masterlist = [row for row in c2]

list_ = [1, 2, 3, 4, 5] #or range(1, 6)
squares = [x*x for x in list_]
print squares
#[1, 4, 9, 16, 25]

masterlist = list(c2)

masterlist = [row[1] for row in c2]

import csv

with open('hosts.csv', 'rb') as hosts, open('masterlist.csv', 'rb') as master:
    with open('results.csv', 'wb') as results:
        reader = csv.reader(hosts)
        writer = csv.writer(results)

        master_indices = {r[1]: i for i, r in enumerate(csv.reader(master), 1)}

        for row in reader:
            index = master_indices.get(row[3])
            if index is not None:
                message = 'FOUND in master list (row {})'.format(index)
            else:
                message = 'NOT FOUND in master list'
            writer.writerow(row)