[formatter] allow for numeric list and string indices

gallery_dl/util.py

@@ -512,16 +512,19 @@ class Formatter():
         for is_attr, key in rest:
             if is_attr:
                 func = operator.attrgetter
-            elif ":" in key:
-                func = operator.itemgetter
-                start, _, stop = key.partition(":")
-                stop, _, step = stop.partition(":")
-                start = int(start) if start else None
-                stop = int(stop) if stop else None
-                step = int(step) if step else None
-                key = slice(start, stop, step)
             else:
                 func = operator.itemgetter
+                try:
+                    if ":" in key:
+                        start, _, stop = key.partition(":")
+                        stop, _, step = stop.partition(":")
+                        start = int(start) if start else None
+                        stop = int(stop) if stop else None
+                        step = int(step) if step else None
+                        key = slice(start, stop, step)
+                except TypeError:
+                    pass  # key is an integer
+
             funcs.append(func(key))
 
         return first, funcs

test/test_util.py

@@ -340,6 +340,10 @@ class TestFormatter(unittest.TestCase):
         self._run_test("{d[a]|d[b]|d[c]}", "foo")
         self._run_test("{d[z]|d[y]|d[x]}", "None")
 
+    def test_indexing(self):
+        self._run_test("{l[0]}" , "a")
+        self._run_test("{a[6]}" , "w")
+
     def test_slicing(self):
         v = self.kwdict["a"]
         self._run_test("{a[1:10]}"  , v[1:10])