Fillna on片，在其他数据帧中

Question

我想要更改一个函数，该函数将指示器列中的单个值填充为填充Nan (0)--堆叠数据格式的值列，以处理指示符的列表，其中的Nan值应设置为零。

import pandas as pd
import numpy as np

df = pd.DataFrame({'ISO3': ['Australia', 'Austria', 'Belgium', 'Canada', 'Australia', 'Austria', 'Belgium', 'Canada'], 
                   'Year': [1991, 1991, 1991, 1991, 1991, 1991, 1991, 1991],
                   'Indicator' : ['Disaster Fatalities', 'Disaster Fatalities', 'Disaster Fatalities', 'Disaster Fatalities', 'Oil Reserves', 'Oil Reserves', 'Oil Reserves', 'Oil Reserves' ],
                   'Value' : [np.nan, 5, np.nan, 18, np.nan, np.nan, np.nan, np.nan]
                  })
df.head(8)

给予：

ISO3    Year    Indicator   Value
0   Australia   1991    Disaster Fatalities NaN
1   Austria 1991    Disaster Fatalities 5.0
2   Belgium 1991    Disaster Fatalities NaN
3   Canada  1991    Disaster Fatalities 18.0
4   Australia   1991    Oil Reserves    NaN
5   Austria 1991    Oil Reserves    NaN
6   Belgium 1991    Oil Reserves    NaN
7   Canada  1991    Oil Reserves    NaN

函数，将单个指示符的Nan值设置为零：

def zerofillnaindicator (df, Indicators):
    mask = (df['Indicator'] == Indicators)
    df.loc[mask, 'Value'] = df.loc[mask, 'Value'].fillna(0)
    return df

用

df2 = zerofillnaindicator (df = df, Indicators = 'Disaster Fatalities')
df2.head(8)

按需要给予：

ISO3    Year    Indicator   Value
0   Australia   1991    Disaster Fatalities 0.0
1   Austria 1991    Disaster Fatalities 5.0
2   Belgium 1991    Disaster Fatalities 0.0
3   Canada  1991    Disaster Fatalities 18.0
4   Australia   1991    Oil Reserves    NaN
5   Austria 1991    Oil Reserves    NaN
6   Belgium 1991    Oil Reserves    NaN
7   Canada  1991    Oil Reserves    NaN

但是，我如何改变这一点，以获得这样的指标清单：

df2 = zerofillnaindicator (df = df, Indicators = ['Disaster Fatalities', 'Oil Reserves'])
df2.head(8)

我尝试用df.isin(Indicators)替换掩码的条件，但这导致了.isin函数上的“不能用多维键进行索引”错误。

def zerofillnaindicator (df, Indicators):
    mask = df.isin(Indicators)
    df.loc[mask, 'Value'] = df.loc[mask, 'Value'].fillna(0)
    return df

Answer 1

如果需要在同一个函数中处理标量或列表，请使用isinstance将标量转换为一个元素列表：

def zerofillnaindicator (df, Indicators):
    vals = [Indicators] if isinstance(Indicators, str) else Indicators

    mask = df['Indicator'].isin(vals)
    df.loc[mask, 'Value'] = df.loc[mask, 'Value'].fillna(0)
    return df

df2 = zerofillnaindicator (df = df, Indicators = 'Disaster Fatalities')
print (df2)
        ISO3  Year            Indicator  Value
0  Australia  1991  Disaster Fatalities    0.0
1    Austria  1991  Disaster Fatalities    5.0
2    Belgium  1991  Disaster Fatalities    0.0
3     Canada  1991  Disaster Fatalities   18.0
4  Australia  1991         Oil Reserves    NaN
5    Austria  1991         Oil Reserves    NaN
6    Belgium  1991         Oil Reserves    NaN
7     Canada  1991         Oil Reserves    NaN

df3 = zerofillnaindicator (df = df, Indicators = ['Disaster Fatalities', 'Oil Reserves'])
print (df3)
        ISO3  Year            Indicator  Value
0  Australia  1991  Disaster Fatalities    0.0
1    Austria  1991  Disaster Fatalities    5.0
2    Belgium  1991  Disaster Fatalities    0.0
3     Canada  1991  Disaster Fatalities   18.0
4  Australia  1991         Oil Reserves    0.0
5    Austria  1991         Oil Reserves    0.0
6    Belgium  1991         Oil Reserves    0.0
7     Canada  1991         Oil Reserves    0.0