fix error couldn't set PYTHONPATH of undefined in VSCode

launch.json

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Python: Current File",
            "type": "python",
            "request": "launch",
            "program": "${file}",
            "console": "integratedTerminal",
            "cwd": "${fileDirname}",
            "env": {
                "PYTHONPATH": "${workspaceFolder}:${env:PYTHONPATH}"
            }
        }
    ]
}

settings.json

{
    "terminal.integrated.env.osx": {
        "PYTHONPATH": "${workspaceFolder}"
    }
}