Naming Sets of Steps¶
How did abs and int get defined? By defining new procedures and functions, we can associate a name with a sequence of steps. Look at the program below. What do you think it will do when you press the Run button? Click Run and see what happens.
If you are wondering why the Run button didn’t seem to do anything, all that the program did was define the procedure
square which takes a
turtle as input. If we want to actually execute the program we need to create a turtle and call the procedure as shown in the next example.
In the above program, we DEFine the word
square to represent the Python statements that draw a square with a turtle. The
square procedure takes as input a
turtle that will be used to draw the square. Notice that the sequence of statements that are part of the
square procedure are indented. Python uses indention to show what statements belong to the procedure. When the indention stops with
from turtle import * it means that the new statements are not part of the procedure.
Notice that we defined the turtle procedure
def square (turtle): in the code above before we tried to call it
square(malik). This is required in Python, but not in some other programming languages.
Defining a Function¶
You define a function just like you define a procedure, but it will also
return a value as shown below.
To return a value from a function use the Python keyword
return followed by the value to return.
Check Your Understanding
See the video below for a hint on how to solve the next mixed up code problem.
The following code should define a procedure that draws a triangle, but it may be mixed up <i>and may contain extra (unused) code</i>. Drag the needed code to the right side in the correct order. <b>Remember that the statements in the procedure must be indented!</b> To indent a block drag it further right.