熊猫在不同索引上的前向和后向填充

Question

我具有以下数据框df：

             length       timestamp       width
name                                          
testschip-1     NaN 2019-08-01 00:00:00    NaN
testschip-1     NaN 2019-08-01 00:00:09    NaN
testschip-1     2   2019-08-01 00:00:20    NaN
testschip-1     2   2019-08-01 00:00:27    NaN
testschip-1     NaN 2019-08-01 00:00:38    1
testschip-2     4   2019-08-01 00:00:39    2
testschip-2     4   2019-08-01 00:00:57    NaN
testschip-2     4   2019-08-01 00:00:58    NaN
testschip-2     NaN 2019-08-01 00:01:17    NaN
testschip-3     NaN 2019-08-01 00:02:27    NaN
testschip-3     NaN 2019-08-01 00:03:47    NaN

首先，我想从索引“名称”中删除字符串“ testschip-”，因此我只能在索引上获得整数。其次，对于每个唯一索引，我都希望在“长度”和“宽度”两列上应用前向填充或后向填充（无论是否需要获得NaN）。每个唯一索引都具有相同的“长度”和“宽度”。在“ testschip-3”上，我不想应用向后或向前填充。如果我向后填充“ testschip-1”（需要将前两个索引设置为2'2'，那么对于索引“ testschip-1”的最后一行，我会得到一个不必要的“ 4”）。我无法事先判断是否必须事先应用向后填充或向前填充，因为我要开始处理400万行数据。

Answer 1

用途：

df.index = df.index.str.lstrip('testschip-').astype(int)
df.groupby(level = 0).apply(lambda x: x.bfill().ffill())

输出

      length           timestamp  width
name                                   
1        2.0 2019-08-01 00:00:00    1.0
1        2.0 2019-08-01 00:00:09    1.0
1        2.0 2019-08-01 00:00:20    1.0
1        2.0 2019-08-01 00:00:27    1.0
1        2.0 2019-08-01 00:00:38    1.0
2        4.0 2019-08-01 00:00:39    2.0
2        4.0 2019-08-01 00:00:57    2.0
2        4.0 2019-08-01 00:00:58    2.0
2        4.0 2019-08-01 00:01:17    2.0
3        NaN 2019-08-01 00:02:27    NaN
3        NaN 2019-08-01 00:03:47    NaN