comment about reverse

rasbt · rasbt · commit 6e74774e869e · 2014-08-03T11:32:03.000-04:00
diff --git a/howtos_as_py_files/sort_list_of_tuples_by_ele.py b/howtos_as_py_files/sort_list_of_tuples_by_ele.py
@@ -1,6 +1,5 @@
 # Sebastian Raschka 09/02/2014
-# Sorting a list of tuples by the last elements of the tuple
-
+# Sorting a list of tuples by starting with the last element of the tuple (=reversed tuple)
 
 # Here, we make use of the "key" parameter of the in-built "sorted()" function 
 # (also available for the ".sort()" method), which let's us define a function 
@@ -9,11 +8,27 @@
 # from every tuple.
 
 
-
-a_list = [(1,3,'c'), (2,3,'a'), (1,2,'b')]
+a_list = [(1,3,'c'), (2,3,'a'), (3,2,'b'), (2,2,'b')]
 
 sorted_list = sorted(a_list, key=lambda e: e[::-1])
 
 print(sorted_list)
 
-# prints [(2, 3, 'a'), (1, 2, 'b'), (1, 3, 'c')]
+# prints [(2, 3, 'a'), (2, 2, 'b'), (3, 2, 'b'), (1, 3, 'c')]
+
+
+
+# If we are only interesting in sorting the list by the last element
+# of the tuple and don't care about a "tie" situation, we can also use
+# the index of the tuple item directly instead of reversing the tuple 
+# for efficiency.
+
+
+
+a_list = [(1,3,'c'), (2,3,'a'), (3,2,'b'), (2,2,'b')]
+
+sorted_list = sorted(a_list, key=lambda e: e[-1])
+
+print(sorted_list)
+
+# prints [(2, 3, 'a'), (3, 2, 'b'), (2, 2, 'b'), (1, 3, 'c')]
