The groupby, if done using itertools, will cut some code. from itertools import groupby customer_data = (line.strip().split(',') for line in file('cus

The groupby, if done using itertools, will cut some code. from itertools import groupby customer_data = (line.strip().split(',') for line in file('customer.txt')) grouped_ages = groupby(customer_data, key=itemgetter(1)) print sorted((len(list(g)), k) for k, g in grouped_ages)[-3:]