Project: Add a surname

Write a function named add_surname that takes a list of first names. It returns a new list holding only the names that start with "K", each with the surname "Hoffman" added after a space. You can assume every name starts with a capital letter. For example, given this list:

["Kiki", "Krystal", "Pavel", "MaryKay", "Annie", "Koala"]

the function returns:

['Kiki Hoffman', 'Krystal Hoffman', 'Koala Hoffman']

Save the file as add_surname.py.

Show a solution

Try the project on your own first. This is one working solution, followed by its tests. Press Run to run the tests. Read them to see what thorough testing looks like, then change the solution and run again to watch a test fail. The testing tools used here (classes and unittest) are not part of the course yet, so do not worry about how they work.

def add_surname(first_names: list) -> list:
    """Return the names starting with "K", each followed by " Hoffman"."""
    return [name + " Hoffman" for name in first_names if name[0] == "K"]

# ---- Tests ----
import sys
import unittest

class TestAddSurname(unittest.TestCase):
    def test_the_example_from_the_project(self):
        names = ["Kiki", "Krystal", "Pavel", "MaryKay", "Annie", "Koala"]
        expected = ["Kiki Hoffman", "Krystal Hoffman", "Koala Hoffman"]
        self.assertEqual(add_surname(names), expected)

def test_an_empty_list_gives_an_empty_list(self):
        self.assertEqual(add_surname([]), [])

def test_a_name_starting_with_k_gets_the_surname(self):
        self.assertEqual(add_surname(["Kim"]), ["Kim Hoffman"])

def test_a_name_not_starting_with_k_is_left_out(self):
        self.assertEqual(add_surname(["Pavel"]), [])

def test_a_k_in_the_middle_of_a_name_does_not_count(self):
        self.assertEqual(add_surname(["MaryKay", "Ik"]), [])

def test_a_lower_case_k_does_not_count(self):
        self.assertEqual(add_surname(["kiki"]), [])

def test_a_single_letter_name_is_handled(self):
        self.assertEqual(add_surname(["K", "A"]), ["K Hoffman"])

def test_names_keep_their_original_order(self):
        self.assertEqual(
            add_surname(["Zed", "Kyle", "Kai", "Ann"]),
            ["Kyle Hoffman", "Kai Hoffman"],
        )

def test_the_original_list_is_left_unchanged(self):
        names = ["Kiki", "Pavel"]
        add_surname(names)
        self.assertEqual(names, ["Kiki", "Pavel"])

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

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