convert shebang lines: python -> python3
diff --git a/Demo/comparisons/regextest.py b/Demo/comparisons/regextest.py
index d2c534d..547ee0d 100755
--- a/Demo/comparisons/regextest.py
+++ b/Demo/comparisons/regextest.py
@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/env python3
 
 # 1)  Regular Expressions Test
 #
diff --git a/Demo/comparisons/sortingtest.py b/Demo/comparisons/sortingtest.py
index f9ed854..e826e81 100755
--- a/Demo/comparisons/sortingtest.py
+++ b/Demo/comparisons/sortingtest.py
@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/env python3
 
 # 2)  Sorting Test
 #
diff --git a/Demo/comparisons/systemtest.py b/Demo/comparisons/systemtest.py
index e3d840e..8276333 100755
--- a/Demo/comparisons/systemtest.py
+++ b/Demo/comparisons/systemtest.py
@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/env python3
 
 # 3)  System Test
 #