Fix extended slicing on RedisList

pottery/__init__.py

@@ -18,7 +18,7 @@
 
 
 __title__ = 'pottery'
-__version__ = '1.1.3'
+__version__ = '1.1.4'
 __description__, __long_description__ = (
     s.strip() for s in __doc__.split(sep='\n\n', maxsplit=1)
 )

pottery/list.py

@@ -86,11 +86,15 @@ def __getitem__(self, index: Union[slice, int]) -> Any:
             # our ridiculous hack is to get all of the elements between
             # start and stop from Redis, then discard the ones between step
             # in Python.  More info:
-            # http://redis.io/commands/lrange
+            #   http://redis.io/commands/lrange
             with self._watch() as pipeline:
                 indices = self.__slice_to_indices(index)
+                if indices.step >= 0:
+                    start, stop = indices.start, indices.stop-1
+                else:
+                    start, stop = indices.stop+1, indices.start
                 pipeline.multi()
-                pipeline.lrange(self.key, indices[0], indices[-1])
+                pipeline.lrange(self.key, start, stop)
                 encoded = pipeline.execute()[0]
                 encoded = encoded[::index.step]
                 value: Union[List[JSONTypes], JSONTypes] = [self._decode(value) for value in encoded]

tests/test_list.py

@@ -54,7 +54,7 @@ def test_mutability_and_append(self):
         cubes.append(7**3)
         assert cubes == [1, 8, 27, 64, 125, 216, 343]
 
-    def test_slices(self):
+    def test_slicing(self):
         letters = RedisList(
             ('a', 'b', 'c', 'd', 'e', 'f', 'g'),
             redis=self.redis,
@@ -216,3 +216,28 @@ def test_json_dumps(self):
             '["foo", "bar", "baz", "qux", "quux", "corge", "grault", "garply", '
             '"waldo", "fred", "plugh", "xyzzy", "thud"]'
         )
+
+    def test_extended_slicing(self):
+        python_list = [1, 2, 3, 4, 5]
+        redis_list = RedisList(python_list, redis=self.redis)
+        assert redis_list[len(redis_list)-1:3-1:-1] == python_list[len(python_list)-1:3-1:-1]
+
+    def test_slice_notation(self):
+        # I got these examples from:
+        #   https://railsware.com/blog/python-for-machine-learning-indexing-and-slicing-for-lists-tuples-strings-and-other-sequential-types/#Slice_Notation
+        nums = RedisList((10, 20, 30, 40, 50, 60, 70, 80, 90), redis=self.redis)
+        assert nums[2:7] == [30, 40, 50, 60, 70]
+        assert nums[0:4] == [10, 20, 30, 40]
+        assert nums[:5] == [10, 20, 30, 40, 50]
+        assert nums[-3:] == [70, 80, 90]
+        assert nums[1:-1] == [20, 30, 40, 50, 60, 70, 80]
+        assert nums[-3:8] == [70, 80]
+        assert nums[-5:-1] == [50, 60, 70, 80]
+        assert nums[:-2] == [10, 20, 30, 40, 50, 60, 70]
+        assert nums[::2] == [10, 30, 50, 70, 90]
+        assert nums[1::2] == [20, 40, 60, 80]
+        assert nums[1:-3:2] == [20, 40, 60]
+        assert nums[::-1] == [90, 80, 70, 60, 50, 40, 30, 20, 10]
+        assert nums[-2::-1] == [80, 70, 60, 50, 40, 30, 20, 10]
+        assert nums[-2:1:-1] == [80, 70, 60, 50, 40, 30]
+        assert nums[-2:1:-3] == [80, 50]