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rootulp's solution

to House in the Python Track

Published at Jul 13 2018 · 1 comment
Instructions
Test suite
Solution

Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Recite the nursery rhyme 'This is the House that Jack Built'.

[The] process of placing a phrase of clause within another phrase of clause is called embedding. It is through the processes of recursion and embedding that we are able to take a finite number of forms (words and phrases) and construct an infinite number of expressions. Furthermore, embedding also allows us to construct an infinitely long structure, in theory anyway.

The nursery rhyme reads as follows:

This is the house that Jack built.

This is the malt
that lay in the house that Jack built.

This is the rat
that ate the malt
that lay in the house that Jack built.

This is the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the priest all shaven and shorn
that married the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the rooster that crowed in the morn
that woke the priest all shaven and shorn
that married the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the farmer sowing his corn
that kept the rooster that crowed in the morn
that woke the priest all shaven and shorn
that married the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

This is the horse and the hound and the horn
that belonged to the farmer sowing his corn
that kept the rooster that crowed in the morn
that woke the priest all shaven and shorn
that married the man all tattered and torn
that kissed the maiden all forlorn
that milked the cow with the crumpled horn
that tossed the dog
that worried the cat
that killed the rat
that ate the malt
that lay in the house that Jack built.

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:

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):

  • Python 2.7: py.test house_test.py
  • Python 3.4+: pytest house_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 house_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/house 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 the help page.

Source

British nursery rhyme http://en.wikipedia.org/wiki/This_Is_The_House_That_Jack_Built

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

house_test.py

# Rhyme found in http://www.pitt.edu/~dash/type2035.html

import unittest

from house import recite


# Tests adapted from `problem-specifications//canonical-data.json` @ v2.1.0

class HouseTest(unittest.TestCase):
    def test_verse_one(self):
        expected = ["This is the house that Jack built."]
        self.assertEqual(recite(1, 1), expected)

    def test_verse_two(self):
        expected = [
            "This is the malt"
            "that lay in the house that Jack built."
        ]
        self.assertEqual(recite(2, 2), expected)

    def test_verse_three(self):
        expected = [
            "This is the rat"
            "that ate the malt"
            "that lay in the house that Jack built."
        ]
        self.assertEqual(recite(3, 3), expected)

    def test_verse_four(self):
        expected = [
            "This is the cat"
            "that killed the rat"
            "that ate the malt"
            "that lay in the house that Jack built."
        ]
        self.assertEqual(recite(4, 4), expected)

    def test_verse_five(self):
        expected = [
            "This is the dog"
            "that worried the cat"
            "that killed the rat"
            "that ate the malt"
            "that lay in the house that Jack built."
        ]
        self.assertEqual(recite(5, 5), expected)

    def test_verse_six(self):
        expected = [
            "This is the cow with the crumpled horn"
            "that tossed the dog"
            "that worried the cat"
            "that killed the rat"
            "that ate the malt"
            "that lay in the house that Jack built."
        ]
        self.assertEqual(recite(6, 6), expected)

    def test_verse_seven(self):
        expected = [
            "This is the maiden all forlorn"
            "that milked the cow with the crumpled horn"
            "that tossed the dog"
            "that worried the cat"
            "that killed the rat"
            "that ate the malt"
            "that lay in the house that Jack built."
        ]
        self.assertEqual(recite(7, 7), expected)

    def test_verse_eight(self):
        expected = [
            "This is the man all tattered and torn"
            "that kissed the maiden all forlorn"
            "that milked the cow with the crumpled horn"
            "that tossed the dog"
            "that worried the cat"
            "that killed the rat"
            "that ate the malt"
            "that lay in the house that Jack built."
        ]
        self.assertEqual(recite(8, 8), expected)

    def test_verse_nine(self):
        expected = [
            "This is the priest all shaven and shorn"
            "that married the man all tattered and torn"
            "that kissed the maiden all forlorn"
            "that milked the cow with the crumpled horn"
            "that tossed the dog"
            "that worried the cat"
            "that killed the rat"
            "that ate the malt"
            "that lay in the house that Jack built."
        ]
        self.assertEqual(recite(9, 9), expected)

    def test_verse_10(self):
        expected = [
            "This is the rooster that crowed in the morn"
            "that woke the priest all shaven and shorn"
            "that married the man all tattered and torn"
            "that kissed the maiden all forlorn"
            "that milked the cow with the crumpled horn"
            "that tossed the dog"
            "that worried the cat"
            "that killed the rat"
            "that ate the malt"
            "that lay in the house that Jack built."
        ]
        self.assertEqual(recite(10, 10), expected)

    def test_verse_11(self):
        expected = [
            "This is the farmer sowing his corn"
            "that kept the rooster that crowed in the morn"
            "that woke the priest all shaven and shorn"
            "that married the man all tattered and torn"
            "that kissed the maiden all forlorn"
            "that milked the cow with the crumpled horn"
            "that tossed the dog"
            "that worried the cat"
            "that killed the rat"
            "that ate the malt"
            "that lay in the house that Jack built."
        ]
        self.assertEqual(recite(11, 11), expected)

    def test_verse_12(self):
        expected = [
            "This is the horse and the hound and the horn"
            "that belonged to the farmer sowing his corn"
            "that kept the rooster that crowed in the morn"
            "that woke the priest all shaven and shorn"
            "that married the man all tattered and torn"
            "that kissed the maiden all forlorn"
            "that milked the cow with the crumpled horn"
            "that tossed the dog"
            "that worried the cat"
            "that killed the rat"
            "that ate the malt"
            "that lay in the house that Jack built."
        ]
        self.assertEqual(recite(12, 12), expected)

    def test_multiple_verses(self):
        expected = [recite(i, i)[0] for i in range(4, 9)]
        self.assertEqual(recite(4, 8), expected)

    def test_full_rhyme(self):
        expected = [recite(i, i)[0] for i in range(1, 13)]
        self.assertEqual(recite(1, 12), expected)


if __name__ == '__main__':
    unittest.main()
class House:

    LYRICS = [("built", "house that Jack"),
              ("ate", "malt"),
              ("killed", "rat"),
              ("worried", "cat"),
              ("tossed", "dog"),
              ("milked", "cow with the crumpled horn"),
              ("kissed", "maiden all forlorn"),
              ("married", "man all tattered and torn"),
              ("woke", "priest all shaven and shorn"),
              ("kept", "rooster that crowed in the morn"),
              ("belonged to", "farmer sowing his corn"),
              ("", "horse and the hound and the horn")]

    LAST_LINE = "that lay in the house that Jack built."

    @classmethod
    def rhyme(cls):
        return "\n\n".join([cls.verse(i) for i in range(12)])

    @classmethod
    def verse(cls, verse_num):
        return "\n".join(filter(None, cls.parts(verse_num)))

    @classmethod
    def parts(cls, verse_num):
        return [cls.first(verse_num), cls.middle(verse_num),
                cls.last(verse_num)]

    @classmethod
    def first(cls, verse_num):
        if verse_num != 0:
            return cls.first_partial(verse_num)
        return cls.first_partial(verse_num) + " " + cls.verb(verse_num) + "."

    @classmethod
    def first_partial(cls, verse_num):
        return "This is the " + cls.noun(verse_num)

    @classmethod
    def middle(cls, verse_num):
        if verse_num >= 2:
            return "\n".join([cls.middle_partial(num) for num in
                              range(verse_num - 1, 0, -1)])

    @classmethod
    def middle_partial(cls, num):
        return "that " + cls.verb(num) + " the " + cls.noun(num)

    @classmethod
    def verb(cls, num):
        return cls.LYRICS[num][0]

    @classmethod
    def noun(cls, num):
        return cls.LYRICS[num][1]

    @classmethod
    def last(cls, verse_num):
        if verse_num != 0:
            return cls.LAST_LINE


def verse(verse_num):
    return House.verse(verse_num)


def rhyme():
    return House.rhyme()

Community comments

Find this solution interesting? Ask the author a question to learn more.
Avatar of deleted-user-161253
deleted-user-161253
commented about 5 years ago

Why do you use a class when do then declare every single method static?

What can you learn from this solution?

A huge amount can be learned from reading other peopleโ€™s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that you could read more about to improve your understanding?