我已经阅读了一个csv文件并将其转为以下结构:pivoted=df.pivot('user_id','group','value')lookup=df.drop_duplicates('user_id')[['user_id','group']]lookup.set_index(['user_id'],inplace=True)result=pivoted.join(lookup)result=result.fillna(0)部分结果:012345678910111213groupuser_id23365323259167208671873106342569215l-141889541