E X E R C I S E # 1 4 : A V E R A G E
average([12, 20, 37])
→
23
Averages are an essential statistical tool, and computers make it easy to calculate the average of
millions or billions of numbers. The average is the sum of a set of the numbers divided by the amount
of numbers. For example, the average of 12, 1, and 5 is 6, because 12 + 1 + 5 is 18 and 18 / 3 is 6.
This and the following two exercises challenge you to make Python solve these statistics calculations.
Exercise Description
Write an average() function that has a numbers parameter. This function returns the
statistical average of the list of integer and floating-point numbers passed to the function. While
Python’s built-in sum() function can help you solve this exercise, try writing the solution without
using it.
Passing an empty list to average() should cause it to return None.
These Python assert statements stop the program if their condition is False. Copy them to
the bottom of your solution program. Your solution is correct if the following assert statements’
conditions are all True:
assert average([1, 2, 3]) == 2
assert average([1, 2, 3, 1, 2, 3, 1, 2, 3]) == 2
assert average([12, 20, 37]) == 23
assert average([0, 0, 0, 0, 0]) == 0
import random
random.seed(42)
testData = [1, 2, 3, 1, 2, 3, 1, 2, 3]
for i in range(1000):
random.shuffle(testData)
assert average(testData) == 2
Shuffling the order of the numbers should not affect the average. The for loop does 1,000 such
random shuffles to thoroughly check that this fact remains true. For an explanation of the
random.seed()
function, see the Further Reading section of Exercise #19, ―Password Generator‖.
Try to write a solution based on the information in this description. If you still have trouble
solving this exercise, read the Solution Design and Special Cases and Gotchas sections for
additional hints.
Python Programming Exercises, Gently Explained
45
Prerequisite concepts: len(), for loops, augmented assignment operators
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