Merge branch 'ddb2-port-lookup' into develop

Fixes #1780.

boto/dynamodb2/table.py

@@ -418,6 +418,45 @@ def get_item(self, consistent=False, **kwargs):
         item.load(item_data)
         return item
 
+    def lookup(self, *args, **kwargs):
+        """
+        Look up an entry in DynamoDB. This is mostly backwards compatible
+        with boto.dynamodb. Unlike get_item, it takes hash_key and range_key first,
+        although you may still specify keyword arguments instead.
+
+        Also unlike the get_item command, if the returned item has no keys 
+        (i.e., it does not exist in DynamoDB), a None result is returned, instead
+        of an empty key object.
+
+        Example::
+            >>> user = users.lookup(username)
+            >>> user = users.lookup(username, consistent=True)
+            >>> app = apps.lookup('my_customer_id', 'my_app_id')
+
+        """
+        if not self.schema:
+            self.describe()
+        for x, arg in enumerate(args):
+            kwargs[self.schema[x].name] = arg
+        ret = self.get_item(**kwargs)
+        if not ret.keys():
+            return None
+        return ret
+
+    def new_item(self, *args):
+        """
+        Returns a new, blank item
+
+        This is mostly for consistency with boto.dynamodb
+        """
+        if not self.schema:
+            self.describe()
+        data = {}
+        for x, arg in enumerate(args):
+            data[self.schema[x].name] = arg
+        return Item(self, data=data)
+
+
     def put_item(self, data, overwrite=False):
         """
         Saves an entire item to DynamoDB.
@@ -1164,4 +1203,4 @@ def resend_unprocessed(self):
             self.handle_unprocessed(resp)
             boto.log.info(
                 "%s unprocessed items left" % len(self._unprocessed)
-            )
+            )

tests/unit/dynamodb2/test_table.py

@@ -1286,6 +1286,64 @@ def test_get_item(self):
             'username': {'S': 'johndoe'}
         }, consistent_read=False)
 
+    def test_lookup_hash(self):
+        """Tests the "lookup" function with just a hash key"""
+        expected = {
+            'Item': {
+                'username': {'S': 'johndoe'},
+                'first_name': {'S': 'John'},
+                'last_name': {'S': 'Doe'},
+                'date_joined': {'N': '1366056668'},
+                'friend_count': {'N': '3'},
+                'friends': {'SS': ['alice', 'bob', 'jane']},
+            }
+        }
+
+        # Set the Schema
+        self.users.schema = [
+            HashKey('username'),
+            RangeKey('date_joined', data_type=NUMBER),
+        ]
+
+        with mock.patch.object(
+                self.users,
+                'get_item',
+                return_value=expected) as mock_get_item:
+            self.users.lookup('johndoe')
+
+        mock_get_item.assert_called_once_with(
+            username= 'johndoe')
+
+    def test_lookup_hash_and_range(self):
+        """Test the "lookup" function with a hash and range key"""
+        expected = {
+            'Item': {
+                'username': {'S': 'johndoe'},
+                'first_name': {'S': 'John'},
+                'last_name': {'S': 'Doe'},
+                'date_joined': {'N': '1366056668'},
+                'friend_count': {'N': '3'},
+                'friends': {'SS': ['alice', 'bob', 'jane']},
+            }
+        }
+
+        # Set the Schema
+        self.users.schema = [
+            HashKey('username'),
+            RangeKey('date_joined', data_type=NUMBER),
+        ]
+
+        with mock.patch.object(
+                self.users,
+                'get_item',
+                return_value=expected) as mock_get_item:
+            self.users.lookup('johndoe', 1366056668)
+
+        mock_get_item.assert_called_once_with(
+            username= 'johndoe',
+            date_joined= 1366056668)
+
+
     def test_put_item(self):
         with mock.patch.object(
                 self.users.connection,