Fix ndindex for 0-d arrays.

numpy/lib/index_tricks.py

@@ -502,7 +502,6 @@ def next(self):
     def __iter__(self):
         return self
 
-
 class ndindex(object):
     """
     An N-dimensional iterator object to index arrays.
@@ -535,6 +534,9 @@ class ndindex(object):
     def __init__(self, *shape):
         x = as_strided(_nx.zeros(1), shape=shape, strides=_nx.zeros_like(shape))
         self._it = _nx.nditer(x, flags=['multi_index'], order='C')
+        # This is a patch to handle 0-d arrays correctly on the Python side.
+        # We might want to revisit nditer in the future to handle this         
+        self._zerod = (len(shape)==0)
 
     def __iter__(self):
         return self
@@ -558,6 +560,13 @@ def next(self):
 
         """
         self._it.next()
+        # This is a hack with an un-necessary check in every next call
+        # But, it's much simpler than writing another iterator for 0-d arrays
+        #  because the Python iterator protocol does not respect monkey-patching
+        #  the next method on an instance.
+        # Given that we should fix nditer eventually, we do this for now.
+        if self._zerod:
+            return ()
         return self._it.multi_index