comparing floats

Question

Hi all

Why does print(5.9>5.12) print true? I know comparing the floats is problematic.

I just uploaded a very simple database like object to github for use in godot. If anyone is interested it is at https://github.com/sxkod/dbx .

However I am struggling with making the comparisons work reliably when dealing with floats.

Any help appreciated.

Answer 1

This is correct: 5.9 is a bigger number than 5.12.

Floats are problematic if you are comparing for equality, due to rounding errors inherent in the binary representation of floating point numbers. Greater/less than comparisons are generally fine.

Comments

oh ok. Thought I was losing my mind!
You are correct - < and > work fine. It is the equality that causes problems.
Is there a way around it then ?

Thanks and have a good weekend.

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If you need to compare the equality of two floating point numbers, you can do so with some epsilon value, a small amount representing the precision you need. The numbers are effectively equal if they're within that tiny amount:

if abs(a - b) < 0.000001:
    print("a equals b")

Another way of handling it is to round the two numbers to a reasonable number of digits, ie 1.0 instead of 1.0000000003

See Wikipedia for more information on floating point arithmetic.

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Got it. I decided to go with testing if the field is a real number and then use formatting to 4 points. Thanks for your help.