Update column of a dataframe when key matches from another dataframe in pandas

Question

I have two dataframes.

For all rows in df1, find the corresponding row in df2 (through matching key) and update the final column in df2 to 1. How shall I proceed in pandas?

Answer 1

Remove column final, use left join with indicator parameter, so is possible create 1,0 column by mapping True, False by compare both:

df = df2.drop('final', axis=1).merge(df1, how='left', indicator='final')
df['final'] = df['final'].eq('both').astype(int)