Question

我正在尝试在python中创建一个计算信用卡剩余余额的程序。这是麻省理工学院开放课件"Introduction to Computer Science and Programming"。我正在做problem set one。

程序必须询问用户启动变量：起始余额，年利率和最低月付款。这是我的代码。

initialOutstandingBalance= float(raw_input('What is the outstanding balance on your  
card?'))
annualInterestRate=float(raw_input('What is the annual interest rate expressed as a   
decimal?'))
minimumMonthlyPaymentRate=float(raw_input('What is the minimum monthly payment rate on
your card expressed as a decimal?'))

for month in range(1,13):
    print("Month: "+ str(month))
    minimumMonthlyPayment=float(minimumMonthlyPaymentRate*initialOutstandingBalance)
    interestPaid=float((annualInterestRate)/(12*initialOutstandingBalance))
    principalPaid=float(minimumMonthlyPayment-interestPaid)
    newBalance=float(initialOutstandingBalance-principalPaid)
    print("Minimum monthly payment: $"+str(minimumMonthlyPayment))
    print("Principle paid: $"+str(principalPaid))
    print("Remaining Balance: $"+str(newBalance))

如何让剩余余额正确更新？我无法弄清楚如何在每个月末更新余额。到目前为止，每个月都会返回最低月付款，已付本金和余额的相同值。

Answer 1

您在整个循环中使用相同的initialOutstandingBalance变量，并且从不更改它。相反，您应该跟踪当前的余额。这将等于循环开始时的初始未结余额，但会在运行时发生变化。

您也无需继续致电float。

current_balance = initialOutstandingBalance
for month in range(1,13):
    print("Month: "+ str(month))
    minimumMonthlyPayment = minimumMonthlyPaymentRate * current_balance
    # this calculation is almost certainly wrong, but is preserved from your starting code
    interestPaid = annualInterestRate / (12*current_balance)
    principalPaid = minimumMonthlyPayment - interestPaid
    current_balance = current_balance - principalPaid
    print("Minimum monthly payment: $"+str(minimumMonthlyPayment))
    print("Principle paid: $"+str(principalPaid))
    print("Remaining Balance: $"+str(current_balance))

Answer 2

您希望将变量newBalance保留在循环之外，否则每次迭代都会重新分配。此外，您不希望将利率除以余额的12倍，而是将其除以12，然后将商乘以余额。最后，如上所述，您不需要所有float个。

这应该有效：

newBalance = initialOutstandingBalance

for month in range(1,13):
    print("Month: " + str(month))

    minimumMonthlyPayment = minimumMonthlyPaymentRate * newBalance
    interestPaid = annualInterestRate / 12 * newBalance
    principalPaid = minimumMonthlyPayment - interestPaid
    newBalance -= principalPaid

    print("Minimum monthly payment: $" + str(minimumMonthlyPayment))
    print("Principle paid: $" +  str(principalPaid))
    print("Remaining Balance: $" + str(newBalance))

如何在python中更改for循环中的变量？

2 个答案: