custom-set: implement exercise

config.json

@@ -1234,6 +1234,16 @@
         "object_oriented_programming"
       ]
     },
+    {
+        "uuid": "bb07c236-062c-2980-483a-a221e4724445dcd6f32",
+        "slug": "custom-set",
+        "core": false,
+        "unlocked_by": null,
+        "difficulty": 5,
+        "topics": [
+            "sets"
+        ]
+    },
     {
       "uuid": "e7351e8e-d3ff-4621-b818-cd55cf05bffd",
       "slug": "accumulate",

exercises/custom-set/README.md

@@ -0,0 +1,20 @@
+# Custom-Set
+
+Create a custom set type.
+
+Sometimes it is necessary to define a custom data structure of some
+type, like a set. In this exercise you will define your own set. How it
+works internally doesn't matter, as long as it behaves like a set of
+unique elements.
+
+## Submitting Exercises
+
+Note that, when trying to submit an exercise, make sure the solution is in the `exercism/python/<exerciseName>` directory.
+
+For example, if you're submitting `bob.py` for the Bob exercise, the submit command would be something like `exercism submit <path_to_exercism_dir>/python/bob/bob.py`.
+
+For more detailed information about running tests, code style and linting,
+please see the [help page](http://exercism.io/languages/python).
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

exercises/custom-set/custom_set.py

@@ -0,0 +1,30 @@
+class CustomSet(object):
+    def __init__(self, elements=[]):
+        pass
+
+    def empty(self):
+        pass
+
+    def __iter__(self):
+        pass
+
+    def subset(self, other):
+        pass
+
+    def disjoint(self, other):
+        pass
+
+    def __eq__(self, other):
+        pass
+
+    def add(self, element):
+        pass
+
+    def intersection(self, other):
+        pass
+
+    def difference(self, other):
+        pass
+
+    def union(self, other):
+        pass

exercises/custom-set/custom_set_test.py

@@ -0,0 +1,212 @@
+import unittest
+
+from custom_set import CustomSet
+
+
+# Tests adapted from `problem-specifications//canonical-data.json` @ v1.1.0
+
+class CustomSetTest(unittest.TestCase):
+    def test_sets_with_no_elements_are_empty(self):
+        sut = CustomSet()
+        self.assertIs(sut.empty(), True)
+
+    def test_sets_with_elements_are_not_empty(self):
+        sut = CustomSet([1])
+        self.assertIs(sut.empty(), False)
+
+    def test_empty_set_contains_nothing(self):
+        sut = CustomSet()
+        self.assertNotIn(1, sut)
+
+    def test_set_contains_when_element_in_set(self):
+        sut = CustomSet([1])
+        self.assertIn(1, sut)
+
+    def test_set_does_not_contains_when_element_not_in_set(self):
+        sut = CustomSet([1, 2, 3])
+        self.assertNotIn(4, sut)
+
+    def test_empty_set_is_subset_of_another_empty_set(self):
+        set1 = CustomSet()
+        set2 = CustomSet()
+        self.assertIs(set1.subset(set2), True)
+
+    def test_empty_set_is_subset_of_non_empty_set(self):
+        set1 = CustomSet()
+        set2 = CustomSet([1])
+        self.assertIs(set1.subset(set2), True)
+
+    def test_non_empty_set_is_not_subet_of_empty_set(self):
+        set1 = CustomSet([1])
+        set2 = CustomSet()
+        self.assertIs(set1.subset(set2), False)
+
+    def test_set_is_subset_of_set_with_exact_same_elements(self):
+        set1 = CustomSet([1, 2, 3])
+        set2 = CustomSet([1, 2, 3])
+        self.assertIs(set1.subset(set2), True)
+
+    def test_set_is_subset_of_larger_set_with_same_elements(self):
+        set1 = CustomSet([1, 2, 3])
+        set2 = CustomSet([4, 1, 2, 3])
+        self.assertIs(set1.subset(set2), True)
+
+    def test_set_not_subset_of_set_that_does_not_contain_its_elements(self):
+        set1 = CustomSet([1, 2, 3])
+        set2 = CustomSet([4, 1, 3])
+        self.assertIs(set1.subset(set2), False)
+
+    def test_empty_set_disjoint_with_itself(self):
+        set1 = CustomSet()
+        set2 = CustomSet()
+        self.assertIs(set1.disjoint(set2), True)
+
+    def test_empty_set_disjoint_with_non_empty_set(self):
+        set1 = CustomSet()
+        set2 = CustomSet([1])
+        self.assertIs(set1.disjoint(set2), True)
+
+    def test_non_empty_set_disjoint_with_empty_set(self):
+        set1 = CustomSet([1])
+        set2 = CustomSet()
+        self.assertIs(set1.disjoint(set2), True)
+
+    def test_sets_not_disjoint_if_element_is_shared(self):
+        set1 = CustomSet([1, 2])
+        set2 = CustomSet([2, 3])
+        self.assertIs(set1.disjoint(set2), False)
+
+    def test_sets_disjoint_if_not_elements_are_shared(self):
+        set1 = CustomSet([1, 2])
+        set2 = CustomSet([3, 4])
+        self.assertIs(set1.disjoint(set2), True)
+
+    def test_empty_sets_are_equal(self):
+        set1 = CustomSet()
+        set2 = CustomSet()
+        self.assertEqual(set1, set2)
+
+    def test_empty_set_not_equal_to_non_empty_set(self):
+        set1 = CustomSet()
+        set2 = CustomSet([1, 2, 3])
+        self.assertNotEqual(set1, set2)
+
+    def test_non_empty_set_not_equal_to_empty_set(self):
+        set1 = CustomSet([1, 2, 3])
+        set2 = CustomSet()
+        self.assertNotEqual(set1, set2)
+
+    def test_sets_with_same_exact_same_elements_are_equal(self):
+        set1 = CustomSet([1, 2])
+        set2 = CustomSet([2, 1])
+        self.assertEqual(set1, set2)
+
+    def test_sets_with_different_elements_are_not_equal(self):
+        set1 = CustomSet([1, 2, 3])
+        set2 = CustomSet([1, 2, 4])
+        self.assertNotEqual(set1, set2)
+
+    def test_set_is_not_equal_to_larger_set_with_same_elements(self):
+        set1 = CustomSet([1, 2, 3])
+        set2 = CustomSet([1, 2, 3, 4])
+        self.assertNotEqual(set1, set2)
+
+    def test_add_to_empty_set(self):
+        sut = CustomSet()
+        sut.add(1)
+        expected = CustomSet([1])
+        self.assertEqual(sut, expected)
+
+    def test_add_to_non_empty_set(self):
+        sut = CustomSet([1, 2, 4])
+        sut.add(3)
+        expected = CustomSet([1, 2, 3, 4])
+        self.assertEqual(sut, expected)
+
+    def test_adding_existing_element_does_not_change_set(self):
+        sut = CustomSet([1, 2, 3])
+        sut.add(3)
+        expected = CustomSet([1, 2, 3])
+        self.assertEqual(sut, expected)
+
+    def test_intersection_of_two_empty_sets_is_empty_set(self):
+        set1 = CustomSet()
+        set2 = CustomSet()
+        expected = CustomSet()
+        self.assertEqual(set1.intersection(set2), expected)
+
+    def test_intersection_of_empty_set_and_non_empty_set_is_empty_set(self):
+        set1 = CustomSet()
+        set2 = CustomSet([3, 2, 5])
+        expected = CustomSet()
+        self.assertEqual(set1.intersection(set2), expected)
+
+    def test_intersection_of_non_empty_set_and_empty_set_is_empty_set(self):
+        set1 = CustomSet([1, 2, 3, 4])
+        set2 = CustomSet()
+        expected = CustomSet()
+        self.assertEqual(set1.intersection(set2), expected)
+
+    def test_intersection_of_sets_with_no_shared_elements_is_empty_set(self):
+        set1 = CustomSet([1, 2, 3])
+        set2 = CustomSet([4, 5, 6])
+        expected = CustomSet()
+        self.assertEqual(set1.intersection(set2), expected)
+
+    def test_intersection_contains_shared_elements_only(self):
+        set1 = CustomSet([1, 2, 3, 4])
+        set2 = CustomSet([3, 2, 5])
+        expected = CustomSet([2, 3])
+        self.assertEqual(set1.intersection(set2), expected)
+
+    def test_difference_of_two_empty_sets_is_empty_set(self):
+        set1 = CustomSet()
+        set2 = CustomSet()
+        expected = CustomSet()
+        self.assertEqual(set1 - set2, expected)
+
+    def test_difference_of_empty_set_and_non_empty_set_is_empty_set(self):
+        set1 = CustomSet()
+        set2 = CustomSet([3, 2, 5])
+        expected = CustomSet()
+        self.assertEqual(set1 - set2, expected)
+
+    def test_difference_of_non_empty_set_and_empty_set_is_non_empty_set(self):
+        set1 = CustomSet([1, 2, 3, 4])
+        set2 = CustomSet()
+        expected = CustomSet([1, 2, 3, 4])
+        self.assertEqual(set1 - set2, expected)
+
+    def test_difference_of_non_empty_sets_elements_in_first_set_only(self):
+        set1 = CustomSet([3, 2, 1])
+        set2 = CustomSet([2, 4])
+        expected = CustomSet([1, 3])
+        self.assertEqual(set1 - set2, expected)
+
+    def test_union_of_empty_sets_is_empty_set(self):
+        set1 = CustomSet()
+        set2 = CustomSet()
+        expected = CustomSet()
+        self.assertEqual(set1 + set2, expected)
+
+    def test_union_of_empty_set_and_non_empty_set_is_the_non_empty_set(self):
+        set1 = CustomSet()
+        set2 = CustomSet([2])
+        expected = CustomSet([2])
+        self.assertEqual(set1 + set2, expected)
+
+    def test_union_of_non_empty_set_and_empty_set_is_the_non_empty_set(self):
+        set1 = CustomSet([1, 3])
+        set2 = CustomSet()
+        expected = CustomSet([1, 3])
+        self.assertEqual(set1 + set2, expected)
+
+    def test_union_of_non_empty_sets_contains_all_unique_elements(self):
+        set1 = CustomSet([1, 3])
+        set2 = CustomSet([2, 3])
+        expected = CustomSet([1, 2, 3])
+        self.assertEqual(set1 + set2, expected)
+
+
+if __name__ == '__main__':
+    unittest.main()

exercises/custom-set/example.py

@@ -0,0 +1,42 @@
+class CustomSet(object):
+    def __init__(self, elements=[]):
+        self.elements = list(elements)
+
+    def empty(self):
+        return not any(self.elements)
+
+    def __iter__(self):
+        return iter(self.elements)
+
+    def subset(self, other):
+        return all(x in other for x in self)
+
+    def disjoint(self, other):
+        return all(x not in other for x in self)
+
+    def __eq__(self, other):
+        return self.subset(other) and other.subset(self)
+
+    def add(self, element):
+        if element not in self:
+            self.elements.append(element)
+
+    def intersection(self, other):
+        result = CustomSet()
+        for x in self:
+            if x in other:
+                result.add(x)
+        return result
+
+    def __sub__(self, other):
+        result = CustomSet()
+        for x in self:
+            if x not in other:
+                result.add(x)
+        return result
+
+    def __add__(self, other):
+        result = CustomSet(self.elements)
+        for x in other:
+            result.add(x)
+        return result