loan_interest.md

./loan_interest.py -y 30 20 15 10 5 3 2 1 -r 3.0 -g 3

贷款年限: 30年

利率	月供	等额本息利息	等额本金利息	利息差
3.00	0.4216%	51.7775%	45.1250%	6.6525%
3.10	0.4270%	53.7259%	46.6292%	7.0967%
3.20	0.4325%	55.6881%	48.1333%	7.5547%
3.30	0.4380%	57.6639%	49.6375%	8.0264%
3.40	0.4435%	59.6532%	51.1417%	8.5116%
3.50	0.4490%	61.6561%	52.6458%	9.0103%
3.60	0.4546%	63.6723%	54.1500%	9.5223%
3.70	0.4603%	65.7019%	55.6542%	10.0477%
3.80	0.4660%	67.7446%	57.1583%	10.5863%
3.90	0.4717%	69.8006%	58.6625%	11.1381%
4.00	0.4774%	71.8695%	60.1667%	11.7028%
4.10	0.4832%	73.9514%	61.6708%	12.2806%
4.20	0.4890%	76.0462%	63.1750%	12.8712%
4.30	0.4949%	78.1537%	64.6792%	13.4746%
4.40	0.5008%	80.2739%	66.1833%	14.0906%
4.50	0.5067%	82.4067%	67.6875%	14.7192%
4.60	0.5126%	84.5520%	69.1917%	15.3603%
4.70	0.5186%	86.7096%	70.6958%	16.0138%
4.80	0.5247%	88.8795%	72.2000%	16.6795%
4.90	0.5307%	91.0616%	73.7042%	17.3575%
5.00	0.5368%	93.2558%	75.2083%	18.0475%
5.10	0.5429%	95.4619%	76.7125%	18.7494%
5.20	0.5491%	97.6799%	78.2167%	19.4633%
5.30	0.5553%	99.9097%	79.7208%	20.1888%
5.40	0.5615%	102.1511%	81.2250%	20.9261%
5.50	0.5678%	104.4040%	82.7292%	21.6749%
5.60	0.5741%	106.6684%	84.2333%	22.4351%
5.70	0.5804%	108.9442%	85.7375%	23.2067%
5.80	0.5868%	111.2311%	87.2417%	23.9894%
5.90	0.5931%	113.5291%	88.7458%	24.7833%
6.00	0.5996%	115.8382%	90.2500%	25.5882%

贷款年限: 20年

利率	月供	等额本息利息	等额本金利息	利息差
3.00	0.5546%	33.1034%	30.1250%	2.9784%
3.10	0.5596%	34.3081%	31.1292%	3.1789%
3.20	0.5647%	35.5191%	32.1333%	3.3857%
3.30	0.5697%	36.7365%	33.1375%	3.5990%
3.40	0.5748%	37.9602%	34.1417%	3.8186%
3.50	0.5800%	39.1903%	35.1458%	4.0445%
3.60	0.5851%	40.4268%	36.1500%	4.2768%
3.70	0.5903%	41.6695%	37.1542%	4.5153%
3.80	0.5955%	42.9185%	38.1583%	4.7602%
3.90	0.6007%	44.1738%	39.1625%	5.0113%
4.00	0.6060%	45.4353%	40.1667%	5.2686%
4.10	0.6113%	46.7030%	41.1708%	5.5322%
4.20	0.6166%	47.9770%	42.1750%	5.8020%
4.30	0.6219%	49.2571%	43.1792%	6.0779%
4.40	0.6273%	50.5434%	44.1833%	6.3601%
4.50	0.6326%	51.8359%	45.1875%	6.6484%
4.60	0.6381%	53.1344%	46.1917%	6.9427%
4.70	0.6435%	54.4391%	47.1958%	7.2432%
4.80	0.6490%	55.7498%	48.2000%	7.5498%
4.90	0.6544%	57.0666%	49.2042%	7.8624%
5.00	0.6600%	58.3894%	50.2083%	8.1810%
5.10	0.6655%	59.7182%	51.2125%	8.5057%
5.20	0.6711%	61.0530%	52.2167%	8.8363%
5.30	0.6766%	62.3937%	53.2208%	9.1729%
5.40	0.6823%	63.7404%	54.2250%	9.5154%
5.50	0.6879%	65.0930%	55.2292%	9.8638%
5.60	0.6935%	66.4514%	56.2333%	10.2181%
5.70	0.6992%	67.8157%	57.2375%	10.5782%
5.80	0.7049%	69.1858%	58.2417%	10.9442%
5.90	0.7107%	70.5618%	59.2458%	11.3159%
6.00	0.7164%	71.9435%	60.2500%	11.6935%

贷款年限: 15年

利率	月供	等额本息利息	等额本金利息	利息差
3.00	0.6906%	24.3047%	22.6250%	1.6797%
3.10	0.6954%	25.1722%	23.3792%	1.7931%
3.20	0.7002%	26.0434%	24.1333%	1.9101%
3.30	0.7051%	26.9183%	24.8875%	2.0308%
3.40	0.7100%	27.7967%	25.6417%	2.1551%
3.50	0.7149%	28.6789%	26.3958%	2.2830%
3.60	0.7198%	29.5646%	27.1500%	2.4146%
3.70	0.7247%	30.4540%	27.9042%	2.5498%
3.80	0.7297%	31.3470%	28.6583%	2.6887%
3.90	0.7347%	32.2436%	29.4125%	2.8311%
4.00	0.7397%	33.1438%	30.1667%	2.9772%
4.10	0.7447%	34.0476%	30.9208%	3.1268%
4.20	0.7498%	34.9551%	31.6750%	3.2801%
4.30	0.7548%	35.8661%	32.4292%	3.4369%
4.40	0.7599%	36.7806%	33.1833%	3.5973%
4.50	0.7650%	37.6988%	33.9375%	3.7613%
4.60	0.7701%	38.6205%	34.6917%	3.9288%
4.70	0.7753%	39.5458%	35.4458%	4.0999%
4.80	0.7804%	40.4746%	36.2000%	4.2746%
4.90	0.7856%	41.4070%	36.9542%	4.4528%
5.00	0.7908%	42.3429%	37.7083%	4.6345%
5.10	0.7960%	43.2823%	38.4625%	4.8198%
5.20	0.8013%	44.2252%	39.2167%	5.0085%
5.30	0.8065%	45.1716%	39.9708%	5.2008%
5.40	0.8118%	46.1216%	40.7250%	5.3966%
5.50	0.8171%	47.0750%	41.4792%	5.5959%
5.60	0.8224%	48.0319%	42.2333%	5.7986%
5.70	0.8277%	48.9923%	42.9875%	6.0048%
5.80	0.8331%	49.9562%	43.7417%	6.2145%
5.90	0.8385%	50.9235%	44.4958%	6.4276%
6.00	0.8439%	51.8942%	45.2500%	6.6442%

贷款年限: 10年

利率	月供	等额本息利息	等额本金利息	利息差
3.00	0.9656%	15.8729%	15.1250%	0.7479%
3.10	0.9702%	16.4276%	15.6292%	0.7985%
3.20	0.9749%	16.9840%	16.1333%	0.8507%
3.30	0.9795%	17.5421%	16.6375%	0.9046%
3.40	0.9842%	18.1017%	17.1417%	0.9601%
3.50	0.9889%	18.6630%	17.6458%	1.0172%
3.60	0.9935%	19.2260%	18.1500%	1.0760%
3.70	0.9983%	19.7906%	18.6542%	1.1364%
3.80	1.0030%	20.3568%	19.1583%	1.1985%
3.90	1.0077%	20.9247%	19.6625%	1.2622%
4.00	1.0125%	21.4942%	20.1667%	1.3275%
4.10	1.0172%	22.0653%	20.6708%	1.3945%
4.20	1.0220%	22.6381%	21.1750%	1.4631%
4.30	1.0268%	23.2124%	21.6792%	1.5333%
4.40	1.0316%	23.7885%	22.1833%	1.6051%
4.50	1.0364%	24.3661%	22.6875%	1.6786%
4.60	1.0412%	24.9454%	23.1917%	1.7537%
4.70	1.0461%	25.5262%	23.6958%	1.8304%
4.80	1.0509%	26.1087%	24.2000%	1.9087%
4.90	1.0558%	26.6929%	24.7042%	1.9887%
5.00	1.0607%	27.2786%	25.2083%	2.0703%
5.10	1.0655%	27.8660%	25.7125%	2.1535%
5.20	1.0705%	28.4550%	26.2167%	2.2383%
5.30	1.0754%	29.0455%	26.7208%	2.3247%
5.40	1.0803%	29.6377%	27.2250%	2.4127%
5.50	1.0853%	30.2315%	27.7292%	2.5024%
5.60	1.0902%	30.8269%	28.2333%	2.5936%
5.70	1.0952%	31.4240%	28.7375%	2.6865%
5.80	1.1002%	32.0226%	29.2417%	2.7809%
5.90	1.1052%	32.6228%	29.7458%	2.8770%
6.00	1.1102%	33.2246%	30.2500%	2.9746%

贷款年限: 5年

利率	月供	等额本息利息	等额本金利息	利息差
3.00	1.7969%	7.8121%	7.6250%	0.1871%
3.10	1.8013%	8.0790%	7.8792%	0.1998%
3.20	1.8058%	8.3462%	8.1333%	0.2129%
3.30	1.8102%	8.6139%	8.3875%	0.2264%
3.40	1.8147%	8.8820%	8.6417%	0.2403%
3.50	1.8192%	9.1505%	8.8958%	0.2546%
3.60	1.8237%	9.4194%	9.1500%	0.2694%
3.70	1.8281%	9.6887%	9.4042%	0.2845%
3.80	1.8326%	9.9584%	9.6583%	0.3001%
3.90	1.8371%	10.2286%	9.9125%	0.3161%
4.00	1.8417%	10.4991%	10.1667%	0.3325%
4.10	1.8462%	10.7701%	10.4208%	0.3493%
4.20	1.8507%	11.0415%	10.6750%	0.3665%
4.30	1.8552%	11.3133%	10.9292%	0.3841%
4.40	1.8598%	11.5855%	11.1833%	0.4022%
4.50	1.8643%	11.8581%	11.4375%	0.4206%
4.60	1.8689%	12.1311%	11.6917%	0.4395%
4.70	1.8734%	12.4046%	11.9458%	0.4588%
4.80	1.8780%	12.6785%	12.2000%	0.4785%
4.90	1.8825%	12.9527%	12.4542%	0.4986%
5.00	1.8871%	13.2274%	12.7083%	0.5191%
5.10	1.8917%	13.5025%	12.9625%	0.5400%
5.20	1.8963%	13.7780%	13.2167%	0.5613%
5.30	1.9009%	14.0539%	13.4708%	0.5831%
5.40	1.9055%	14.3302%	13.7250%	0.6052%
5.50	1.9101%	14.6070%	13.9792%	0.6278%
5.60	1.9147%	14.8841%	14.2333%	0.6508%
5.70	1.9194%	15.1617%	14.4875%	0.6742%
5.80	1.9240%	15.4396%	14.7417%	0.6980%
5.90	1.9286%	15.7180%	14.9958%	0.7222%
6.00	1.9333%	15.9968%	15.2500%	0.7468%

贷款年限: 3年

利率	月供	等额本息利息	等额本金利息	利息差
3.00	2.9081%	4.6924%	4.6250%	0.0674%
3.10	2.9125%	4.8511%	4.7792%	0.0719%
3.20	2.9169%	5.0100%	4.9333%	0.0766%
3.30	2.9214%	5.1690%	5.0875%	0.0815%
3.40	2.9258%	5.3282%	5.2417%	0.0865%
3.50	2.9302%	5.4875%	5.3958%	0.0917%
3.60	2.9346%	5.6470%	5.5500%	0.0970%
3.70	2.9391%	5.8066%	5.7042%	0.1024%
3.80	2.9435%	5.9664%	5.8583%	0.1080%
3.90	2.9480%	6.1263%	6.0125%	0.1138%
4.00	2.9524%	6.2863%	6.1667%	0.1197%
4.10	2.9568%	6.4466%	6.3208%	0.1257%
4.20	2.9613%	6.6069%	6.4750%	0.1319%
4.30	2.9658%	6.7674%	6.6292%	0.1383%
4.40	2.9702%	6.9281%	6.7833%	0.1448%
4.50	2.9747%	7.0889%	6.9375%	0.1514%
4.60	2.9792%	7.2499%	7.0917%	0.1582%
4.70	2.9836%	7.4110%	7.2458%	0.1652%
4.80	2.9881%	7.5723%	7.4000%	0.1723%
4.90	2.9926%	7.7337%	7.5542%	0.1795%
5.00	2.9971%	7.8952%	7.7083%	0.1869%
5.10	3.0016%	8.0569%	7.8625%	0.1944%
5.20	3.0061%	8.2188%	8.0167%	0.2021%
5.30	3.0106%	8.3808%	8.1708%	0.2100%
5.40	3.0151%	8.5429%	8.3250%	0.2179%
5.50	3.0196%	8.7052%	8.4792%	0.2261%
5.60	3.0241%	8.8677%	8.6333%	0.2344%
5.70	3.0286%	9.0303%	8.7875%	0.2428%
5.80	3.0331%	9.1930%	8.9417%	0.2514%
5.90	3.0377%	9.3559%	9.0958%	0.2601%
6.00	3.0422%	9.5190%	9.2500%	0.2690%

贷款年限: 2年

利率	月供	等额本息利息	等额本金利息	利息差
3.00	4.2981%	3.1549%	3.1250%	0.0299%
3.10	4.3025%	3.2611%	3.2292%	0.0319%
3.20	4.3070%	3.3674%	3.3333%	0.0340%
3.30	4.3114%	3.4737%	3.4375%	0.0362%
3.40	4.3158%	3.5801%	3.5417%	0.0384%
3.50	4.3203%	3.6865%	3.6458%	0.0407%
3.60	4.3247%	3.7931%	3.7500%	0.0431%
3.70	4.3292%	3.8996%	3.8542%	0.0455%
3.80	4.3336%	4.0063%	3.9583%	0.0480%
3.90	4.3380%	4.1130%	4.0625%	0.0505%
4.00	4.3425%	4.2198%	4.1667%	0.0531%
4.10	4.3469%	4.3267%	4.2708%	0.0558%
4.20	4.3514%	4.4336%	4.3750%	0.0586%
4.30	4.3559%	4.5406%	4.4792%	0.0614%
4.40	4.3603%	4.6476%	4.5833%	0.0643%
4.50	4.3648%	4.7547%	4.6875%	0.0672%
4.60	4.3692%	4.8619%	4.7917%	0.0703%
4.70	4.3737%	4.9692%	4.8958%	0.0734%
4.80	4.3782%	5.0765%	5.0000%	0.0765%
4.90	4.3827%	5.1839%	5.1042%	0.0797%
5.00	4.3871%	5.2913%	5.2083%	0.0830%
5.10	4.3916%	5.3989%	5.3125%	0.0864%
5.20	4.3961%	5.5064%	5.4167%	0.0898%
5.30	4.4006%	5.6141%	5.5208%	0.0932%
5.40	4.4051%	5.7218%	5.6250%	0.0968%
5.50	4.4096%	5.8296%	5.7292%	0.1004%
5.60	4.4141%	5.9374%	5.8333%	0.1041%
5.70	4.4186%	6.0453%	5.9375%	0.1078%
5.80	4.4231%	6.1533%	6.0417%	0.1116%
5.90	4.4276%	6.2614%	6.1458%	0.1155%
6.00	4.4321%	6.3695%	6.2500%	0.1195%

贷款年限: 1年

利率	月供	等额本息利息	等额本金利息	利息差
3.00	8.4694%	1.6324%	1.6250%	0.0074%
3.10	8.4739%	1.6871%	1.6792%	0.0079%
3.20	8.4785%	1.7418%	1.7333%	0.0085%
3.30	8.4830%	1.7965%	1.7875%	0.0090%
3.40	8.4876%	1.8512%	1.8417%	0.0096%
3.50	8.4922%	1.9060%	1.8958%	0.0101%
3.60	8.4967%	1.9607%	1.9500%	0.0107%
3.70	8.5013%	2.0155%	2.0042%	0.0113%
3.80	8.5059%	2.0703%	2.0583%	0.0119%
3.90	8.5104%	2.1251%	2.1125%	0.0126%
4.00	8.5150%	2.1799%	2.1667%	0.0132%
4.10	8.5196%	2.2347%	2.2208%	0.0139%
4.20	8.5241%	2.2896%	2.2750%	0.0146%
4.30	8.5287%	2.3444%	2.3292%	0.0153%
4.40	8.5333%	2.3993%	2.3833%	0.0160%
4.50	8.5379%	2.4542%	2.4375%	0.0167%
4.60	8.5424%	2.5091%	2.4917%	0.0175%
4.70	8.5470%	2.5641%	2.5458%	0.0182%
4.80	8.5516%	2.6190%	2.6000%	0.0190%
4.90	8.5562%	2.6740%	2.6542%	0.0198%
5.00	8.5607%	2.7290%	2.7083%	0.0206%
5.10	8.5653%	2.7840%	2.7625%	0.0215%
5.20	8.5699%	2.8390%	2.8167%	0.0223%
5.30	8.5745%	2.8940%	2.8708%	0.0232%
5.40	8.5791%	2.9491%	2.9250%	0.0241%
5.50	8.5837%	3.0041%	2.9792%	0.0250%
5.60	8.5883%	3.0592%	3.0333%	0.0259%
5.70	8.5929%	3.1143%	3.0875%	0.0268%
5.80	8.5975%	3.1694%	3.1417%	0.0278%
5.90	8.6020%	3.2246%	3.1958%	0.0287%
6.00	8.6066%	3.2797%	3.2500%	0.0297%

loan_interest.py

#!/usr/bin/env python
#encoding:utf-8

import argparse, sys

def caculate_equal_payment_interest(rate, years):
    amount, total = 1.0, 0.0
    periods, period_rate = years * 12, rate / 100 / 12
    payment = amount * period_rate * pow(1 + period_rate, periods) / (pow(1 + period_rate, periods) - 1)
    while amount > 0:
        interest = amount * period_rate
        amount = amount - (payment - interest) 
        total += interest
    # print years, rate, total, payment
    return [total, payment]

def caculate_equal_principal_interest(rate, years):
    amount, total = 1.0, 0.0
    periods, period_rate = years * 12, rate / 100 / 12
    delta = amount / periods
    while amount > 0:
        interest = amount * period_rate
        amount -= delta
        total += interest
    # print years, rate, total
    return [total]

def caculate_interest(rate, years):
    principal = [x * 100 for x in caculate_equal_principal_interest(rate, years)]
    payment = [x * 100 for x in caculate_equal_payment_interest(rate, years)]
    print '|%.2f|%.4f%%|%8.4f%%|%8.4f%%|%7.4f%%|'%(rate, payment[1],payment[0],principal[0],payment[0] - principal[0])

def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('-y', '--years', default = [30], nargs = '+', help = 'number of loan years')
    parser.add_argument('-r', '--interest-rate', required = True, help = 'bank loan interest rate')
    parser.add_argument('-g', '--interest-rate-range', default = 1.5, help = 'interest rate range list')
    data = parser.parse_args(sys.argv[1:])
    years_list = [int(x) for x in data.years]
    for case_years in years_list:
        print '## 贷款年限: %r年'%(case_years)
        interest_rate = float(data.interest_rate)
        interest_rate_upper = interest_rate + float(data.interest_rate_range)
        print '|利率|月供|等额本息利息|等额本金利息|利息差|'
        table_format = '|'
        for n in range(5):
            table_format += ':-:|'
        print table_format
        while interest_rate < interest_rate_upper:
            caculate_interest(interest_rate, case_years)
            interest_rate += 0.1
        print

if __name__ == '__main__':
    main()