如何更改python for循環中的變量？

我想在python中製作一個計算信用卡上剩餘餘額的程序。它用於MIT開放課件"Introduction to Computer Science and Programming"。我在做problem set one。如何更改python for循環中的變量？

程序必須要求用戶啓動變量：起始餘額，年利率和最低月度支付。這是我的代碼。

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))

如何獲得剩餘餘額以正確更新？我無法弄清楚如何在每個月底更新餘額。到目前爲止，每個月的最低月還款額，本金支付和剩餘餘額都會返回相同的值。

來源

2013-10-16 Robert Westenberger

您在整個循環中使用相同的initialOutstandingBalance變量，並且永遠不會更改它。相反，您應該跟蹤當前的餘額。這將等於循環開始時的初始未結餘額，但會在運行時發生變化。

你也不需要一直打電話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))

來源

2013-10-16 22:05:31

你要保持變量newBalance外循環，否則它會被重新分配每個迭代。此外，您不希望將利率除以餘額的12倍，而是將其除以12，然後將商數乘以餘額。最後，如上所述，您不需要所有的float。

這應該工作：

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))

來源

2013-10-16 22:20:18 Impossibility

如何更改python for循環中的變量？

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