Python 类型错误 : unsupported operand type(s) for -: 'int' and 'function'

Question

我是 Python 初学者，正在做一项作业。即使在研究错误并应用建议的修复之后，我仍然收到 TypeError: unsupported operand type(s) for -: 'int' and 'function' 。我并不是在寻找任何人给我一个解决方案，但我会很感激再看一眼。我错过了一些东西，但我不知道是什么。这是我遇到问题的代码部分:

month = 0
interestYDT = 0
balance = int(raw_input ("Enter balance on credit card: "))
annualInterestRate = float(raw_input ("Enter annual interest rate as a decimal: "))
monthlyPaymentRate = float(raw_input ("Enter minimum monthly payment rate as a decimal: "))
previousbalance = balance
#
def monthlyInterestRate(annualInterestRate):
    return float(annualInterestRate/12)
#
if month <= 12:
    def minimumMonthlyPayment(previousbalance):
        return (previousbalance * monthlyPaymentRate)
    def monthlyInterest(monthlyInterestRate):
        return (1 + monthlyInterestRate)
    minMonPay = minimumMonthlyPayment
    monInt = monthlyInterest
    newbalance = ((previousbalance - minMonPay) * (monInt))
    interestYDT = (interestYTD + montInt)
    previousbalance = (newbalance)
    print ''
    print ('Month:' (month))
    print ('Minimum monthly payment: $ ' (round(minimumMonthlyPayment, 2)))
    print ('Remainging balance: $ ' (round(newbalance, 2)))
    print ' '
    month = (month + 1)

这是我得到的整个错误:

Traceback (most recent call last):
  File "C:/Users/Karla/Documents/_MIT 600X Introduction to CS and Prog/Assignments/Week2/kmarciszewski_week2_Problemset_Problem1.py", line 33, in <module>
    newbalance = ((previousbalance - minMonPay) * (monInt))
TypeError: unsupported operand type(s) for -: 'int' and 'function'

我真的很感激任何见解。谢谢。

Answer 1

为了调用函数，您必须在函数名称以及任何必需的参数后面添加括号。

在这两行中

minMonPay = minimumMonthlyPayment
monInt = monthlyInterest

您将函数分配给名称 minMonPay、monInt，但实际上并未调用它们。相反，您需要编写如下内容:

minMonPay = minimumMonthlyPayment(previousBalance)
monInt = monthlyInterest(monthlyInterestRate)

这个定义

def minimumMonthlyPayment(previousbalance):
    return (previousbalance * monthlyPaymentRate)

为您提供一个函数，该函数采用一个参数并将其称为 previousBalance。它与您之前在代码中创建的变量无关。事实上，我建议你重命名它，它只会让你作为初学者感到困惑。

此外，您创建的函数非常简单，每个函数仅使用一次，因此删除它们并内联代码可能符合您的利益。

# OLD CODE
def minimumMonthlyPayment(previousbalance):
    return (previousbalance * monthlyPaymentRate)
def monthlyInterest(monthlyInterestRate):
    return (1 + monthlyInterestRate)
minMonPay = minimumMonthlyPayment
monInt = monthlyInterest

# NEW CODE
minMonPay = previousbalance * monthlyPaymentRate
monInt = 1 + monthlyInterestRate

如果执行此操作，请不要忘记更新错误使用minimumMonthlyPayment 函数的行。

# OLD CODE
print ('Minimum monthly payment: $ ' (round(minimumMonthlyPayment, 2)))

# NEW CODE
print ('Minimum monthly payment: $ ' (round(minMonPay, 2)))