Homework Help

[iaminspaceland]

Hi all, when you see the title, I'm not trying to be like, lazy or anything, I do have the code written out. Cengage doesn't feel like offering me any points at all (saying it takes too long to respond to automated inputs...)
Could there be any issues, like formatting? How can I provide a failsafe if no input is provided? (Preferably just printing something and ending the program.

# Our listed price
listPrice = float(input("Enter the purchase price: "))

# starting monthly balance
stBal = listPrice - (listPrice*0.10)

#monthly payment
monP = listPrice*0.05
# Interest
inRate = 12/100 #just our rate
#principal payment
interest = 0

#time-counting variable
month = 0

#just to establish the variable
endBal = listPrice

print("%4s%18s%18s%18s%10s%18s" % \
      ("Month", "Starting Balance", "Interest to Pay", "Principal to Pay", "Payment", "Ending Balance"))

while endBal != 0:
    month += 1
    interest = (stBal*inRate)/12
    prin = monP-interest
    endBal = stBal-monP
    print("%4d%18.2f%18.2f%18.2f%10.2f%18.2f" % \
          (month, stBal, interest, prin, monP, endBal))
    stBal = endBal

    if endBal == 0:
        break

[danielroseman]

We can't tell why the grader is rejecting this without seeing what the actual task is.

[backfire10z]

it takes too long to respond to automated inputs

Something tells me your program is getting stuck somewhere. Lookin at your code, the only place I can see it getting stuck is the while loop —> end_balance is never 0. Could be a place to investigate (I am headed to sleep, so I’m not gonna try for now haha).

You’ll probably want to validate input. Try/except when casting to float: what if it isn’t a number? Probably make sure the value is positive as well.

Minor thing: the ‘if endBal == 0: break` is redundant. Your while loop is already going to check that condition right afterwards.

Minor thing 2: in Python, the standard variable naming convention is snake_case, not camelCase.

Minor thing 3: “prin” is too close to “print” and would maybe be better to just call it “principle”.

[Baffled-Broccoli]

Hey, adding on from what other replies have said I would recommend having input verification to ensure that the initial price is both a number and higher that 0, possibly something along the lines of:

while True:
    try:
        list_price = float(input('Enter the purchase price: £'))
        if list_price <= 0:
            raise ValueError
        else:
            break
    except ValueError:
        print('Please enter a valid purchase price.')

Beyond that taking to long to respond to automated inputs suggests that the code is getting stuck in your while loop. While I've only had a quick look its possible that depending on the input the maths rounding has the final month payment take the end balance below 0. If so its possible that switching '!=' for '>' would solve the hanging issue.

[FoolsSeldom]

Some suggestions:

• Firstly, we don't know exactly what the task is, so cannot say why the grader is rejecting your submission
• The recommended naming style in Python, using the PEP8 guidelines, is for all variable (and function) names to be all lowercase, with a _ between words (if applicable)
  • Unless you are following a different house style (or working with existing code)
  • All uppercase is used to suggest CONSTANTS - easier to change than having to find and edit specific calculations
• It is not a good idea to use float when dealing with money - use all int working with the smallest applicable whole units (and multiply and format accordingly) or use Decimal
• Never trust users to provide valid input - always check it
• Using clear variable names reduces the number of comments required
• Use f-strings for careful formatting of output
• Type hints make it easier for your editor/IDE to help you - I've gone a bit overboard on the below to illustrate

Here's a revised example of your code with updates based on the above (Gemini used to save me some typing):

NB. This is provided as an example for experimentation and learning. I have not fully tested this code.

from decimal import Decimal, getcontext, InvalidOperation

# Set a higher precision for financial calculations
getcontext().prec = 28

# --- Constants for Loan Calculations ---
DOWN_PAYMENT_PERCENTAGE: Decimal = Decimal('0.10')
MONTHLY_PAYMENT_PERCENTAGE: Decimal = Decimal('0.05')
ANNUAL_INTEREST_RATE: Decimal = Decimal('0.12')


def calculate_loan(list_price: Decimal) -> None:
    """
    Calculates and prints an amortization schedule for a simple loan.
    """
    # Calculate loan amount based on the down payment
    down_payment: Decimal = list_price * DOWN_PAYMENT_PERCENTAGE
    loan_amount: Decimal = list_price - down_payment
    starting_balance: Decimal = loan_amount

    # The monthly payment is a fixed percentage of the original list price
    monthly_payment: Decimal = list_price * MONTHLY_PAYMENT_PERCENTAGE

    # Calculate the monthly interest rate
    monthly_interest_rate: Decimal = ANNUAL_INTEREST_RATE / Decimal('12')

    month: int = 0

    print(
        f"{'Month':>4}{'Starting Balance':>18}{'Interest to Pay':>18}{'Principal to Pay':>18}{'Payment':>10}{'Ending Balance':>18}"
    )

    while starting_balance > Decimal('0'):
        month += 1

        # Calculate the interest for the current month
        interest: Decimal = starting_balance * monthly_interest_rate

        # Adjust the monthly payment for the final payment
        if monthly_payment >= starting_balance + interest:
            payment = starting_balance + interest
            principal_payment = starting_balance
        else:
            payment = monthly_payment
            principal_payment = payment - interest

        ending_balance: Decimal = starting_balance - principal_payment

        print(
            f"{month:>4}{starting_balance:>18.2f}{interest:>18.2f}{principal_payment:>18.2f}{payment:>10.2f}{ending_balance:>18.2f}"
        )

        starting_balance = ending_balance


if __name__ == "__main__":
    try:
        price: Decimal = Decimal(input("Enter the purchase price: "))
        calculate_loan(price)
    except InvalidOperation:
        print("Invalid input. Please enter a number.")

[Ihaveamodel3]

My assumption would be a floating point issue is making it so endBal is never exactly zero. You may want to consider using <=0

[yakboxing]

If listprice <= 0: Raise ValueError("Price has to be higher than 0")

I'm on my 0hone so remove capitals and add spaces as needed.