Floating Point Python

Question

How this loop is performing and why it doesn't print 2.399999999999999

i = 1.2

while i < 2.4:
    print(i)
    i += 0.2

Also when I tried :

2.39999999999999999 < 2.4

I got False

But when I tried :

2.399999999999999 < 2.4

I got True

Can anyone explain why it is so ?

Do you understanding floating point imprecision? What are you trying to do? — Chris_Rands, Jul 02 '21 at 15:54
Hi @Chris_Rands Can you spread some light or refer me any documentation for the same, I am still not clear why 2.39999999999999999 < 2.4 is False and 2.399999999999999 < 2.4 is True. — Deepak Tripathi, Jul 02 '21 at 15:56
Your first example `2.39999999999999999 < 2.4` is equivalent to `2.4 < 2.4` because of the limited precision of floating point. — Mark Ransom, Jul 02 '21 at 15:56
See [Is floating point math broken?](https://stackoverflow.com/q/588004/5987) — Mark Ransom, Jul 02 '21 at 15:58
To see what I'm talking about, try `2.39999999999999999 == 2.4`. — Mark Ransom, Jul 02 '21 at 16:00

score 1 · Answer 1 · answered Jul 02 '21 at 15:54

1

This is because computer architecture either rounds the number or truncate the number. In this scenario, if we see architecture level either considering the number equals to 2.4 or greater than just by Machine epsilon.

It is good to have a look at the concept of Machine Epsilon.

answered Jul 02 '21 at 15:54

bugger

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So 2.39999999999999999 < 2.4 is False and 2.399999999999999 < 2.4 is True due to Machine Epsilon ? – Deepak Tripathi Jul 02 '21 at 15:56
@DeepakTripathi it's because the difference between 2.39999999999999999 and 2.4 is less than half of epsilon*2.4. – Mark Ransom Jul 02 '21 at 21:47

Floating Point Python

1 Answers1