MNT: always validate alpha as [0, 1] or None

matplotlib · jenshnielsen · Mar 29, 2016 · Dec 31, 2015 · Jan 2, 2016 · Jan 2, 2016
commit bda202b78eef4374f69bda9d011313645ec206ce
diff --git a/lib/matplotlib/colors.py b/lib/matplotlib/colors.py
@@ -203,6 +203,9 @@ def to_rgba(self, arg, alpha=None):
        except AttributeError:
            pass

+        if alpha is not None and (alpha < 0.0 or alpha > 1.0):
+            raise ValueError("alpha must be in range 0-1")
+
        try:
            if not cbook.is_string_like(arg) and cbook.iterable(arg):
                if len(arg) == 4:
@@ -211,8 +214,6 @@ def to_rgba(self, arg, alpha=None):
                            'number in rbga sequence outside 0-1 range')
                    if alpha is None:
                        return tuple(arg)
-                    if alpha < 0.0 or alpha > 1.0:
-                        raise ValueError("alpha must be in range 0-1")
                    return arg[0], arg[1], arg[2], alpha
                if len(arg) == 3:
                    r, g, b = arg