python code

self.hours = 1 + (self.hours - 1) % 12

Obviously written by a moran.  It evaluates to:

self.hours = self.hours % 12

Which sets self.hours to a value from 0..11 depending on the remainder after dividing it by 12.  I can't see any surrounding code, but I guess it could be used when you have a number of hours representing 24-hour time and you just wanted to know which hour /12 that would be when using AM/PM instead of 24-hour time.