python - 如何根据条件更改python数据框中的值(即列表)？

Question

我有一个包含歌曲信息的数据帧'songDataFrame'。共有三列:“艺术家”、“标题”、“流派”。前两个是字符串，'genres' 包含流派列表。它看起来像这样:

id  artist             title         genres
1   'Sarah Bareilles'  'Opening Up'  ['acoustic','pop', 'piano']
2   'Post Malone'      'Stay'        ['Hip-Hop', 'rap', 'trap']
3   'Dean Lewis'       'Waves'       ['alternative', 'guitar', 'indie']
4   'Billie Eilish'    'Watch'       ['indie', 'indie pop', 'pop']
5   'Passenger'        'Let Her Go'  ['metal', 'screamo', 'gore']

艺术家“Passenger”的流派是错误的。我想将现有列表更改为 ['indie rock', 'folk rock']。

如果它不是一个列表，但我用一个字符串替换，我就会这样做:

mask = songDataFrame.artist =='Passenger'
songDataFrame.loc[mask, 'genres'] = 'indie folk'

这样就可以正常工作了。当我用['独立摇滚'，'民间摇滚']代替'独立民谣'时，

mask = songDataFrame.artist =='Passenger'
songDataFrame.loc[mask, 'genres'] = ['indie folk','folk rock']

我收到此错误:

ValueError: Must have equal len keys and value when setting with an iterable

有办法解决吗？

Answer 1

使用两行并使用loc分配一个字符串，将所有列值设置为字符串，然后将它们返回到列表:

import ast
songDataFrame.loc[songDataFrame['artist']=='Passenger','genres']="['indie folk','folk rock']"
songDataFrame['genres']=songDataFrame['genres'].astype(str).apply(ast.literal_eval)

现在:

print(songDataFrame)

是:

   id           artist       title                        genres
0   1  Sarah Bareilles  Opening Up        [acoustic, pop, piano]
1   2      Post Malone        Stay          [Hip-Hop, rap, trap]
2   3       Dean Lewis       Waves  [alternative, guitar, indie]
3   4    Billie Eilish       Watch       [indie, indie pop, pop]
4   5        Passenger  Let Her Go       [indie folk, folk rock]