moar fixes

Author: jreback

pandas/core/internals.py

@@ -855,6 +855,23 @@ def putmask(self, mask, new, align=True, inplace=False, axis=0,
                         new, new_values.shape[-1]).reshape(self.shape)
                 new = new.astype(new_values.dtype)
 
+            # we require exact matches between the len of the
+            # values we are setting (or is compat). np.putmask
+            # doesn't check this and will simply truncate / pad
+            # the output, but we want sane error messages
+            #
+            # TODO: this prob needs some better checking
+            # for 2D cases
+            if ((is_list_like(new) and
+                 np.any(mask[mask]) and
+                 getattr(new, 'ndim', 1) == 1)):
+
+                if not (mask.shape[-1] == len(new) or
+                        mask[mask].shape[-1] == len(new) or
+                        len(new) == 1):
+                    raise ValueError("cannot assign mismatch "
+                                     "length to masked array")
+
             np.putmask(new_values, mask, new)
 
         # maybe upcast me