CODEWITHSUNDEEP
python-3.x
InstantNut
InstantNut

Reputation: 93

How to add percentage sign to eval() result?

So I am trying to insert a percentage sign at the end of my output for the variable rate. However I am getting a "TypeError: unsupported operand type(s) for +: 'float' and 'str'" error." How do I format the output so that I could put a '%' sign on it.

Loan = eval(input("Enter loan amount, for example 120000: "))

while Loan <= 12000 or Loan >= 125000:
    print("Please enter a value more than 120000 or less than 125000")
    Loan = eval(input("Enter loan amount, for example 120000: "))
Year = eval(input("Enter number of years as an integer, for example 7: "))

while Year < 5 or Year >10:
    print("Please enter a number more than 5 or less than 10")
    Year = eval(input("Enter number of years as an integer, for example 7: "))

print('%-20s%-20s%-20s' % ('Interest Rate', 'Monthly Payment', 'Total Payment'))

Rate = 5.0
while Rate <= 8:
    adjRate = Rate / 1200
    monthlyPayment = Loan * adjRate / (1 - 1 / (1 + adjRate) ** (Year * 12))
    totalPayment = monthlyPayment * Year * 12
    print('%-20.3f%-20.2f%-20.2f' % (Rate, monthlyPayment, totalPayment))
    Rate += 0.125

I tried: print('%-20.3f%-20.2f%-20.2f' % (Rate+'%', monthlyPayment, totalPayment))

but got an 

TypeError: unsupported operand type(s) for +: 'float' and 'str'"

Upvotes: 0

Views: 741

Answers (3)

user11093202
user11093202

Reputation:

Just use print("what ever you want here", end = "%")

Upvotes: 0

Ray Toal
Ray Toal

Reputation: 88478

Since Rate is a float and '%' is a str, the expression

Rate + '%'

is indeed illegal: in Python, you cannot "add" a float and a str.

So that's the cause of the specific error you inquired about. To fix it, you can do the following:

print('%20.3f%s%20.2f%20.2f' % (Rate, '%', monthlyPayment, totalPayment))

So that the %s in the format string gets you the %.

I also removed the negative signs, as numbers should generally be right aligned.

If you are using Python 3.6 or above I highly recommend writing this as:

print(f'{Rate:20.3f}%{monthlyPayment:20.2f}{totalPayment:20.2f'})

Again, this just answers the reason for your error. The use of eval is actually another matter; it should not be used the way you used it here. (Just pointing that out since I feel an obligation to do so.)

Upvotes: 2

dwagon
dwagon

Reputation: 511

Never use eval on user input, use input and validate what is entered; otherwise this opens up so many security holes.

Instead use conversion commands like float() and int().

So, for example:

loan_str = input("Enter loan amount")
loan_amt = int(loan_amt)

Wrap everything in try/except to catch people putting in "fifty thousand" instead of "50000"

This will also ensure that your values are the correct type for your code.

To embed a '%' in your string use '%%'

Upvotes: 2

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