We’ve made use of a number of functions so far— everything from
turtle.forward(). But all of these functions have been either built-in or imported from Python modules and libraries. In this chapter, we’ll write our own functions to do anything we want, including responding to user actions like mouse-clicking and keypresses.
Functions are helpful because they give us the ability to organize pieces of reusable code, then refer to those pieces later in our programs by a single short name or command. Take
input() as an example: it prints a text prompt to ask a user for input, collects what the user types, and passes it to our program as a string that we can store in a variable. We ...