diff --git a/non-ros-files/Programming_Rules.md b/non-ros-files/Programming_Rules.md
index de2ecc1..f84f56c 100644
--- a/non-ros-files/Programming_Rules.md
+++ b/non-ros-files/Programming_Rules.md
@@ -1,4 +1,4 @@
-# Rules for programming Python in ROS2
+# Rules for programming with Python in ROS2
 ## File Structure
 ```
 colcon_workspace  
@@ -8,12 +8,12 @@ colcon_workspace
       |- src       (contains your source code - this is where you work)
 ```
 
-## Colcon build
+## Colcon Build
 Performing a `colcon build` is neccessary after every change to the `src` directory. This must be performed in the `root` of the _colcon_ workspace (eg. `cd ~/colcon_ws`).
 
 In order to avoid this procedure after every change made to a Python script you must run `colcon build --symlink-install` once. This links the files created in `/build` and `/install` to your source files in `/src`. However, after creating a new Python script this procedure must be repeated in order to also link this new script.
 
-## Source directory
+## Source Directory
 The source directory holds your ROS2 packages as further directories. In this example the `src` directory contains the packages `pubsub` and `pubsub_msg`:
 ```
 colcon_workspace/
@@ -22,4 +22,19 @@ colcon_workspace/
           |
           |- pubsub/
           |- pubsub_msg/
-```
\ No newline at end of file
+```
+
+## setup.py
+The file `<colcon_ws>/<package_dir>/setup.py` defines how to call your scripts using the command line. This results in commands such as  
+`ros2 run pubsub talker`  
+`ros2 run pubsub listener`.  
+This is done by linking the names _talker_ and _listener_  to the Python scripts of your choice, eg.  
+```python
+entry_points={
+   'console_scripts': [
+       'talker = pubsub.talker:main',
+       'listener = pubsub.listener:main'
+   ],
+},
+```  
+