module python shows a wrong answer (floats module)

Question

couldn't fine answer here. my code:

t = 0
i = 0
arrival = 7.2
while t < 3600:
    time_passed = 0.1
    if t % arrival == 0:
         i+=1
    t+= time_passed
print (i)

===> I get 1 for some reason. can't understand how to fix it (it should be 500) edit: I want to know how to change my code in order to fix the issue, not the theory behind..

Possible duplicate of [Is floating point math broken?](https://stackoverflow.com/questions/588004/is-floating-point-math-broken) — DeepSpace, Dec 29 '18 at 19:12

score 2 · Accepted Answer · answered Dec 29 '18 at 19:23

Its because of floating point rounding issues. You can read this post on why it happens.

If you want a quick fix, just use pythons decimal library.

from decimal import Decimal
t = 0
i = 0
arrival = Decimal('7.2')
while t < 3600:
    time_passed = Decimal('0.1')
    if t % arrival == 0:
         i+=1
    t+= time_passed
print (i)

module python shows a wrong answer (floats module)

1 Answers1