Use a mouse to draw on a screen with python? [closed]
You will need to create a transparent widget that covers the screen so that you can draw on it. I don't know how each of the GUI toolkits does this, but I'm sure they all have the functionality necessary to grab the screen's size and create a window that can cover it. With wxPython, you would create a wx.Frame instance and call its SetTransparent method. You can see an example of that here:
The wxPython demo includes a drawing demo that you might also want to take a look at.