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Thread: APR Interest Calculator help

02062012, 04:11 AM #1
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APR Interest Calculator help
I'm taking an introductory course to python and I'm having really frustrating time as this is very simple and i have done programming much more complex and just getting really frustrated on being hung up on this.
So my assignment is to create a calculator that does APR interest using the formula
Where A is the monthly payment, P is the total amount borrowed (the principal), n is the number of months for repayment and i is the monthly interest rate. You can calculate the monthly interest rate by dividing the annual interest rate ("APR") by 12.
For example, to borrow $30,000 (P) for a 10 year term (n = 120) with an APR interest rate of 6% (i = 0.06 / 12 = 0.005), A calculates to be $333.06  the monthly payment. The total interest paid over 10 years (always depressing!) = 120 * $333.06  $30,000 = $9,967.38.
Code:def main(): print("****************************************") print("Mortgage Calculator v1.0") print("****************************************") print("") principal = float(input("Principal Amount ")) years = int(input("Input number of years ")) interest = float(input("Input interest percentage ")) interest = (interest/100)/12 months = years*12 monthly_payments = principal*interest/1(1+interest)**months print(apr) print("After", Years, "years at", format(interest, '.0%'), " interest ", "total is", format(Total, '.2f')) print("Monthly payments will be", monthly_payments) print("Total interest will amount to", format(total_interest, '.2f')) main()

03112012, 11:29 PM #2
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So just as a starting point it may be helpful to have another function to handle calculations and a function to handle input and call the calculating function.
Not sure which variables you'd want to have but here:
Code:def apr(principal, years, interest): top = principal*interest; bottom = 1  (1+interest)**(1*years); return round(top/bottom, 2); def main(): print apr(1000, 1, 0.06); print apr(1000, 2, 0.06); print apr(1000, 3, 0.06); main();
If you want to test you can type 'python' import your code (if the filename is 'apr' then 'import apr' and test like so 'apr.apr(principal, years, interest)';
That should help you test faster.
Now you handle the input. Make sure you convert to int() or float() where appropriate.Last edited by fatecaresx13; 03112012 at 11:33 PM.