API : Only allow addition of equal length cycles

tacaswell · tacaswell · commit a56ea63d1bec · 2015-05-05T23:37:14.000-04:00
Now that we have both multiplication and slicing, it is easy
to get correct length cyclers to add together
diff --git a/lib/matplotlib/cycler.py b/lib/matplotlib/cycler.py
@@ -110,6 +110,9 @@ def __iter__(self):
         return self._compose()
 
     def __add__(self, other):
+        if len(self) != len(other):
+            raise ValueError("Can only add equal length cycles, "
+                             "not {0} and {1}".format(len(self), len(other)))
         return Cycler(self, other, zip)
 
     def __mul__(self, other):
diff --git a/lib/matplotlib/tests/test_cycler.py b/lib/matplotlib/tests/test_cycler.py
@@ -39,9 +39,8 @@ def test_compose():
     yield _cycler_helper, c2+c1, 3, ['c', 'lw'], [list('rgb'), range(3)]
     yield _cycles_equal, c2+c1, c1+c2
     # miss-matched add lengths
-    yield _cycler_helper, c1+c3, 3, ['c', 'lw'], [list('rgb'), range(3)]
-    yield _cycler_helper, c3+c1, 3, ['c', 'lw'], [list('rgb'), range(3)]
-    yield _cycles_equal, c3+c1, c1+c3
+    assert_raises(ValueError, add, c1, c3)
+    assert_raises(ValueError, add, c3, c1)
 
     # multiplication
     target = zip(*product(list('rgb'), range(3)))
