It really depends on what you want to do, some big ones are:
Unreal Development Kit (UDK): udk.com/
Not something i would recommend if you're a beginner, quite difficult to get started with. The coding is done in form of scripting with UnrealScript.
root = tkinter.Tk()
buttons=[i for i in range(10)]
#If specific button is pressed, output "YES"
for num in buttons: