I recently continued my work on my Minecraft Pi programs, and made two changes.
First, I changed the /build command. Now, you right-click the two points, then right-click the block that you want to fill in the space with. Since you cannot right-click air, I also added the /clear command. You right-click both pos 1 and pos 2, and everything in between immediately turns into air (disappears). Then, I added a new command. It's the /tree command. When you run this command, it asks how many trees you want to plant. Then, just right-click anywhere and a tree appears. I even coded it so it will randomly be either an oak tree, or a birch tree! The /tree command can be useful if you are creating a secret hideout with trees, or to just make places naturally beautiful!