Add chapter 5 code companion (#2)

ch05/first-python-package/LICENSE

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+Copyright © 2021 <copyright holders>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

ch05/first-python-package/MANIFEST.in

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+graft src
+recursive-exclude __pycache__ *.py[cod]

ch05/first-python-package/README.md

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+# first-python-package
+
+This package does amazing things.
+
+## Installation
+
+```shell
+$ python -m pip install first-python-package
+```

ch05/first-python-package/pyproject.toml

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+[build-system]
+requires = ["setuptools", "wheel", "cython"]
+build-backend = "setuptools.build_meta"

ch05/first-python-package/setup.cfg

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+[metadata]
+name = first-python-package
+version = 0.0.1
+description = This package does amazing things.
+long_description = file: README.md
+long_description_content_type = text/markdown
+url = https://github.com/daneah/publishing-python-packages
+author = Dane Hillard
+author_email = "Dane Hillard" <github@danehillard.com>
+license = MIT
+license_files = LICENSE
+classifiers =
+    License :: OSI Approved :: MIT License
+
+[options]
+package_dir =
+    =src
+packages = find:
+include_package_data = True
+install_requires =
+    termcolor>=1.1.0,<2
+
+[options.packages.find]
+where = src
+exclude =
+    test*
+
+[options.entry_points]
+console_scripts =
+    harmony = imppkg.harmony:main
+
+######################
+# Tool configuration #
+######################
+
+[tool:pytest]
+testpaths = test
+addopts = --cov --strict-markers
+xfail_strict = True
+
+[coverage:run]
+source = imppkg
+branch = True
+
+[coverage:report]
+show_missing = True
+skip_covered = True
+
+[coverage:paths]
+source =
+    src/imppkg
+    .venv/*/site-packages/imppkg
+
+[tox:tox]
+envlist = py39,py310
+isolated_build = True
+
+[testenv]
+deps =
+    pytest
+    pytest-cov
+commands =
+    pytest {posargs}

ch05/first-python-package/setup.py

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+from setuptools import setup
+
+from Cython.Build import cythonize
+
+setup(
+    ext_modules=cythonize("src/imppkg/harmonic_mean.pyx"),
+)

ch05/first-python-package/src/imppkg/harmonic_mean.pyx

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+def harmonic_mean(nums):
+    return len(nums) / sum(1 / num for num in nums)

ch05/first-python-package/src/imppkg/harmony.py

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+import sys
+
+from termcolor import cprint
+
+from imppkg.harmonic_mean import harmonic_mean
+
+
+def main():
+    result = 0.0
+
+    try:
+        nums = [float(num) for num in sys.argv[1:]]
+    except ValueError:
+        nums = []
+
+    try:
+        result = harmonic_mean(nums)
+    except ZeroDivisionError:
+        pass
+
+    cprint(result, 'red', 'on_cyan', attrs=['bold'])

ch05/first-python-package/test/test_harmonic_mean.py

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+import sys
+
+import pytest
+from termcolor import colored
+
+from imppkg.harmony import main
+
+
+@pytest.mark.parametrize(
+    "inputs, expected",
+    [
+        (["3", "3", "3"], 3.0),
+        ([], 0.0),
+        (["foo", "bar"], 0.0),
+    ],
+)
+def test_harmony_parametrized(inputs, monkeypatch, capsys, expected):
+    monkeypatch.setattr(sys, "argv", ["harmony"] + inputs)
+    main()
+    assert capsys.readouterr().out.strip() == colored(expected, "red", "on_cyan", attrs=["bold"])
+
+
+FRUITS = ["apple"]
+
+
+def test_len():
+    assert len(FRUITS) == 1
+
+
+def test_append():
+    FRUITS.append("banana")
+    assert FRUITS == ["apple", "banana"]