3 Operator Module Functions The key-function patterns shown above are very common, so Python provides convenience functions to make accessor functions easier and faster. The operator module has itemgetter() , attrgetter() , and a methodcaller() function. Using those functions, the above examples become simpler and faster: >>> from operator import itemgetter, attrgetter The operator module functions allow multiple levels of sorting. For example, to sort by grade then by age : Both$_{list.sort()}$ and$_{sorted()}$ accept a reverse parameter with a boolean value. This is used to flag descend- ing sorts. For example, to get the student data in reverse age order: Sorts are guaranteed to be stable. That means that when multiple records have the same key, their original order is preserved. Notice how the two records for blue retain their original order so that$_{('blue', 1)}$ is guaranteed to precede ('blue', 2) . This wonderful property lets you build complex sorts in a series of sorting steps. For example, to sort the student data by descending grade and then ascending age , do the age sort first and then sort again using grade : 3 >>> s =sorted(student_objects, key =attrgetter( 'age')) # sort on secondary key >>> sorted(s, key =attrgetter( 'grade'), reverse = True ) # now sort on primary ␣ ↪ → key, descending [('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)] >>> data =[('red',1), ( 'blue',1), ( 'red',2), ( 'blue',2)] >>> sorted(data, key =itemgetter(0)) [('blue', 1), ('blue', 2), ('red', 1), ('red', 2)] 5 Sort Stability and Complex Sorts 4 Ascending and Descending >>> sorted(student_tuples, key =itemgetter(2)) [('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)] >>> sorted(student_objects, key =attrgetter( 'age')) [('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)] >>> sorted(student_tuples, key =itemgetter(1,2)) [('john', 'A', 15), ('dave', 'B', 10), ('jane', 'B', 12)] >>> sorted(student_objects, key =attrgetter( 'grade','age')) [('john', 'A', 15), ('dave', 'B', 10), ('jane', 'B', 12)] >>> sorted(student_tuples, key =itemgetter(2), reverse = True ) [('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)] >>> sorted(student_objects, key =attrgetter( 'age'), reverse = True ) [('john', 'A', 15), ('jane', 'B', 12), ('dave', 'B', 10)]