# As usually just making some data for an experiment pairs = [(1, 'one'), (2, 'two'), (3, 'three'), (4, 'four')] # And here... We're define small single-expression function on fly to operate # with values of list and chose which one would be used to sort list. pairs.sort(key=lambda pair: pair[1]) print(pairs) print # It actually would be pretty equal to following way of doing the same. # Redefine initial data, cause our list is already sorted. pairs = [(1, 'one'), (2, 'two'), (3, 'three'), (4, 'four')] def sortItem(pair): return pair[1] pairs.sort(key=sortItem) print pairs # The result is just the same, but our syntax is shorter and self-descriptive. # But remember, lambdax could handle only single expression, for more powerful # caluclation you still need a full function.