the amortization formula
    monthly_payment = (principal * monthly_interest_rate) / (1 - (1 + monthly_interest_rate) ** -num_payments)

    # Initialize variables
    remaining_balance = principal
    amortization_schedule = []

    for payment_number in range(1, num_payments + 1):
        # Calculate interest for the current period
        interest_payment = remaining_balance * monthly_interest_rate

        # Calculate principal payment
        principal_payment = monthly_payment - interest_payment

        # Apply one-time payment if provided
        if one_time_payment and payment_number == one_time_payment['payment_number']:
            principal_payment += one_time_payment['amount']
            remaining_balance -= one_time_payment['amount']

        # Update remaining balance
        remaining_balance -= principal_payment

        # Create a dictionary with payment details and add it to the amortization schedule
        payment_details = {
            'Payment Number': payment_number,
            'Payment Amount': monthly_payment,
            'Interest Payment': interest_payment,
            'Principal Payment': principal_payment,
            'Remaining Balance': remaining_balance
        }
        amortization_schedule.append(payment_details)

    return amortization_schedule

# Example usage
principal = 100000
interest_rate = 5.0
loan_term = 30

one_time_payment = {
    'payment_number': 13,
    'amount': 5000
}

schedule = generate_amortization_schedule(principal, interest_rate, loan_term, one_time_payment)

# Display the amortization schedule
for payment in schedule:
    print(payment)