贷款支付计算

Question

我正在学习 Python 并且卡住了。我正在尝试查找贷款支付金额。我目前有：

def myMonthlyPayment(Principal, annual_r, n):
    years = n
    r = ( annual_r / 100 ) / 12
    MonthlyPayment = (Principal * (r * ( 1 + r ) ** years / (( 1 + r ) ** (years - 1))))
    return MonthlyPayment

n=(input('Please enter number of years of loan'))
annual_r=(input('Please enter the interest rate'))
Principal=(input('Please enter the amount of loan'))

但是，当我跑步时，我跑了一点点。如果有人能指出我的错误，那就太好了。我正在使用 Python 3.4。

Answer 1

付款计算方面，您似乎没有正确翻译formula。除此之外，由于内置的​​input() 函数返回字符串，因此在将值传递给期望它们为数值的函数之前，您需要将它返回的任何内容转换为正确的类型。

def myMonthlyPayment(Principal, annual_r, years):
    n = years * 12  # number of monthly payments
    r = (annual_r / 100) / 12  # decimal monthly interest rate from APR
    MonthlyPayment = (r * Principal * ((1+r) ** n)) / (((1+r) ** n) - 1)
    return MonthlyPayment

years = int(input('Please enter number of years of loan: '))
annual_r = float(input('Please enter the annual interest rate: '))
Principal = int(input('Please enter the amount of loan: '))

print('Monthly payment: {}'.format(myMonthlyPayment(Principal, annual_r, years)))

Answer 2

我认为在你计算的最后一点，

/ (( 1 + r ) ** (years - 1))

你的括号错误；应该是

/ ((( 1 + r ) ** years) - 1)

Answer 3

我认为正确的公式是这样的，

MonthlyPayment = (Principal * r) / (1 - (1 + r) ** (12 * years))

我清理了你的一些变量，

def get_monthly_payment(principal, annual_rate, years):
    monthly_rate = annual_rate / 100 / 12
    monthly_payment = principal * (monthly_rate + monthly_rate / ((1 + monthly_rate) ** (12 * years) - 1))
    return monthly_payment

years = float((input('Please enter number of years of loan')))
annual_rate = float((input('Please enter the interest rate')))
principal = float((input('Please enter the amount of loan')))
print ("Monthly Payment: " + str(get_monthly_payment(principal, annual_rate, years)))

在输入周围添加一个 try-except 块也是谨慎的做法。