Pandas条件创建seriesdataframe列

Pandas条件创建series/dataframe列

如果你只有两种选择：

df['color'] = np.where(df['Set']=='Z', 'green', 'red')

例如，

import pandas as pdimport numpy as npdf = pd.Dataframe({'Type':list('ABBC'), 'Set':list('ZZXY')})df['color'] = np.where(df['Set']=='Z', 'green', 'red')print(df)

输出

  Set Type  color0   Z    A  green1   Z    B  green2   X    B    red3   Y    C    red

如果你有两个以上的条件，请使用

np.select

。例如，如果你想

color

成为

• yellow

  when

  (df['Set'] == 'Z') & (df['Type'] == 'A')

• otherwise

  blue

  when

  (df['Set'] == 'Z') & (df['Type'] == 'B')

• otherwise

  purple

  when

  (df['Type'] == 'B')

• otherwise

  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)

输出：

  Set Type   color0   Z    A  yellow1   Z    B    blue2   X    B  purple3   Y    C   black