food chain exercise

python/food-chain/.exercism/metadata.json

@@ -0,0 +1 @@
+{"track":"python","exercise":"food-chain","id":"b890dc4d044149a7bfbd854912c68bbf","url":"https://exercism.io/my/solutions/b890dc4d044149a7bfbd854912c68bbf","handle":"Xevion","is_requester":true,"auto_approve":false}

python/food-chain/README.md

@@ -0,0 +1,113 @@
+# Food Chain
+
+Generate the lyrics of the song 'I Know an Old Lady Who Swallowed a Fly'.
+
+While you could copy/paste the lyrics,
+or read them from a file, this problem is much more
+interesting if you approach it algorithmically.
+
+This is a [cumulative song](http://en.wikipedia.org/wiki/Cumulative_song) of unknown origin.
+
+This is one of many common variants.
+
+```text
+I know an old lady who swallowed a fly.
+I don't know why she swallowed the fly. Perhaps she'll die.
+
+I know an old lady who swallowed a spider.
+It wriggled and jiggled and tickled inside her.
+She swallowed the spider to catch the fly.
+I don't know why she swallowed the fly. Perhaps she'll die.
+
+I know an old lady who swallowed a bird.
+How absurd to swallow a bird!
+She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
+She swallowed the spider to catch the fly.
+I don't know why she swallowed the fly. Perhaps she'll die.
+
+I know an old lady who swallowed a cat.
+Imagine that, to swallow a cat!
+She swallowed the cat to catch the bird.
+She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
+She swallowed the spider to catch the fly.
+I don't know why she swallowed the fly. Perhaps she'll die.
+
+I know an old lady who swallowed a dog.
+What a hog, to swallow a dog!
+She swallowed the dog to catch the cat.
+She swallowed the cat to catch the bird.
+She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
+She swallowed the spider to catch the fly.
+I don't know why she swallowed the fly. Perhaps she'll die.
+
+I know an old lady who swallowed a goat.
+Just opened her throat and swallowed a goat!
+She swallowed the goat to catch the dog.
+She swallowed the dog to catch the cat.
+She swallowed the cat to catch the bird.
+She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
+She swallowed the spider to catch the fly.
+I don't know why she swallowed the fly. Perhaps she'll die.
+
+I know an old lady who swallowed a cow.
+I don't know how she swallowed a cow!
+She swallowed the cow to catch the goat.
+She swallowed the goat to catch the dog.
+She swallowed the dog to catch the cat.
+She swallowed the cat to catch the bird.
+She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
+She swallowed the spider to catch the fly.
+I don't know why she swallowed the fly. Perhaps she'll die.
+
+I know an old lady who swallowed a horse.
+She's dead, of course!
+```
+
+## 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 the appropriate command below ([why they are different](https://github.com/pytest-dev/pytest/issues/1629#issue-161422224)):
+
+- Python 2.7: `py.test food_chain_test.py`
+- Python 3.4+: `pytest food_chain_test.py`
+
+Alternatively, you can tell Python to run the pytest module (allowing the same command to be used regardless of Python version):
+`python -m pytest food_chain_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/food-chain` 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
+
+Wikipedia [http://en.wikipedia.org/wiki/There_Was_an_Old_Lady_Who_Swallowed_a_Fly](http://en.wikipedia.org/wiki/There_Was_an_Old_Lady_Who_Swallowed_a_Fly)
+
+## Submitting Incomplete Solutions
+
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

python/food-chain/food_chain.py

@@ -0,0 +1,53 @@
+intro = "I know an old lady who swallowed a {}."
+intro_addendums = [
+    "It wriggled and jiggled and tickled inside her.",
+    "How absurd to swallow a bird!",
+    "Imagine that, to swallow a cat!",
+    "What a hog, to swallow a dog!",
+    "Just opened her throat and swallowed a goat!",
+    "I don't know how she swallowed a cow!"
+]
+names = [
+    "fly",
+    "spider",
+    "bird",
+    "cat",
+    "dog",
+    "goat",
+    "cow",
+    "horse"
+]
+
+middle = "She swallowed the {} to catch the {}."
+outro = "I don't know why she swallowed the fly. Perhaps she'll die."
+last = "She\'s dead, of course!"
+special_middle = "that wriggled and jiggled and tickled inside her"
+
+# Just does the math for constructing single and multiple verses. I realized only halfway through that
+# everything was going to be in lists, so I just used split, which honestly is easier than needing some kind of flattening
+# or list extending setup to get the lists to be in proper order
+def recite(start_verse, end_verse):
+    if start_verse == end_verse:
+        return construct(start_verse - 1).split('\n')
+    return '\n\n'.join(construct(verse) for verse in range(start_verse - 1, end_verse)).split('\n')
+
+# Constructs a specific verse
+def construct(verse):
+    # Constructs the middle part. Only the spider verse makes this function required.
+    def makemiddle(versen):
+        # Special spider inner verse
+        if versen == 2:
+            return middle.format(names[versen], names[versen-1] + ' ' + special_middle)
+        return middle.format(names[versen], names[versen-1])
+    # Horse verse
+    if verse == 7:
+        return "{}\n{}".format(intro.format(names[verse]), last)
+    # Constructs the intoduction of a verse
+    constructed_intro = '{}{}'.format(
+        intro.format(names[verse]),
+        '\n' + intro_addendums[verse-1] if verse > 0 else ''
+    )
+    # Constructs the middle verse using make middle
+    constructed_middle = '\n'.join([''] + [makemiddle(versen) for versen in range(verse, 0, -1)]) if verse >= 1 else ''
+    # Finally constructs the entire properly.
+    return "{}{}{}".format(constructed_intro, constructed_middle, '\n' + outro)

python/food-chain/food_chain_test.py

@@ -0,0 +1,111 @@
+import unittest
+
+from food_chain import recite
+
+
+# Tests adapted from `problem-specifications//canonical-data.json` @ v2.1.0
+
+class FoodChainTest(unittest.TestCase):
+
+    def test_fly(self):
+        expected = [
+            "I know an old lady who swallowed a fly.",
+            "I don't know why she swallowed the fly. Perhaps she'll die.",
+        ]
+        self.assertEqual(recite(1, 1), expected)
+
+    def test_spider(self):
+        expected = [
+            "I know an old lady who swallowed a spider.",
+            "It wriggled and jiggled and tickled inside her.",
+            "She swallowed the spider to catch the fly.",
+            "I don't know why she swallowed the fly. Perhaps she'll die.",
+        ]
+        self.assertEqual(recite(2, 2), expected)
+
+    def test_bird(self):
+        expected = [
+            "I know an old lady who swallowed a bird.",
+            "How absurd to swallow a bird!",
+            "She swallowed the bird to catch the spider that "
+            "wriggled and jiggled and tickled inside her.",
+            "She swallowed the spider to catch the fly.",
+            "I don't know why she swallowed the fly. Perhaps she'll die.",
+        ]
+        self.assertEqual(recite(3, 3), expected)
+
+    def test_cat(self):
+        expected = [
+            "I know an old lady who swallowed a cat.",
+            "Imagine that, to swallow a cat!",
+            "She swallowed the cat to catch the bird.",
+            "She swallowed the bird to catch the spider that "
+            "wriggled and jiggled and tickled inside her.",
+            "She swallowed the spider to catch the fly.",
+            "I don't know why she swallowed the fly. Perhaps she'll die.",
+        ]
+        self.assertEqual(recite(4, 4), expected)
+
+    def test_dog(self):
+        expected = [
+            "I know an old lady who swallowed a dog.",
+            "What a hog, to swallow a dog!",
+            "She swallowed the dog to catch the cat.",
+            "She swallowed the cat to catch the bird.",
+            "She swallowed the bird to catch the spider that wriggled "
+            "and jiggled and tickled inside her.",
+            "She swallowed the spider to catch the fly.",
+            "I don't know why she swallowed the fly. Perhaps she'll die.",
+        ]
+        self.assertEqual(recite(5, 5), expected)
+
+    def test_goat(self):
+        expected = [
+            "I know an old lady who swallowed a goat.",
+            "Just opened her throat and swallowed a goat!",
+            "She swallowed the goat to catch the dog.",
+            "She swallowed the dog to catch the cat.",
+            "She swallowed the cat to catch the bird.",
+            "She swallowed the bird to catch the spider that "
+            "wriggled and jiggled and tickled inside her.",
+            "She swallowed the spider to catch the fly.",
+            "I don't know why she swallowed the fly. Perhaps she'll die.",
+        ]
+        self.assertEqual(recite(6, 6), expected)
+
+    def test_cow(self):
+        expected = [
+            "I know an old lady who swallowed a cow.",
+            "I don't know how she swallowed a cow!",
+            "She swallowed the cow to catch the goat.",
+            "She swallowed the goat to catch the dog.",
+            "She swallowed the dog to catch the cat.",
+            "She swallowed the cat to catch the bird.",
+            "She swallowed the bird to catch the spider that "
+            "wriggled and jiggled and tickled inside her.",
+            "She swallowed the spider to catch the fly.",
+            "I don't know why she swallowed the fly. Perhaps she'll die.",
+        ]
+        self.assertEqual(recite(7, 7), expected)
+
+    def test_horse(self):
+        expected = [
+            "I know an old lady who swallowed a horse.",
+            "She's dead, of course!",
+        ]
+        self.assertEqual(recite(8, 8), expected)
+
+    def test_multiple_verses(self):
+        expected = recite(1, 1) + [""] + recite(2, 2) + [""] + recite(3, 3)
+        self.assertEqual(recite(1, 3), expected)
+
+    def test_full_song(self):
+        expected = []
+        for n in range(1, 9):
+            expected += recite(n, n) + [""]
+        expected.pop()
+        self.assertEqual(recite(1, 8), expected)
+
+
+if __name__ == '__main__':
+    unittest.main()