# Magic
## mapping to +1,-1,0

sign = (x > 0) - (x < 0)

## mapping to +1 (x>=0), -1

sign = [1, -1][x < 0] 
# a = [1, -1] 
# flag = x < 0 
# a[flag]

## digit reversion

int(str(s)[::-1])  # on the base on ten