Python:从现有列创建新列 [英] Python: create a new column from existing columns

问题描述

我正在尝试根据两个列创建一个新列.假设我要创建一个新列z，并且当它不丢失时应为y的值，而当y确实不存在时应为x的值.因此，在这种情况下，我希望z为 [1、8、10、8] .

I am trying to create a new column based on both columns. Say I want to create a new column z, and it should be the value of y when it is not missing and be the value of x when y is indeed missing. So in this case, I expect z to be [1, 8, 10, 8].

   x   y
0  1 NaN
1  2   8
2  4  10
3  8 NaN

推荐答案

新列'z'使用 df从列'y'中获取其值['z'] = df ['y'] .这会遗漏缺少的值，因此请使用 fillna 并使用列'x'填充它们.链接这两个动作:

The new column 'z' get its values from column 'y' using df['z'] = df['y']. This brings over the missing values so fill them in using fillna using column 'x'. Chain these two actions:

>>> df['z'] = df['y'].fillna(df['x'])
>>> df
   x   y   z
0  1 NaN   1
1  2   8   8
2  4  10  10
3  8 NaN   8

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