根据不同列的值，从pandas列表列获取列表元素

Question

我有一个Pandas DataFrame，其中包含一个列表列，如下所示。

    selection  weeks
0   2            [43, 44, 45, 46, 47, 48, 49, 50, 51, 52]
1   3            [43, 44, 45, 46, 47, 48, 49, 50, 51, 52]
2   1            [43, 44, 45, 46, 47, 48, 49, 50, 51, 52]

我该如何根据选择值获取前N个元素以获得以下结果？

    selection  weeks                                     select_week 
0   2          [43, 44, 45, 46, 47, 48, 49, 50, 51, 52]  [43, 44]
1   3          [43, 44, 45, 46, 47, 48, 49, 50, 51, 52]  [43, 44, 45]
2   1          [43, 44, 45, 46, 47, 48, 49, 50, 51, 52]  [43]

- d.r.

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列表的长度在整个“weeks”列中是否保持一致？ - Ch3steR

@Ch3steR - 是的。 - d.r.

Answer 1

使用索引选择列表推导式：

df['select_week'] = [x[:y] for x, y in df[['weeks','selection']].to_numpy()]

或者DataFrame.apply：

df['select_week'] = df.apply(lambda x: x['weeks'][:x['selection']], axis=1)

- jezrael

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嗨。我有一个愚蠢的疑问。为什么这个不起作用？df.weeks.str[0: df.selection]？ - Mayank Porwal

@MayankPorwal - 因为.str[:N]仅适用于标量，所以无法传递另一列。 - jezrael