isogram: Add new exercise (#424)

Author: behrtam

config.json

@@ -33,6 +33,12 @@
           "text formatting"
       ]
     },
+    {
+      "slug": "isogram",
+      "difficulty": 1,
+      "topics": [
+      ]
+    },
     {
       "slug": "pangram",
       "difficulty": 1,

exercises/isogram/example.py

@@ -0,0 +1,3 @@
+def is_isogram(string):
+    characters_lower = [c.lower() for c in string if c.isalpha()]
+    return len(set(characters_lower)) == len(characters_lower)

exercises/isogram/isogram.py

@@ -0,0 +1,2 @@
+def is_isogram():
+    pass

exercises/isogram/isogram_test.py

@@ -0,0 +1,35 @@
+import unittest
+from isogram import is_isogram
+
+
+# test cases adapted from `x-common//canonical-data.json` @ version: 1.0.0
+
+class TestIsogram(unittest.TestCase):
+
+    def test_empty_string(self):
+        self.assertTrue(is_isogram(""))
+
+    def test_isogram_with_only_lower_case_characters(self):
+        self.assertTrue(is_isogram("isogram"))
+
+    def test_word_with_one_duplicated_character(self):
+        self.assertFalse(is_isogram("eleven"))
+
+    def test_longest_reported_english_isogram(self):
+        self.assertTrue(is_isogram("subdermatoglyphic"))
+
+    def test_word_with_duplicated_character_in_mixed_case(self):
+        self.assertFalse(is_isogram("Alphabet"))
+
+    def test_hypothetical_isogrammic_word_with_hyphen(self):
+        self.assertTrue(is_isogram("thumbscrew-japingly"))
+
+    def test_isogram_with_duplicated_non_letter_character(self):
+        self.assertTrue(is_isogram("Hjelmqvist-Gryb-Zock-Pfund-Wax"))
+
+    def test_made_up_name_that_is_an_isogram(self):
+        self.assertTrue(is_isogram("Emily Jung Schwartzkopf"))
+
+
+if __name__ == '__main__':
+    unittest.main()