Question

Question about assignment 1 part 3
I've come up with the following:

balance= float(input('initial balance:'))
interestrate= float(input('annual interest rate:'))

low= balance/12
high= balance*(1+interestrate)/12
payment= (high + low)/2.0
numMonths = 0

while payment*12 - balance != 0:
if payment*12 < balance:
low = payment
else:
high = payment

Answer 1

while numMonths <= 12 and balance > 0:

interest = balance*interestrate/12
principlerepayment = (payment - balance*interestrate/12)
balance -= principlerepayment
numMonths += 1

print ("Month:", numMonths)
print ('Interest payment:', interest)
print ('Remaining balance:', balance)
print ('payment', payment)

The trouble seems to be I overshoot the number of months slightly and don't get a round answer. Any help understanding why this happens would be appreciated.

Answer 2

You should not do equals comparisons with floats or doubles. You should always be doing >, <, >=, <= comparisons.

Answer 3

I see your point and that's probably good practice generally. But I did use a more complex statement earlier with such conditions and it doesn't seem to make a difference to the problem I'm having.