Project: Average of five numbers

Write a program that reads five numbers from the keyboard and prints their average. It should accept negative numbers and decimals. When you run it, the output should match this format:

Please enter five numbers.
-5.4
2.1
7.0
134.8
-20.0
The calculated average of those numbers is:
23.7

Save the file as calculate_average.py.

Show a solution

Try the project on your own first. This is one working solution. Press Run, and a box asks for each input. Type the sample values from the project description to see the same output.

These tests check the solution above. They run a copy of the program, kept in PROGRAM, and give it pretend input. The testing tools here are not part of the course yet, so do not worry about how they work. Read the test names and the expected outputs: together they list what the program must do. Press Run to run the tests.

PROGRAM = r'''
print("Please enter five numbers.")
first = float(input())
second = float(input())
third = float(input())
fourth = float(input())
fifth = float(input())

average = (first + second + third + fourth + fifth) / 5
print("The calculated average of those numbers is:")
print(average)
'''

# ---- Tests ----
import io
import sys
import unittest
from contextlib import redirect_stdout
from unittest import mock

def run_program(*typed_lines: str) -> str:
    """Run the program as if the user typed each line, and return what it printed."""
    answers = iter(typed_lines)

def fake_input(prompt: str = "") -> str:
        print(prompt, end="")
        return next(answers)

output = io.StringIO()
    with mock.patch("builtins.input", fake_input), redirect_stdout(output):
        exec(compile(PROGRAM.strip(), "solution.py", "exec"), {})
    return output.getvalue()

class TestAverageOfFive(unittest.TestCase):
    def test_matches_the_sample_run_exactly(self):
        output = run_program("-5.4", "2.1", "7.0", "134.8", "-20.0")
        self.assertEqual(
            output,
            "Please enter five numbers.\n"
            "The calculated average of those numbers is:\n"
            "23.7\n",
        )

def test_averages_whole_numbers(self):
        output = run_program("1", "2", "3", "4", "5")
        self.assertTrue(output.endswith("is:\n3.0\n"))

def test_five_equal_numbers_average_to_that_number(self):
        output = run_program("7", "7", "7", "7", "7")
        self.assertTrue(output.endswith("is:\n7.0\n"))

def test_accepts_negative_numbers(self):
        output = run_program("-10", "-20", "-30", "-40", "-50")
        self.assertTrue(output.endswith("is:\n-30.0\n"))

def test_positive_and_negative_numbers_cancel_out(self):
        output = run_program("5", "-5", "10", "-10", "0")
        self.assertTrue(output.endswith("is:\n0.0\n"))

def test_accepts_decimals(self):
        output = run_program("0.5", "1.5", "2.5", "3.5", "4.5")
        self.assertTrue(output.endswith("is:\n2.5\n"))

def test_every_number_counts_toward_the_average(self):
        # Moving the single nonzero number to each position gives the same result.
        for position in range(5):
            typed = ["0"] * 5
            typed[position] = "10"
            with self.subTest(position=position):
                self.assertTrue(run_program(*typed).endswith("is:\n2.0\n"))

# ---- Run the tests ----
loader = unittest.defaultTestLoader
suite = unittest.TestSuite(loader.loadTestsFromTestCase(case) for case in [TestAverageOfFive])
unittest.TextTestRunner(stream=sys.stdout, verbosity=2).run(suite)

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