Subsetting data using a boolean column with Pandas

I would like to create a new column (D) that contains only the data from column (B) that satisfy the boolean condition from column (C), with "NA" for the false condition.

For example, here is my original table.

I’d like to use the boolean column (C) to subset column (B) into a new column (D) like so..

>Solution :

Use df['C'] as a condition in np.where:

df['D'] = np.where(df['C'], df['B'], np.nan)

Output:

   A      B      C    D
0  1    car   True  car
1  2    car   True  car
2  3   bike  False  NaN
3  4  house  False  NaN