Why 1-0.9 is not 0.1?

Question

Why when I'm doing this simple math subtraction I get this answer ?

In[10]: 1-0.9
Out[10]: 0.09999999999999998

someone know how to fix this ?

score 3 · Accepted Answer · answered Dec 25 '15 at 06:37

3

Use round(1-0.9, n) where it rounds the result to n decimal places

answered Dec 25 '15 at 06:37

Amal Ts

Thank you for your answer and the reference, this is very helpful. – limitless Dec 25 '15 at 06:52
This is only a fix because this operation reduces the number of bits in the significand. In operations where the size of the significand does not change this will have no effect. – Ignacio Vazquez-Abrams Dec 25 '15 at 07:16

score 0 · Answer 2 · answered Dec 25 '15 at 06:36

0

This is a common problem with floating point precision. Usually people round when floats are displayed so the precision limitation is not shown.

answered Dec 25 '15 at 06:36

David Maust

2 Answers2