Comparing Functions to Methods

In the previous activity, you used the randint function to get a random number when moving the turtle objects forward. Functions allow you to give a name to a set of instructions. You can pass data to a function, and, optionally, you can have it return some data as a result.

Have a look at this example. The following function will tell a knock knock joke if you provide the introduction and the punchline:

def tell(intro, punchline):

    print("Knock knock")

    print("Who's there")

    print(intro)

    print(intro + " who")

    print(punchline)

You could call this function by writing this line of code passing the intro and punchline of the joke:

tell("Atch", "Sounds like you've got a cold!")

When you programmed the turtles, you used methods such as goto(), which are very similar to functions. The difference is that a method is called on an object, which means that as well as being able to receive data from outside, a method can use all of the data stored inside the object as well.

Here’s what the same joke might look like if a Joke object had been defined with a tell() method.

my_joke = Joke("Atch", "Sounds like you've got a cold!")

my_joke.tell()

If you type in this code and try to run it, you will receive an error:

NameError: name 'Joke' is not defined

This is because you have to first tell Python how to create a Joke object. To do this, Python needs a blueprint for the object. The blueprint you create for an object is called a class. You will create your own classes in week two of the course.