python - 通过排除 Pandas 中另一列中的特定值来填充一列

Question

对于数据框 df ，我正在尝试填充列 b按值(value)2017-01-01如果列 a 中的值要么是空 NaNs或Others :

df = pd.DataFrame({'a':['Coffee','Muffin','Donut','Others',pd.np.nan, pd.np.nan]})
        a
0  Coffee
1  Muffin
2   Donut
3  Others
4     NaN
5     NaN

预期结果是这样的:

        a           b
0  Coffee  2017-01-01
1  Muffin  2017-01-01
2   Donut  2017-01-01
3  Others         NaN
4     NaN         NaN
5     NaN         NaN

我尝试过的方法并没有排除 NaNs :

df.loc[~df['a'].isin(['nan', 'Others']), 'b'] = '2017-01-01'

        a           b
0  Coffee  2017-01-01
1  Muffin  2017-01-01
2   Donut  2017-01-01
3  Others         NaN
4     NaN  2017-01-01
5     NaN  2017-01-01

谢谢!

Answer 1

使用np.nan代替nan:

df.loc[~df['a'].isin([np.nan, 'Others']), 'b'] = '2017-01-01'

或者在比较之前用其他替换缺失值:

df.loc[~df['a'].fillna('Others').eq('Others'), 'b'] = '2017-01-01'
print (df)
        a           b
0  Coffee  2017-01-01
1  Muffin  2017-01-01
2   Donut  2017-01-01
3  Others         NaN
4     NaN         NaN
5     NaN         NaN