For columns with numeric data you should use GetItemNumber() or GetItemDecimal().
If your target column in dw_1 is of type string, you have to "cast" the value,
because dw.SetItem () expects the columns datatype.
So if the column's datatype in dw_1 and dw_2 do not match, use something like this.
dw_1.setitem(row, column_name, String (dw_2.GetItemNumber(ll_newrow, column_name)))
hth
Arnd