With in a loop I have few dataframes created. I can union them with out an issue if they have same schema using (df_unioned = reduce(DataFrame.unionAll, df_list). Now my problem is how to union them if one of the dataframe in df_list has different number of columns? I thought, reduce(df_unioned=DataFrame.unionByName, df_list, allowMissingColumns=True) would solve the issue but it is giving me error: reduce() takes no keyword arguments. Thanks in advance. Let me know if you need any details in the question.