Pandas 数据框替换多列条件下的值

Question

I have a dataframe df_merchandise with two columns of interest, ProductType and ProductDescription. One of the values for ProductType is 'Accessory' which can have multiple different values for ProductDescription, such as 'Lamp', 'Mirror', etc. How would I do a conditional replacement like the following:

If (df_merchandise.ProductType == 'Accessory') and (df_merchandise.ProductDescription == 'Mirror'):
     replace 'Accessory' with 'Mirror'

The key here being that I only replace the value of ProductType for ProductDescription if the row value for PType is 'accessory' AND the row value for PDesc. is 'Mirror'.

Answer 1

If your original DF is

  ProductDescription ProductType
0                Art   Accessory
1             Mirror   Accessory
2        Western Art   Accessory
3             Tassel   Accessory
4           Hardware   Accessory
5             Mirror   Accessory

You can do the following:

mirror_filter = (df['ProductType'] == 'Accessory') & (df['ProductDescription'] == 'Mirror')
df.loc[mirror_filter, 'ProductType'] = df['ProductDescription']

And your resulting DF should be:

  ProductDescription ProductType
0                Art   Accessory
1             Mirror      Mirror
2        Western Art   Accessory
3             Tassel   Accessory
4           Hardware   Accessory
5             Mirror      Mirror