Update specific column values based upon group by from different column in Pandas

Question

I have below pandas data frame in python.

Looking for below output:

Based upon group of last column I need to pick and repeat first value from and in middle column.

Answer 1

Try:

df['col1'] = df['col1'].mask(df['col2'].duplicated()).ffill()

Or:

df['col1'] = df.groupby('col2')['col1'].transform('first')