如何在空值上折叠 pandas 中的列？ [英] how to collapse columns in pandas on null values?

问题描述

假设我有以下数据框：

pd.DataFrame({'col1':    ["a", "a", np.nan, np.nan, np.nan],
            'override1': ["b", np.nan, "b", np.nan, np.nan],
            'override2': ["c", np.nan, np.nan, "c", np.nan]})


    col1    override1   override2
0     a        b          c
1     a       NaN        NaN
2     NaN      b         NaN
3     NaN     NaN         c
4     NaN     NaN         NaN

有没有一种方法可以将3列折叠为一列，其中 override2 会覆盖 override1 ，它会覆盖 col1 ，但是，如果存在NaN，则必须保留bofore的值？另外，我主要是在寻找一种无需增加额外专栏的方法。我真的在寻找内置的熊猫解决方案。

Is there a way to collapse the 3 columns into one column, where override2 overrides override1, which overrides col1, however, in case there is NaN, then the values bofore is to be kept? Also, I am mainly looking for a way where I would not have to make an additional column. I am really looking for a built-in pandas solution.

这是我正在寻找的输出：

This is the output I am looking for:

 collapsed
0  c
1  a
2  b
3  c
4  NaN

推荐答案

使用填充

df.ffill(1).iloc[:,-1]

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