Function Review
Functions are tricky! It takes a minute to get used to them, but after that they'll be second nature to you. You might find yourself slowing down a bit in this chapter, and if you do, that's totally normal.
Let's break down this function line by line so you can understand every nook and cranny of it.
def area_of_circle(r):
pi = 3.14
result = pi * r * r
return result
radius = 5
area = area_of_circle(radius)
print(area)
# 78.5
Here's a chronological explanation of what happens when the above code is executed:
def area_of_circle(r)
The area_of_circle function is defined for later use, but not called. It accepts a single input, the arbitrarily named r. The body of the function (pi = 3.14... etc) is ignored for now.
radius = 5
A new variable called radius is created and set to the value 5.
area_of_circle(radius)
The area_of_circle function is called with radius (in this case 5) as the input. Finally, we jump back to the function definition.
def area_of_circle(r):
We will now start executing the body of the function, and r is set to 5.
pi = 3.14
A new variable called pi is created with a value of 3.14.
result = pi * r * r
Some simple math is evaluated (3.14 * 5 * 5) and stored in the result variable.
return result
The result variable is returned from the function as output.
area = area_of_circle(radius)
The returned value is stored in a new variable called area (in this case 78.5).
print(area)
The value of area is printed to the console.
Why is the variable called 'radius' outside the function, but 'r' inside the function?