MIT 6.00SC - Problem Set 1 - Problem 3

balance = float(raw_input('Enter the outstanding balance on your credit card: '))
annual_interest = float(raw_input('Enter the annual credit card interest rate as a decimal: '))
minimum_payment = balance/12.0
maximum_payment = (balance * (1 + (annual_interest / 12.0)) * 12.0) / 12.0
new_balance = balance

while balance != 0.0:
    monthly_payment = (minimum_payment + maximum_payment) / 2.0
    for month in range(1,13):
        new_balance = round((new_balance * (1 + (annual_interest / 12.0)) - monthly_payment),2)
        if new_balance <= 0.0:
            break
    if new_balance == 0.0:
        balance = new_balance
    elif new_balance > 0.0:
        minimum_payment = monthly_payment
        new_balance = balance
    else:
        maximum_payment = monthly_payment
        new_balance = balance

print 'RESULT'
print 'Monthly payment to pay off debt in 1 year:',round(monthly_payment,2)
print 'Number of months needed:',month
print 'Balance:',round(balance,2)