Give a slightly more clear error on bad array sizes

nilmdb/client/numpyclient.py

@@ -162,9 +162,12 @@ class StreamInserterNumpy(nilmdb.client.client.StreamInserter):
         elif array.ndim == 2:
             # Convert to structured array
             sarray = numpy.zeros(array.shape[0], dtype=self._dtype)
-            sarray['timestamp'] = array[:,0]
-            # Need the squeeze in case sarray['data'] is 1 dimensional
-            sarray['data'] = numpy.squeeze(array[:,1:])
+            try:
+                sarray['timestamp'] = array[:,0]
+                # Need the squeeze in case sarray['data'] is 1 dimensional
+                sarray['data'] = numpy.squeeze(array[:,1:])
+            except (IndexError, ValueError):
+                raise ValueError("wrong number of fields for this data type")
             array = sarray
         else:
             raise ValueError("wrong number of dimensions in array")