Python Pandas 计算两列的 value_counts 并使用 groupby

Question

我有一个数据框：

data = {'label': ['cat','dog','dog','cat','cat'],
      'breeds': [ 'bengal','shar pei','pug','maine coon','maine coon'],
      'nicknames':[['Loki','Loki' ],['Max'],['Toby','Zeus ','Toby'],['Marty'],['Erin ','Erin']],
       'eye color':[['blue','green'],['green'],['brown','brown','brown'],['blue'],['green','brown']]
                   

输出：

label    breeds    nicknames            eye color
0   cat  bengal     [Loki,Loki]      [blue, green]
1   dog  shar pei   [Max]            [green]
2   dog  pug        [Toby,Zeus,Toby] [brown, brown, brown]
3   cat  maine coon [Marty]          [blue]
4   cat  maine coon [Erin,Erin]      [green, brown]

我想应用groupby :frame['label', 'breeds']，计算昵称和眼睛颜色的value_counts（唯一值），输出到不同的列: 'nickname_count','eye_count' 这段代码只输出一列，如何分别输出？

 frame2=frame.groupby(['label','breeds'])['nicknames','eye color'].apply(lambda x: x.astype('str').value_counts().to_dict())

Answer 1

首先，我们在列表中使用groupby 和sum，因为sum 将列表连接在一起：

>>> df_grouped = df.groupby(['label', 'breeds']).agg({'nicknames': sum, 'eye color': sum}).reset_index()
>>> df_grouped
    label   breeds      nicknames               eye color
0   cat     bengal      [Loki, Loki]            [blue, green]
1   cat     maine coon  [Marty, Erin , Erin]    [blue, green, brown]
2   dog     pug         [Toby, Zeus , Toby]     [brown, brown, brown]
3   dog     shar pei    [Max]                   [green]

然后，我们可以通过将列表转换为集合来计算列表中唯一值的数量，使用len 并将输出保存在两个新列中以获得预期结果：

>>> df_grouped['nickname_count'] = df_grouped['nicknames'].apply(lambda x: list(set(x))).str.len()
>>> df_grouped['eye_count'] = df_grouped['eye color'].apply(lambda x: list(set(x))).str.len()
>>> df_grouped
    label   breeds      nicknames               eye color               nickname_count  eye_count
0   cat     bengal      [Loki, Loki]            [blue, green]           1               2
1   cat     maine coon  [Marty, Erin , Erin]    [blue, green, brown]    3               3
2   dog     pug         [Toby, Zeus , Toby]     [brown, brown, brown]   2               1
3   dog     shar pei    [Max]                   [green]                 1               1