A python function to compute NFL passer rating.

passer_rating.py

def handle_nfl_passer_rating(cmpls, yds, tds, ints):
     """ Defines a function which handles passer rating calculation for the NFL."""
     def _min_max(x, xmin, xmax):
         """
         Defines a function which enforces a minimum and maximum value.
         Input: x, the value to check.
         Input: xmin, the minumum value.
         Input: xmax, the maximum value.
         Output: Either x, xmin or xmax, depending.
         """
         # Check if x is less than the minimum. If so, return the minimum.
         if x < xmin:
             return xmin
         
         # Check if x is greater than the maximum. If so, return the maximum.
         elif x > xmax:
             return xmax
         
         # Otherwise, just return x. And weep for the future.
         else:
             return x
             
     # Step 0: Make sure these are floats, dammit.
     cmpls = cmpls + 0.0
     yds = yds + 0.0
     tds = tds + 0.0
     ints = ints + 0.0
     
     # Step 1: The completion percentage.         
     step_1 = cmpls - 0.3
     step_1 = step_1 * 5
     step_1 = _min_max(step_1, 0, 2.375)
     
     # Step 2: The yards per attempt.
     step_2 = yds - 3
     step_2 = step_2 * 0.25
     step_2 = _min_max(step_2, 0, 2.375)
     
     # Step 3: Touchdown percentage.
     step_3 = tds * 20
     step_3 = _min_max(step_3, 0, 2.375)
     
     # Step 4: Interception percentage.
     step_4 = ints * 25
     step_4 = 2.375 - step_4
     step_4 = _min_max(step_4, 0, 2.375)
     
     # Step 5: Compute the rating based on the sum of steps 1-4.
     rating = step_1 + step_2 + step_3 + step_4 + 0.0
     rating = rating / 6
     rating = rating * 100
     
     # Step 6: Return the rating, formatted to 1 decimal place, as a Decimal.
     return rating

Ported it to Objective-C: https://gist.github.com/2216724