My current data is organised into two data frames of the same shape. Id then like to sum all columns into a single column after calculation.

I am doing this using:

```
    df = df1_kwh.multiply(df2np).sum(axis=1)

```

However when I use df.shape i get a shape of "(347,)" meaning no columns and I am then unable to add additional columns to the "sum" value column using df.insert.

What can I do to make the output of df.sum able to be manipulated by other functions?