fixed iloc bug

dios/indexer.py

@@ -61,14 +61,22 @@ class _Indexer:
                     dat_xloc = getattr(dat, xloc)
                     val = value[i] if iter else value
 
+                    # a hashable rowkey (.xloc[3, c] = value) :
+                    #   loc:  rowkey not present in self -> prevent that .loc create a new item
+                    #   loc:  rowkey present in self -> OK
+                    #   iloc: OK (cannot set a new item)
                     if _is_hashable(rowkey):
-                        # prevent setting a new value with .loc
-                        if rowkey not in dat:
+                        if xloc == 'loc' and rowkey not in dat:
                             raise KeyError(rowkey)
-                    else:
-                        # cannot set to empty series
-                        if len(dat_xloc[rowkey]) == 0:
-                            continue
+
+                    # not a hashable rowkey (.xloc[[3,4], c] = value),
+                    # so we can ask for a length, otherwise we might get a single value
+                    # returned, that has no length. But we need to do this check, because,
+                    # setting a value to an empty series, always fail.
+                    # Nevertheless, if any key doesn't exist, the correct KeyError is thrown here,
+                    # instead of later.
+                    elif len(dat_xloc[rowkey]) == 0:
+                        continue
 
                     dat_xloc[rowkey] = val