## sidonsoft 2 years ago my code is off by 10 compared to other test cases, but not all the time, any ideas? balance = 4157 annualInterestRate = 0.18 payment = 10 def payforyear(x): count = 0 while count < 12: x = (x - payment) + (x*(annualInterestRate / 12)) count = count + 1 if count == 12: return x while payforyear(balance) > 0: payment = payment + 10 else: print ('Lowest payment: ' +str(payment) )

1. Chris2332

Why do you check if count == 12? Since the while loop will end anyway when the count reaches 12, you can just return the value!

2. sidonsoft

if i recall correctly, if i didn't check count 12 and put the return x line in it returned the result after one iteration of the loop

3. msmithhnova

Well, the main thing that is wrong is the formula (x-paymnet)+(x*(annualInterestRate/12)) If you check instructions it is (xipayment)*(1-(annualInterestRate/12)) This will fix your problem but stylistically using variables defined outside the function is bad practice unless absolutely necessary.

4. Chris2332

Sorry just to be clear, which exercise are you trying to solve? I guess it's the second one!

5. msmithhnova

6. msmithhnova

And (1+(... not minus

7. Chris2332

x = (x - payment) *(1+annualInterestRate / 12) should do the trick I guess

8. sidonsoft

Yes, it does actually problem is I have no idea how, and why i got it wrong in the first place. I have looked at that area of the code more than a few times over the past 12 hours I have been working on it. I have this weird feeling that my solution is very very very far from other peoples solutions.

9. msmithhnova

Yes and as chris said previously the if count==12 is not necessary as long as the return statement is lined up with the while, I tested it too.

10. sidonsoft

yes thank you for that Chris, I am still getting my head around logic and python work flow. I was scratching my head with the while statement and indentation for a good couple of hours.

11. msmithhnova

Indentation in python is very important to the meaning and this is a good reason for beginners to learn python because it forces good habits of indentation. Which isn't necessary in some languages but always recommended.

12. Chris2332

Ditto!