如何将 color
列添加到以下数据帧,以便 color='green'
如果 set == 'z'
,否则 color='red'
?
Type Set
1 A Z
2 B Z
3 B X
4 C Y
正确答案
如果您只有两个选择,请使用 np.where
:
df['color'] = np.where(df['set']=='z', 'green', 'red')
例如,
import pandas as pd
import numpy as np
df = pd.dataframe({'type':list('abbc'), 'set':list('zzxy')})
df['color'] = np.where(df['set']=='z', 'green', 'red')
print(df)
产量
set type color
0 z a green
1 z b green
2 x b red
3 y c red
如果您有两个以上的条件,请使用 np.select
。例如,如果您希望 color
为
yellow
当(df['set'] == 'z') & (df['type'] == 'a')
- 否则
blue
当(df['set'] == 'z') & (df['type'] == 'b')
- 否则
purple
当(df['type'] == 'b')
- 否则
black
,
然后使用
df = pd.dataframe({'type':list('abbc'), 'set':list('zzxy')})
conditions = [
(df['set'] == 'z') & (df['type'] == 'a'),
(df['set'] == 'z') & (df['type'] == 'b'),
(df['type'] == 'b')]
choices = ['yellow', 'blue', 'purple']
df['color'] = np.select(conditions, choices, default='black')
print(df)
产生
Set Type color
0 Z A yellow
1 Z B blue
2 X B purple
3 Y C black