np.where
https://blog.csdn.net/erinapple/article/details/80838359
tmp = data.assign(**{'ws^2': data.apply(lambda row: sum(row['ws'] * np.where(
row['factor'] == data['factor'], data['ws'], 0.0)), axis=1)})
https://blog.csdn.net/erinapple/article/details/80838359
tmp = data.assign(**{'ws^2': data.apply(lambda row: sum(row['ws'] * np.where(
row['factor'] == data['factor'], data['ws'], 0.0)), axis=1)})