Is there a way to create a list of values out of existing column value in pandas?

Let’s say I have the following pandas dataframe:

I would like to create a new column with the value of ColB and -1 * ColB. The resulting dataframe should look like this:

How can I achieve this efficiently?

>Solution :

simple way:

df['ColC'] = df['ColB'].astype(str) + ", " + (df['ColB']*-1).astype(str)