pandas 将两列与空值组合在一起

问题描述

我有一个包含两列的 df，我想合并两列而忽略 NaN 值.问题是有时两列都有 NaN 值，在这种情况下，我希望新列也有 NaN.示例如下:

I have a df with two columns and I want to combine both columns ignoring the NaN values. The catch is that sometimes both columns have NaN values in which case I want the new column to also have NaN. Here's the example:

df = pd.DataFrame({'foodstuff':['apple-martini', 'apple-pie', None, None, None], 'type':[None, None, 'strawberry-tart', 'dessert', None]})

df
Out[10]:
foodstuff   type
0   apple-martini   None
1   apple-pie   None
2   None    strawberry-tart
3   None    dessert
4   None    None

我尝试使用 fillna 并解决这个问题:

I tried to use fillna and solve this :

df['foodstuff'].fillna('') + df['type'].fillna('')

我得到:

0      apple-martini
1          apple-pie
2    strawberry-tart
3            dessert
4
dtype: object

第 4 行变成了空值.在这种情况下我想要的是 NaN 值，因为两个组合列都是 NaN.

The row 4 has become a blank value. What I wan't in this situation is a NaN value since both the combining columns are NaNs.

0      apple-martini
1          apple-pie
2    strawberry-tart
3            dessert
4            None
dtype: object

推荐答案

使用 fillna 在一列上，填充值为另一列:

Use fillna on one column with the fill values being the other column:

df['foodstuff'].fillna(df['type'])

结果输出:

0      apple-martini
1          apple-pie
2    strawberry-tart
3            dessert
4               None

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