How to Select Node/Object in Scene by script + Clear all Selections by script?

So theres two scripts I need, 1 is to simply select an object/note in my scene and the other is to clear all selections in my scene. 

The goal is to first clear all selections in my scene and then select the required node/object so that I can apply stuff like materials, presets, other custom script actions without having to Find & select the object myself from the scene. 

I am a total newbie with stuff like this so any help is much appreciated.