We've now seen two different libraries for writing programs that have graphical user interfaces: PyGame and Tkinter. In exploring these two libraries, we've seen that there are substantial similarities between them, but also substantial differences; both the similarities and the differences are instructive.

When we wrote Tkinter-based user interfaces and we needed to specify what would happen when meaningful input events arose, we tended to write the names of functions, but didn't follow them with parentheses and didn't pass arguments to them, which might have struck you as odd at first. What is it about Tkinter's underlying design that made this the correct choice? What would have happened if we had put in the parentheses and passed the arguments instead?

When we wrote PyGame-based games and we needed to specify what would happen when meaningful input events arose, we instead wrote calls to functions (i.e., we included the parentheses and any applicable arguments). What's different about PyGame's design that made that the right choice, when it's not the right choice in Tkinter?