pandas groupby to calculate percentage of groupby columns
You can do -
df = df.groupby(['location']).agg({'new_deaths': sum, 'population': max})
df['rate_death'] = df['new_deaths'] / df['population'] * 100
Result
new_deaths population rate_death
location
Afghanistan 15 38928341 0.000039
Albania 1 2877800 0.000035