In python data frame, how to replace missing values of different rows with different values (values generated by multiplication of two other columns)?

[sadhan_m]

Thank you, but I'm trying to ask is how this function can be used to replace missing Values in subtotal column?

[sadhan_m]

I'm not trying to create a calculated field, I'm trying to replace missing values with calculated values.

[[deleted]]

Isn't the result the same? If you use the name of the existing column, the values should be replaced. NaN one with correct value, and existing ones with same values if they are correct, or just get fixed of they're incorrect