替换Python Datafram中的空白

Question

我知道有很多关于这个的帖子，我也读了很多，但我似乎什么都做不到

                            O         H         L         C   MLR_CQG
DateTime                                                             
2011-09-19 22:00:00   -0.3606   -0.3605   -0.3611   -0.3611 -0.361171
2011-09-19 23:00:00   -0.3611   -0.3611   -0.3614   -0.3614 -0.361202
2011-09-20 00:00:00   -0.3614   -0.3602   -0.3614   -0.3613 -0.361344
2011-09-20 01:00:00                                         -0.361571
2011-09-20 02:00:00   -0.3613   -0.3613   -0.3614   -0.3613 -0.361752
2011-09-20 03:00:00   -0.3613   -0.3601   -0.3613   -0.3607 -0.361806
2011-09-20 04:00:00   -0.3611   -0.3607   -0.3614   -0.3608 -0.361845
2011-09-20 05:00:00   -0.3607   -0.3596   -0.3614   -0.3596 -0.361806
2011-09-20 06:00:00   -0.3603   -0.3594   -0.3604   -0.3601 -0.361796
2011-09-20 07:00:00   -0.3601   -0.3595   -0.3601   -0.3597 -0.361725
2011-09-20 08:00:00   -0.3599   -0.3599   -0.3613   -0.3607 -0.361753
2011-09-20 09:00:00   -0.3609   -0.3603   -0.3641    -0.363 -0.362013
2011-09-20 10:00:00   -0.3631   -0.3617   -0.3636   -0.3634 -0.362320
2011-09-20 11:00:00   -0.3635    -0.363   -0.3647   -0.3643 -0.362667
2011-09-20 12:00:00   -0.3642   -0.3639   -0.3651   -0.3647 -0.362993
2011-09-20 13:00:00   -0.3644   -0.3644   -0.3654    -0.365 -0.363288
2011-09-20 14:00:00   -0.3651   -0.3636   -0.3652   -0.3645 -0.363558
2011-09-20 14:30:00   -0.3646   -0.3636   -0.3649   -0.3641 -0.363725
2011-09-20 15:30:00   -0.3637   -0.3627   -0.3644   -0.3643 -0.363879
2011-09-20 16:30:00   -0.3637   -0.3629   -0.3638   -0.3629 -0.363929
2011-09-20 18:00:00                                         -0.363892
2011-09-20 19:00:00   -0.3636   -0.3627   -0.3637   -0.3627 -0.363812

我基本上只想用上面一行的数据替换空单元格。我试过这行代码，但它似乎不能替换空单元格。这也是一个将运行数千次的进程的一部分——如果可能的话，我不希望执行任务，除非有空行。你知道吗

rbs_test.replace(r'^\s*$', np.nan, regex=True).fillna(method='ffill')