[Tutor] function return values

[Phil]

I was quite pleased with myself that I had reduced the complexity of a 
function until I tried to reuse the same code elsewhere. I had the 
return values set to some dummy values and that was good in this case. 
However, this idea failed when I tried to test if the pairs are in the 
same column. So, what is the correct way to handle a case where there 
isn't a valid pair, row or list value to return?

     def boxPairsInSameRow(self, pairs, x, y):
         col_list = []

         for item, count in pairs.items():
             if count == 2:  # then item is a pair candidate
                 for row in range(x, x + 3):
                     col_list = []
                     for col in range(y, y + 3):
                         if item in self.solution[row][col]:
                             col_list.append(col)
                     return item, row, col_list
         return None, None, None # item, row and col_list were 
originally dummy values

This is the calling function:

             item, row, column_list = 
self.boxPairsInSameRow(candidate_pairs, x , y)
             if item is not None and row is not None and column_list is 
not None:
                 do this only if the returned values are valid. In other 
words, this is a pair in a row.

Maybe the boxPairsInSameRow function is still too complex? The aim is to 
feed in the pairs, from a counter dictionary, and the row and column 
starting coordinates and have it return the pairs.item, the row that the 
item is on and a list containing the two columns for that row position. 
Once the pairs have been found on a row then there is no need to search 
the remaining row or rows.

It all sounds simple, however, evidently it's not simple enough.

-- 
Regards,
Phil