os.system('cls') is Windows only

[tbroset]

In update_progress() you use os.system('cls'), which is not OS Independent. On a non-Windows system you will get the following errors: tweaker3 -i BODY_RIGHT.stl -x -p sh: cls: command not found Progress is: 18 sh: cls: command not found Progress is: 54 sh: cls: command not found Progress is: 90

I would suggest using something along the lines of os.system('cls' if os.name == 'nt' else 'clear') Reference: https://stackoverflow.com/a/2084628/18731807