import pandas as pd
import numpy as np

visitor = [['Jack', 34, 'Australia', 'Sydney'] ,
             ['Riti', 30, 'India', 'Delhi' ] ,
             ['Aadi', 16, 'United States', 'New York'],
             ['Mary', 22, 'United States', 'New York'],
             ['Doug', 13, 'United States', 'Los Angeles'],
             ['Chad', 15, 'Australia', 'Sydney'],
             ['Alba', 32, 'United Kingdom', 'London']]

df = pd.DataFrame(visitor, columns=['Name','Age','Country', 'City'])

pd.pivot_table(df, index=['Country', 'City'], aggfunc='count')

Age    Name
Country           City
Australia         Sydney         2      2
India             Delhi          1      1
United Kingdom    London         1      1
United States     Los Angeles    1      1
                  New York       2      2

SELECT country, city, count(*) FROM visitor GROUP BY country, city

count
Country           City
Australia         Sydney         2
India             Delhi          1
United Kingdom    London         1
United States     Los Angeles    1
United States     New York       2