通过 Dataframe Pandas 中的索引从列数组中获取元素答案

【问题标题】：Get elements from column array by index in Dataframe Pandas通过 Dataframe Pandas 中的索引从列数组中获取元素
【发布时间】：2022-06-27 21:32:42
【问题描述】：

我有一个数据框：

import pandas as pd
data = {'id':[1,2,3],
            'tokens': [[ 'in', 'the' , 'morning',
                             'cat', 'run', 'today', 'very', 'quick'],['dog', 'eat', 'meat', 'chicken', 'from', 'bowl'],
                            ['mouse', 'hides', 'from', 'a', 'cat']]}
        
df = pd.DataFrame(data)

我还有一个索引列表。

lst_index = [[3, 4, 5], [0, 1, 2], [2, 3, 4]]

我想创建一个包含tokens 列数组中的元素的列。此外，这些元素由来自lst_index 的索引获取。所以它会是：

    id             tokens                                          new
0   1   [in, the, morning, cat, run, today, very, quick]    [cat, run, today]
1   2   [dog, eat, meat, chicken, from, bowl]               [dog, eat, meat]
2   3   [mouse, hides, from, a, cat]                        [from, a, cat]

【问题讨论】：

标签： python pandas dataframe

【解决方案1】：

使用简单的列表推导：

lst_index = [[3, 4, 5], [0, 1, 2], [2, 3, 4]]

df['new'] = [[l[i] for i in idx] for idx,l in zip(lst_index, df['tokens'])]

输出：

   id                                            tokens                new
0   1  [in, the, morning, cat, run, today, very, quick]  [cat, run, today]
1   2             [dog, eat, meat, chicken, from, bowl]   [dog, eat, meat]
2   3                      [mouse, hides, from, a, cat]     [from, a, cat]

【讨论】：

【解决方案2】：

你可以同时遍历字典和列表，获取new列：

data = {'id':[1,2,3],
            'tokens': [[ 'in', 'the' , 'morning',
                             'cat', 'run', 'today', 'very', 'quick'],['dog', 'eat', 'meat', 'chicken', 'from', 'bowl'],
                            ['mouse', 'hides', 'from', 'a', 'cat']]}
lst_index = [[3, 4, 5], [0, 1, 2], [2, 3, 4]]
l = []

for i in range(len(data["tokens"])):
    l.append([])
    for j in range(len(lst_index[i])):
        l[i].append(data["tokens"][i][lst_index[i][j]])

data["new"] = l
print(data)

输出：

{'id': [1, 2, 3], 'tokens': [['in', 'the', 'morning', 'cat', 'run', 'today', 'very', 'quick'], ['dog', 'eat', 'meat', 'chicken', 'from', 'bowl'], ['mouse', 'hides', 'from', 'a', 'cat']], 'new': [['cat', 'run', 'today'], ['dog', 'eat', 'meat'], ['from', 'a', 'cat']]}

【讨论】：