Address comments and some code simplifications

Author: WeatherGod

cycler.py

@@ -138,7 +138,7 @@ def keys(self):
         """
         return set(self._keys)
 
-    def key_change(self, old, new):
+    def change_key(self, old, new):
         """
         Change a key in this cycler to a new name.
         Modification is performed in-place.
@@ -161,20 +161,17 @@ def key_change(self, old, new):
         self._keys.add(new)
 
         if self._right is not None and old in self._right.keys:
-            self._right.key_change(old, new)
-        elif self._left is not None:
-            if isinstance(self._left, Cycler):
-                self._left.key_change(old, new)
-            else:
-                Cycler._key_change(iter(self._left), old, new)
-
-    @staticmethod
-    def _key_change(itr, old, new):
-        entry = six.next(itr)
-        if old in entry:
-            entry[new] = entry[old]
-            del entry[old]
-            for entry in itr:
+            self._right.change_key(old, new)
+
+        # self._left should always be non-None
+        # if self._keys is non-empty.
+        elif isinstance(self._left, Cycler):
+            self._left.change_key(old, new)
+        else:
+            # It should be completely safe at this point to
+            # assume that the old key can be found in each
+            # iteration.
+            for entry in self._left:
                 entry[new] = entry[old]
                 del entry[old]
 

test_cycler.py

@@ -221,25 +221,25 @@ def test_keychange():
     c2 = cycler('lw', [1, 2, 3])
     c3 = cycler('ec', 'yk')
 
-    c3.key_change('ec', 'edgecolor')
+    c3.change_key('ec', 'edgecolor')
     assert_equal(c3, cycler('edgecolor', c3))
 
     c = c1 + c2
-    c.key_change('lw', 'linewidth')
+    c.change_key('lw', 'linewidth')
     assert_equal(c, c1 + cycler('linewidth', c2))
 
     c = (c1 + c2) * c3
-    c.key_change('c', 'color')
+    c.change_key('c', 'color')
     assert_equal(c, (cycler('color', c1) + c2) * c3)
 
     # Perfectly fine, it is a no-op
-    c.key_change('color', 'color')
+    c.change_key('color', 'color')
     assert_equal(c, (cycler('color', c1) + c2) * c3)
 
     # Can't change a key to one that is already in there
-    assert_raises(ValueError, Cycler.key_change, c, 'color', 'linewidth')
+    assert_raises(ValueError, Cycler.change_key, c, 'color', 'linewidth')
     # Can't change a key you don't have
-    assert_raises(KeyError, Cycler.key_change, c, 'c', 'foobar')
+    assert_raises(KeyError, Cycler.change_key, c, 'c', 'foobar')
 
 
 def _eq_test_helper(a, b, res):