Constants and precalculated expressions for drivers (or custom script)

Hello. As you can see on the screenshot, expression «degrees(z)» enters 2 times and constant 110 too. And there is no way to precalculate degrees(z) once or set const 110 right in the driver. Yes, constant or variable can be made with custom properties. Sometimes it is handy. In other cases is not. Also precalculation of sub-expression will make code faster and allow to cut it into smaller pieces without need to create custom properties out of driver.

The other ultimate way — is just adding ability to use multistring script. Is it possible now? It don`t look like this, but I feel there can be a trick.