No, you wrote that you put #!/usr/bin/python3 as first line in your script. This is not the same. I bet there is no Python binary at this path. This is why you get the file not found error.
No, you wrote that you put #!/usr/bin/python3 as first line in your script. This is not the same. I bet there is no Python binary at this path. This is why you get the file not found error.