替换 pandas 中的列值的最佳方法？

Question

What is the best way to such an operation:

data[col] = data[col].fillna(0)

I just want to replace the values of a column without raising the warning:

SettingWithCopyWarning: 
A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead

Answer 1

The suggestion works:

d = {'date': ['2020-01','2020-01','2020-02','2020-02','2020-03','2020-03','2020-04','2020-04',], 'A': [1,2,np.nan,4,5,6,7,8]}
df = pd.DataFrame(data=d)
print(df)
          date    A
0  2020-01  1.0
1  2020-01  2.0
2  2020-02  NaN
3  2020-02  4.0
4  2020-03  5.0
5  2020-03  6.0
6  2020-04  7.0
7  2020-04  8.0


df.loc[df['A'].isna(),'A']=0

print(df)

      date    A
0  2020-01  1.0
1  2020-01  2.0
2  2020-02  0.0
3  2020-02  4.0
4  2020-03  5.0
5  2020-03  6.0
6  2020-04  7.0
7  2020-04  8.0