Got the answer from Stack overflow as:
pd.merge(df_original,
df.groupby('website')['amount_views'].mean().to_frame('average_views'),
left_on='website',right_index=True,how='left')
Got the answer from Stack overflow as:
pd.merge(df_original,
df.groupby('website')['amount_views'].mean().to_frame('average_views'),
left_on='website',right_index=True,how='left')