MAINT: FutureWarning for changes to np.average subclass handling

Fixes #7403

1 files changed, 13 insertions, 1 deletions

diff --git a/numpy/lib/function_base.py b/numpy/lib/function_base.py
index 93f4f2634..6d06eb4f5 100644
--- a/numpy/lib/function_base.py
+++ b/numpy/lib/function_base.py
@@ -1002,7 +1002,19 @@ def average(a, axis=None, weights=None, returned=False):
     TypeError: Axis must be specified when shapes of a and weights differ.
 
     """
-    a = np.asanyarray(a)
+    # 3/19/2016 1.12.0:
+    # replace the next few lines with "a = np.asanyarray(a)"
+    if (type(a) not in (np.ndarray, np.matrix) and
+            issubclass(type(a), np.ndarray)):
+        warnings.warn("np.average currently does not preserve subclasses, but "
+                      "will do so in the future to match the behavior of most "
+                      "other numpy functions such as np.mean. In particular, "
+                      "this means calls which returned a scalar may return a "
+                      "0-d subclass object instead.",
+                      FutureWarning, stacklevel=2)
+
+    if not isinstance(a, np.matrix):
+        a = np.asarray(a)
 
     if weights is None:
         avg = a.mean(axis)