I was trying to change the executer of python in vscode.
I have installed python3 in my system.However default executer of python in vscode is python.So i am getting error as 'python not found' whenever i try to run code. So how could i change the executer to python3 in line no 4066?

I tried to change from user settings. I could change the interpreter there. However i didnt find any way to change the executer.

That's default command Code Runner provides for Python Language.
As long as the execution scripts in terminal when you run python file is python3.8, run code should also use python3.8.
OR you can change the command directly:
"code-runner.executorMap": {
"python": "path/to/python3.8/python.exe -u",
}