python/luhn: download exercise

python/luhn/.exercism/config.json

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+{
+  "authors": [
+    "sjakobi"
+  ],
+  "contributors": [
+    "AnAccountForReportingBugs",
+    "behrtam",
+    "BethanyG",
+    "cmccandless",
+    "Dog",
+    "Grociu",
+    "ikhadykin",
+    "kytrinyx",
+    "mambocab",
+    "N-Parsons",
+    "Nishant23",
+    "olufotebig",
+    "pheanex",
+    "rootulp",
+    "thomasjpfan",
+    "tqa236",
+    "xitanggg",
+    "yawpitch"
+  ],
+  "files": {
+    "solution": [
+      "luhn.py"
+    ],
+    "test": [
+      "luhn_test.py"
+    ],
+    "example": [
+      ".meta/example.py"
+    ]
+  },
+  "blurb": "Given a number determine whether or not it is valid per the Luhn formula.",
+  "source": "The Luhn Algorithm on Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Luhn_algorithm"
+}

python/luhn/.exercism/metadata.json

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+{"track":"python","exercise":"luhn","id":"fda87fb1d5324fef81e9bfc025d2666e","url":"https://exercism.org/tracks/python/exercises/luhn","handle":"vpayno","is_requester":true,"auto_approve":false}

python/luhn/HELP.md

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+# Help
+
+## Running the tests
+
+We use [pytest][pytest: Getting Started Guide] as our website test runner.
+You will need to install `pytest` on your development machine if you want to run tests for the Python track locally.
+You should also install the following `pytest` plugins:
+
+- [pytest-cache][pytest-cache]
+- [pytest-subtests][pytest-subtests]
+
+Extended information can be found in our website [Python testing guide][Python track tests page].
+
+
+### Running Tests
+
+To run the included tests, navigate to the folder where the exercise is stored using `cd` in your terminal (_replace `{exercise-folder-location}` below with your path_).
+Test files usually end in `_test.py`, and are the same tests that run on the website when a solution is uploaded.
+
+Linux/MacOS
+```bash
+$ cd {path/to/exercise-folder-location}
+```
+
+Windows
+```powershell
+PS C:\Users\foobar> cd {path\to\exercise-folder-location}
+```
+
+<br>
+
+Next, run the `pytest` command in your terminal, replacing `{exercise_test.py}` with the name of the test file:
+
+Linux/MacOS
+```bash
+$ python3 -m pytest -o markers=task {exercise_test.py}
+==================== 7 passed in 0.08s ====================
+```
+
+Windows
+```powershell
+PS C:\Users\foobar> py -m pytest -o markers=task {exercise_test.py}
+==================== 7 passed in 0.08s ====================
+```
+
+
+### Common options
+- `-o` : override default `pytest.ini` (_you can use this to avoid marker warnings_)
+- `-v` : enable verbose output.
+- `-x` : stop running tests on first failure.
+- `--ff` : run failures from previous test before running other test cases.
+
+For additional options, use `python3 -m pytest -h` or `py -m pytest -h`.
+
+
+### Fixing warnings
+
+If you do not use `pytest -o markers=task` when invoking `pytest`, you might receive a `PytestUnknownMarkWarning` for tests that use our new syntax:
+
+```bash
+PytestUnknownMarkWarning: Unknown pytest.mark.task - is this a typo?  You can register custom marks to avoid this warning - for details, see https://docs.pytest.org/en/stable/mark.html
+```
+
+To avoid typing `pytest -o markers=task` for every test you run, you can use a `pytest.ini` configuration file.
+We have made one that can be downloaded from the top level of the Python track directory: [pytest.ini][pytest.ini].
+
+You can also create your own `pytest.ini` file with the following content:
+
+```ini
+[pytest]
+markers =
+    task: A concept exercise task.
+```
+
+Placing the `pytest.ini` file in the _root_ or _working_ directory for your Python track exercises will register the marks and stop the warnings.
+More information on pytest marks can be found in the `pytest` documentation on [marking test functions][pytest: marking test functions with attributes] and the `pytest` documentation on [working with custom markers][pytest: working with custom markers].
+
+Information on customizing pytest configurations can be found in the `pytest` documentation on [configuration file formats][pytest: configuration file formats].
+
+
+### Extending your IDE or Code Editor
+
+Many IDEs and code editors have built-in support for using `pytest` and other code quality tools.
+Some community-sourced options can be found on our [Python track tools page][Python track tools page].
+
+[Pytest: Getting Started Guide]: https://docs.pytest.org/en/latest/getting-started.html
+[Python track tools page]: https://exercism.org/docs/tracks/python/tools
+[Python track tests page]: https://exercism.org/docs/tracks/python/tests
+[pytest-cache]:http://pythonhosted.org/pytest-cache/
+[pytest-subtests]:https://github.com/pytest-dev/pytest-subtests
+[pytest.ini]: https://github.com/exercism/python/blob/main/pytest.ini
+[pytest: configuration file formats]: https://docs.pytest.org/en/6.2.x/customize.html#configuration-file-formats
+[pytest: marking test functions with attributes]: https://docs.pytest.org/en/6.2.x/mark.html#raising-errors-on-unknown-marks
+[pytest: working with custom markers]: https://docs.pytest.org/en/6.2.x/example/markers.html#working-with-custom-markers
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit luhn.py` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [Python track's documentation](https://exercism.org/docs/tracks/python)
+- The [Python track's programming category on the forum](https://forum.exercism.org/c/programming/python)
+- [Exercism's programming category on the forum](https://forum.exercism.org/c/programming/5)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+Below are some resources for getting help if you run into trouble:
+
+- [The PSF](https://www.python.org) hosts Python downloads, documentation, and community resources.
+- [The Exercism Community on Discord](https://exercism.org/r/discord)
+- [Python Community on Discord](https://pythondiscord.com/) is a very helpful and active community.
+- [/r/learnpython/](https://www.reddit.com/r/learnpython/) is a subreddit designed for Python learners.
+- [#python on Libera.chat](https://www.python.org/community/irc/) this is where the core developers for the language hang out and get work done.
+- [Python Community Forums](https://discuss.python.org/)
+- [Free Code Camp Community Forums](https://forum.freecodecamp.org/)
+- [CodeNewbie Community Help Tag](https://community.codenewbie.org/t/help)
+- [Pythontutor](http://pythontutor.com/) for stepping through small code snippets visually.
+
+Additionally, [StackOverflow](http://stackoverflow.com/questions/tagged/python) is a good spot to search for your problem/question to see if it has been answered already.
+ If not - you can always [ask](https://stackoverflow.com/help/how-to-ask) or [answer](https://stackoverflow.com/help/how-to-answer) someone else's question.

python/luhn/README.md

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+# Luhn
+
+Welcome to Luhn on Exercism's Python Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## Instructions
+
+Given a number determine whether or not it is valid per the Luhn formula.
+
+The [Luhn algorithm][luhn] is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers and Canadian Social Insurance Numbers.
+
+The task is to check if a given string is valid.
+
+## Validating a Number
+
+Strings of length 1 or less are not valid.
+Spaces are allowed in the input, but they should be stripped before checking.
+All other non-digit characters are disallowed.
+
+### Example 1: valid credit card number
+
+```text
+4539 3195 0343 6467
+```
+
+The first step of the Luhn algorithm is to double every second digit, starting from the right.
+We will be doubling
+
+```text
+4_3_ 3_9_ 0_4_ 6_6_
+```
+
+If doubling the number results in a number greater than 9 then subtract 9 from the product.
+The results of our doubling:
+
+```text
+8569 6195 0383 3437
+```
+
+Then sum all of the digits:
+
+```text
+8+5+6+9+6+1+9+5+0+3+8+3+3+4+3+7 = 80
+```
+
+If the sum is evenly divisible by 10, then the number is valid.
+This number is valid!
+
+### Example 2: invalid credit card number
+
+```text
+8273 1232 7352 0569
+```
+
+Double the second digits, starting from the right
+
+```text
+7253 2262 5312 0539
+```
+
+Sum the digits
+
+```text
+7+2+5+3+2+2+6+2+5+3+1+2+0+5+3+9 = 57
+```
+
+57 is not evenly divisible by 10, so this number is not valid.
+
+[luhn]: https://en.wikipedia.org/wiki/Luhn_algorithm
+
+## Source
+
+### Created by
+
+- @sjakobi
+
+### Contributed to by
+
+- @AnAccountForReportingBugs
+- @behrtam
+- @BethanyG
+- @cmccandless
+- @Dog
+- @Grociu
+- @ikhadykin
+- @kytrinyx
+- @mambocab
+- @N-Parsons
+- @Nishant23
+- @olufotebig
+- @pheanex
+- @rootulp
+- @thomasjpfan
+- @tqa236
+- @xitanggg
+- @yawpitch
+
+### Based on
+
+The Luhn Algorithm on Wikipedia - https://en.wikipedia.org/wiki/Luhn_algorithm

python/luhn/luhn.py

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+class Luhn:
+    def __init__(self, card_num):
+        pass
+
+    def valid(self):
+        pass

python/luhn/luhn_test.py

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+# These tests are auto-generated with test data from:
+# https://github.com/exercism/problem-specifications/tree/main/exercises/luhn/canonical-data.json
+# File last updated on 2023-07-19
+
+import unittest
+
+from luhn import (
+    Luhn,
+)
+
+
+class LuhnTest(unittest.TestCase):
+    def test_single_digit_strings_can_not_be_valid(self):
+        self.assertIs(Luhn("1").valid(), False)
+
+    def test_a_single_zero_is_invalid(self):
+        self.assertIs(Luhn("0").valid(), False)
+
+    def test_a_simple_valid_sin_that_remains_valid_if_reversed(self):
+        self.assertIs(Luhn("059").valid(), True)
+
+    def test_a_simple_valid_sin_that_becomes_invalid_if_reversed(self):
+        self.assertIs(Luhn("59").valid(), True)
+
+    def test_a_valid_canadian_sin(self):
+        self.assertIs(Luhn("055 444 285").valid(), True)
+
+    def test_invalid_canadian_sin(self):
+        self.assertIs(Luhn("055 444 286").valid(), False)
+
+    def test_invalid_credit_card(self):
+        self.assertIs(Luhn("8273 1232 7352 0569").valid(), False)
+
+    def test_invalid_long_number_with_an_even_remainder(self):
+        self.assertIs(Luhn("1 2345 6789 1234 5678 9012").valid(), False)
+
+    def test_invalid_long_number_with_a_remainder_divisible_by_5(self):
+        self.assertIs(Luhn("1 2345 6789 1234 5678 9013").valid(), False)
+
+    def test_valid_number_with_an_even_number_of_digits(self):
+        self.assertIs(Luhn("095 245 88").valid(), True)
+
+    def test_valid_number_with_an_odd_number_of_spaces(self):
+        self.assertIs(Luhn("234 567 891 234").valid(), True)
+
+    def test_valid_strings_with_a_non_digit_added_at_the_end_become_invalid(self):
+        self.assertIs(Luhn("059a").valid(), False)
+
+    def test_valid_strings_with_punctuation_included_become_invalid(self):
+        self.assertIs(Luhn("055-444-285").valid(), False)
+
+    def test_valid_strings_with_symbols_included_become_invalid(self):
+        self.assertIs(Luhn("055# 444$ 285").valid(), False)
+
+    def test_single_zero_with_space_is_invalid(self):
+        self.assertIs(Luhn(" 0").valid(), False)
+
+    def test_more_than_a_single_zero_is_valid(self):
+        self.assertIs(Luhn("0000 0").valid(), True)
+
+    def test_input_digit_9_is_correctly_converted_to_output_digit_9(self):
+        self.assertIs(Luhn("091").valid(), True)
+
+    def test_very_long_input_is_valid(self):
+        self.assertIs(Luhn("9999999999 9999999999 9999999999 9999999999").valid(), True)
+
+    def test_valid_luhn_with_an_odd_number_of_digits_and_non_zero_first_digit(self):
+        self.assertIs(Luhn("109").valid(), True)
+
+    def test_using_ascii_value_for_non_doubled_non_digit_isn_t_allowed(self):
+        self.assertIs(Luhn("055b 444 285").valid(), False)
+
+    def test_using_ascii_value_for_doubled_non_digit_isn_t_allowed(self):
+        self.assertIs(Luhn(":9").valid(), False)
+
+    def test_non_numeric_non_space_char_in_the_middle_with_a_sum_that_s_divisible_by_10_isn_t_allowed(
+        self,
+    ):
+        self.assertIs(Luhn("59%59").valid(), False)
+
+    # Additional tests for this track
+
+    def test_is_valid_can_be_called_repeatedly(self):
+        # This test was added, because we saw many implementations
+        # in which the first call to valid() worked, but the
+        # second call failed().
+        number = Luhn("055 444 285")
+        self.assertIs(number.valid(), True)
+        self.assertIs(number.valid(), True)