add: resistor-color

python/resistor-color/README.md

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+# Resistor Color
+
+Resistors have color coded bands, where each color maps to a number. The first 2 bands of a resistor have a simple encoding scheme: each color maps to a single number.
+
+These colors are encoded as follows:
+
+- Black: 0
+- Brown: 1
+- Red: 2
+- Orange: 3
+- Yellow: 4
+- Green: 5
+- Blue: 6
+- Violet: 7
+- Grey: 8
+- White: 9
+
+Mnemonics map the colors to the numbers, that, when stored as an array, happen to map to their index in the array: Better Be Right Or Your Great Big Values Go Wrong.
+
+More information on the color encoding of resistors can be found in the [Electronic color code Wikipedia article](https://en.wikipedia.org/wiki/Electronic_color_code)
+
+## Exception messages
+
+Sometimes it is necessary to raise an exception. When you do this, you should include a meaningful error message to
+indicate what the source of the error is. This makes your code more readable and helps significantly with debugging. Not
+every exercise will require you to raise an exception, but for those that do, the tests will only pass if you include
+a message.
+
+To raise a message with an exception, just write it as an argument to the exception type. For example, instead of
+`raise Exception`, you should write:
+
+```python
+raise Exception("Meaningful message indicating the source of the error")
+```
+
+## Running the tests
+
+To run the tests, run `pytest resistor_color_test.py`
+
+Alternatively, you can tell Python to run the pytest module:
+`python -m pytest resistor_color_test.py`
+
+### Common `pytest` options
+
+- `-v` : enable verbose output
+- `-x` : stop running tests on first failure
+- `--ff` : run failures from previous test before running other test cases
+
+For other options, see `python -m pytest -h`
+
+## Submitting Exercises
+
+Note that, when trying to submit an exercise, make sure the solution is in the `$EXERCISM_WORKSPACE/python/resistor-color` directory.
+
+You can find your Exercism workspace by running `exercism debug` and looking for the line that starts with `Workspace`.
+
+For more detailed information about running tests, code style and linting,
+please see [Running the Tests](http://exercism.io/tracks/python/tests).
+
+## Source
+
+Maud de Vries, Erik Schierboom [https://github.com/exercism/problem-specifications/issues/1458](https://github.com/exercism/problem-specifications/issues/1458)
+
+## Submitting Incomplete Solutions
+
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

python/resistor-color/resistor_color.py

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+COLORS = [
+    "black",
+    "brown",
+    "red",
+    "orange",
+    "yellow",
+    "green",
+    "blue",
+    "violet",
+    "grey",
+    "white",
+]
+COLORS_MAPPING = {name: idx for idx, name in enumerate(COLORS)}
+
+
+def color_code(color):
+    return COLORS_MAPPING[color]
+
+
+def colors():
+    return COLORS

python/resistor-color/resistor_color_test.py

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+import unittest
+
+from resistor_color import color_code, colors
+
+# Tests adapted from `problem-specifications//canonical-data.json` @ v1.0.0
+
+
+class ResistorColorTest(unittest.TestCase):
+    def test_black(self):
+        self.assertEqual(color_code("black"), 0)
+
+    def test_white(self):
+        self.assertEqual(color_code("white"), 9)
+
+    def test_orange(self):
+        self.assertEqual(color_code("orange"), 3)
+
+    def test_colors(self):
+        expected = [
+            "black",
+            "brown",
+            "red",
+            "orange",
+            "yellow",
+            "green",
+            "blue",
+            "violet",
+            "grey",
+            "white",
+        ]
+        self.assertEqual(colors(), expected)
+
+
+if __name__ == "__main__":
+    unittest.main()