Round problem

Question

print(round(4.5))
print(round(3.5))
print(round(2.5))
print(round(1.5))
print(round(0.5))
print(round(-.05))
print(round(-1.5))
print(round(-2.5))
print(round(-3.5))
print(round(-4.5))

>>>
4
4
2
2
0
0
-2
-2
-4
-4

Why???
Why not 5 4 3 2 1 0 -1 -2 -3 -4 ?

Answer 1

It's normal, python3 and some other langs like c# use "banker's rounding" (rounding to nearest even number) instead of normal math rounding.
But python2 use normal math rounding.