Added python dict interface

Author: calebmadrigal

hashtable.py

@@ -5,13 +5,22 @@ def hash_function(key_str, size):
 
 ############ HashTable class
 class HashTable:
-    """ Hash table which uses strings for keys. Value can be any object. """
+    """ Hash table which uses strings for keys. Value can be any object.
+
+    Example usage:
+
+        ht = HashTable(10)
+        ht.set('a', 1).set('b', 2).set('c', 3)
+        ht['c'] = 30
+
+    """
 
     def __init__(self, capacity=1000):
         """ Capacity defaults to 1000. """
 
         self.capacity = capacity
         self.size = 0
+        self._keys = []
         # Storage format: [ [ [key1, value], [key2, value] ], [ [key3, value] ] ]
         # The outmost list is the one which the hash function maps the index to. The next inner
         # Array is the list of objects in that storage cell. The 3rd level is the individual
@@ -39,6 +48,7 @@ def find_result_func(found_item, hash_table_cell):
             else:
                 hash_table_cell.append([key, obj])
                 self.size += 1
+                self._keys.append(key)
 
         self._find_by_key(key, find_result_func)
         return self
@@ -61,14 +71,33 @@ def remove(self, key):
         def find_result_func(found_item, hash_table_cell):
             if found_item:
                 hash_table_cell.remove(found_item)
+                self._keys.remove(key)
                 self.size -= 1
                 return found_item[1]
             else:
                 raise KeyError(key)
 
         return self._find_by_key(key, find_result_func)
 
+    ####### Python's dict interface
+
+    def keys(self):
+        return self._keys
+
+    def __setitem__(self, key, value):
+        self.set(key, value)
+
+    def __getitem__(self, key):
+        return self.get(key)
+
+    def __delitem__(self, key):
+        return self.remove(key)
+
+    def __repr__(self):
+        return '{ ' + ', '.join([key + ':' + str(self.get(key)) for key in self._keys]) + ' }'
+
 if __name__ == "__main__":
+    # Run unit tests
     import unittest
     testsuite = unittest.TestLoader().discover('test', pattern="*hashtable*")
     unittest.TextTestRunner(verbosity=1).run(testsuite)

test/test_hashtable.py

@@ -71,6 +71,20 @@ def testRemove(self):
         self.assertEqual(removed_item, 1)
         self.assertEqual(ht.size, 0)
 
+    def testPythonDictInterface(self):
+        ht = hashtable.HashTable(10)
+
+        ht['a'] = 10
+        self.assertEqual(ht.get('a'), 10)
+
+        ht['a'] = 20
+        self.assertEqual(ht['a'], 20)
+
+        self.assertIn('a', ht.keys())
+
+        del ht['a']
+        self.assertRaises(KeyError, ht.get, 'a')
+
 if __name__ == '__main__':
     unittest.main()