Fix slow object arrays indexing (#1122)

* fixing #1121

* added changelog

Author: burnpanck

doc/whats-new.rst

@@ -134,6 +134,9 @@ Bug fixes
   (:issue:`1116`).
   By `Yves Delley <https://github.com/burnpanck>`_.
 
+- Fixed sub-optimal performance in certain operations with object arrays (:issue:`1121`).
+  By `Yves Delley <https://github.com/burnpanck>`_.
+
 .. _whats-new.0.8.2:
 
 v0.8.2 (18 August 2016)

xarray/core/utils.py

@@ -197,9 +197,8 @@ def is_valid_numpy_dtype(dtype):
 
 def to_0d_object_array(value):
     """Given a value, wrap it in a 0-D numpy.ndarray with dtype=object."""
-    result = np.empty((1,), dtype=object)
-    result[:] = [value]
-    result.shape = ()
+    result = np.empty((), dtype=object)
+    result[()] = value
     return result