python-workspace/amortization.py at master · loust333/python-workspace · GitHub

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from decimal import *

def amortization(principal, rate, term):
    payment = pmt(principal, rate, term)
    begBal = principal
    print "Pmt no".rjust(6), '', 'Beg. bal.'.ljust(13), '',
    print "Payment".ljust(9), '', 'Principal'.ljust(9), '',
    print "Interest".ljust(9), '', 'End. bal.'.ljust(13)

    print ''.rjust(6, '-'), '', ''.ljust(13, '-'), '',
    print ''.rjust(9, '-'), ''.ljust(9, '-'), '',
    print ''.rjust(9, '-'), '', ''.ljust(13, '-'), ''

    for num in range(1, term + 1):
        interest = round(begBal * (rate / (12 * 100.0)), 2)
        applied = round(payment - interest, 2)
        endBal = round(begBal - applied, 2)

        print str(num).center(6), '',
        print '{0:,.2f}'.format(begBal).rjust(13), '',
        print '{0:,.2f}'.format(payment).rjust(9), '',
        print '{0:,.2f}'.format(applied).rjust(9), '',
        print '{0:,.2f}'.format(interest).rjust(9), '',
        print '{0:,.2f}'.format(endBal).rjust(13)
        begBal = endBal


def pmt(principal, rate, term):
    ratePerTwelve = rate/(12 * 100.0)
    result = principal * (ratePerTwelve / (1 - (1 + ratePerTwelve) ** (-term)))
    result = Decimal(result)
    result = round(result, 2)
    return result