df2.<TAB>  # df2 后按TAB键，可显示如下
df2.A            df2.abs        df2.add        df2.add_prefix
df2.add_suffix   df2.align      df2.all        df2.any
df2.append       df2.apply      df2.applymap   df2.as_blocks
df2.asfreq       df2.as_matrix  df2.astype     df2.at
df2.at_time      df2.boxplot    df2.C          df2.clip
df2.clip_lower   df2.clip_upper df2.columns    df2.combine
df2.combineAdd   df2.combine_first             df2.combineMult
df2.compound     df2.consolidate.              df2.convert_objects
df2.copy         df2.corr       df2.corrwith   df2.count
df2.axes.        df2.B          df2.bfill.     df2.between_time
df2.blocks       df2.bool       df2.cov        df2.cummax
df2.cummin.      df2.cumprod    df2.cumsum.    df2.D