launch/lesson5.launch.py

+from launch import LaunchDescription
+from launch_ros.actions import Node
+
+def generate_launch_description():
+    return LaunchDescription([
+	Node(
+            package='rqt_plot',
+            namespace='',
+            executable='rqt_plot',
+            name='cons'
+        ),
+        Node(
+            package='turtlesim',
+            namespace='',
+            executable='turtlesim_node',
+            name='sim'
+        ),
+        Node(
+            package='lesson_05',
+            namespace='',
+            executable='step_4',
+            name='square'
+        )
+    ])
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