30 | Rectangle function

What it is is:

rectangle.py

# The rectangle module has functions that perform
# calculations related to rectangles.

# The area function accepts a rectangle's width and
# length as arguments and returns the rectangle's area.
def area(width, length):
    return width * length

# The perimeter function accepts a rectangle's width
# and length as arguments and returns the rectangle's
# perimeter.
def perimeter(width, length):
    return 2 * (width + length)