pandas total number of employees missing value complement

Since the securities report showing the total number of employees is published only once a year, there is a missing value in the total number of employees. Therefore, I will try to make up for the gap between them! This time, we supplemented to refer to the number of employees in the previous term.

Current status

Target

python

df['Total number of employees'] = df.groupby(['Ticker'])['Total number of employees'].apply(lambda d: d.fillna(d.interpolate(method='pad', limit=3)))