I want to multiply two columns in a pandas DataFrame and add the result into a new column

Question

I\'m trying to multiply two existing columns in a pandas Dataframe (orders_df) - Prices (stock close price) and Amount (stock quantities) and add the calculation to a new co

Answer 1

For me, this is the clearest and most intuitive:

values = []
for action in ['Sell','Buy']:
    amounts = orders_df['Amounts'][orders_df['Action'==action]].values
    if action == 'Sell':
        prices = orders_df['Prices'][orders_df['Action'==action]].values
    else:
        prices = -1*orders_df['Prices'][orders_df['Action'==action]].values
    values += list(amounts*prices)  
orders_df['Values'] = values

The .values method returns a numpy array allowing you to easily multiply element-wise and then you can cumulatively generate a list by 'adding' to it.