diff --git a/exercises/ex04/help.py b/exercises/ex04/help.py
old mode 100644
new mode 100755
index 3e60b3c..acc4571
--- a/exercises/ex04/help.py
+++ b/exercises/ex04/help.py
@@ -1,3 +1,4 @@
+#!/usr/bin/env python
 # Exercise 4
 # help arg 
 # 1. Getting help with -help or -h.
diff --git a/exercises/ex05/cat.py b/exercises/ex05/cat.py
old mode 100644
new mode 100755
index 6b3916f..3d8d40a
--- a/exercises/ex05/cat.py
+++ b/exercises/ex05/cat.py
@@ -1,3 +1,4 @@
+#!/usr/bin/env python
 # Exercise 5
 # cat command
 
diff --git a/exercises/ex06/find.py b/exercises/ex06/find.py
old mode 100644
new mode 100755
index 1c45d64..8643309
--- a/exercises/ex06/find.py
+++ b/exercises/ex06/find.py
@@ -1,3 +1,4 @@
+#!/usr/bin/env python
 # Exercise 6
 # find command
 
diff --git a/exercises/ex07/grep.py b/exercises/ex07/grep.py
old mode 100644
new mode 100755
index db1d27e..4f92a54
--- a/exercises/ex07/grep.py
+++ b/exercises/ex07/grep.py
@@ -1,3 +1,4 @@
+#!/usr/bin/env python
 # Exercise 7
 # grep command
 
diff --git a/exercises/ex08/cut.py b/exercises/ex08/cut.py
old mode 100644
new mode 100755
index a6896ed..98eee49
--- a/exercises/ex08/cut.py
+++ b/exercises/ex08/cut.py
@@ -1,3 +1,4 @@
+#!/usr/bin/env python
 # Exercise 8
 # cut command
 
diff --git a/exercises/ex09/sed.py b/exercises/ex09/sed.py
old mode 100644
new mode 100755
index 37100c2..27c99c7
--- a/exercises/ex09/sed.py
+++ b/exercises/ex09/sed.py
@@ -1,3 +1,4 @@
+#!/usr/bin/env python
 # Exercise 9
 # sed command
 
diff --git a/exercises/ex10/sort.py b/exercises/ex10/sort.py
old mode 100644
new mode 100755
index 289fee9..e29a7b9
--- a/exercises/ex10/sort.py
+++ b/exercises/ex10/sort.py
@@ -1,3 +1,4 @@
+#!/usr/bin/env python
 # Exercise 10
 # sort command