Variable not defined even though it is

[CoderMerv]

Looks like you running python from a cmd line in shell and not the script itself.
either do python script.py or if in the interpreter do message = 'my message' then print(message)

Thank you for this. I figured that I just needed to highlight the entire code, then press shift + enter to run it. Previously, I was only pressing shift + enter without highlighting any line of code. This was effectively running just the last line of code.