Hello i'm not gonna write a long topic,
You want a simple minimalist code to use a Nextion screen with Node.js & Python (my code is better on Node.js !). If you want, here is a little code to control your screen with a Raspberry :
This is not a Node module, just an example, you can use my code directly into your program.
Don't forget to change the SerialPort in client.js "var port = new SerialPort('/dev/ttyAMA0'"
You can add some command directly into "write" object, or you can use "write.uart" if you don't want to. Post any issue if you have one, i will respond to you on Github or on this forum.
Sorry for my english, i'm a french dev !
Good luck with your project (with just this little code i have a 500 lines code to use my screen as home automation)