Exercise2.1 Error - cannot launch python node

ERROR: cannot launch node of type [exercise21/move_robot.py]: can’t locate node [move_robot.py] in package [exercise21]
I have tried all possible best to solve it myself
Below is the screenshot of how my directory looks.

Also i did not create launch and src folders initially but later did. Is it compulsory it is done.
i did:
source devel/setup.bash
I used roslaunch exercise21 move.launch to run my file.

I do not know how it does not work for me. thanks

Hi @jimohafeezco,

Please check out the post below for the solution: