Why Is Rounding 0.5 (decimal) Not Exact?

One half, i.e. 0.5 in decimal, has an exact binary representation: 0.1 Nevertheless, if I round it to integer, I get 0 instead of 1. I tried in Python and C, which behave the same.

Solution 1:

I know they changed the round method in python 3.

So, under v2.7.3:

In[85]: round(2.5)
Out[85]: 3.0In[86]: round(3.5)
Out[86]: 4.0

under v3.2.3:

In[32]: round(2.5)
Out[32]: 2In[33]: round(3.5)
Out[33]: 4

I don't know if it helps you but I am posting it as answer since I can't comment due to my low reputation.

The question is answered more properly here : Python 3.x rounding behavior