python-3.x - 如果不是 NaN，Pandas 从列中获取值

Question

给定以下数据框:

import pandas as pd
import numpy as np
df = pd.DataFrame({'A':['One','Two',np.nan],
                   'B':[np.nan,np.nan,'Three'],
                   })
df

    A       B
0   One     NaN
1   Two     NaN
2   NaN     Three

我想创建一个列('C')，如果它不是这样的 NaN，则采用 'A' 或 'B' 的值:

    A       B        C
0   One     NaN      One
1   Two     NaN      Two
2   NaN     Three    Three

提前致谢!

Answer 1

您可以使用 combine_first :

df['C'] = df.A.combine_first(df.B)
print df                   
     A      B      C
0  One    NaN    One
1  Two    NaN    Two
2  NaN  Three  Three

或fillna :

df['C']= df.A.fillna(df.B)
print df                   
     A      B      C
0  One    NaN    One
1  Two    NaN    Two
2  NaN  Three  Three

或np.where如果两个条件都为假，则增加值(value)，例如1:

df['C'] = np.where(df.A.notnull(), df.A,np.where(df.B.notnull(), df.B, 1))
print df                   
     A      B      C
0  One    NaN    One
1  Two    NaN    Two
2  NaN  Three  Three