熊猫 - get_dummies 乘以数量

Question

I have a pandas.DataFrame with Stockcode and quantity:

>>>df
    StockCode   Quantity
0   85123A      6
1   71053       6
2   84406B      8
3   84029G      6
4   84029E      6

I'm looking for a solution to get the pandas.get_dummies() multiplied by the quantity.

The output I'm expecting should look like that:

>>>pd.get_dummies(df['StockCode']) ... --> * df['Quantity']
    71053   84029E  84029G  84406B  85123A
0   0       0       0       0       6
1   6       0       0       0       0
2   0       0       0       8       0
3   0       0       6       0       0
4   0       6       0       0       0

I can do a for loop to multiply all the dummies by the quantity, but I'm hoping a more "pythonic" solution.

Does anyone know if there is better way to get those corrected dummies ?

Thanks

Larry

Answer 1

df.reset_index().pivot('index','StockCode','Quantity').fillna(0)
Out[93]: 
StockCode  71053  84029E  84029G  84406B  85123A
index                                           
0            0.0     0.0     0.0     0.0     6.0
1            6.0     0.0     0.0     0.0     0.0
2            0.0     0.0     0.0     8.0     0.0
3            0.0     0.0     6.0     0.0     0.0
4            0.0     6.0     0.0     0.0     0.0

To fix your code

pd.get_dummies(df['StockCode']).mul(df.Quantity,0)
Out[97]: 
   71053  84029E  84029G  84406B  85123A
0      0       0       0       0       6
1      6       0       0       0       0
2      0       0       0       8       0
3      0       0       6       0       0
4      0       6       0       0       0

Or pd.get_dummies(df['StockCode']).values*df.Quantity.values[:,None]

Answer 2

This also works

df.StockCode.str.get_dummies().mul(df.Quantity, axis=0)

Reference

How to multiply each row in pandas dataframe by a different value

https://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.str.get_dummies.html