d_csv2 = {}

with open('subscriber_info 02212018.csv', 'r') as f_csv2:
    csv_2 = csv.reader(f_csv2)
    for cols in csv_2:
        d_csv2[cols[1]] = cols[0], cols[2]


with open('subscribersWithMultipleDevices.csv', 'r') as f_csv1, open('output.csv', 'w', newline='') as f_output:
    csv_1 = csv.reader(f_csv1)
    csv_output = csv.writer(f_output)
    csv_output.writerow(['Customer', 'Email', 'First Name', 'Last Name', 'Serial Number', 'WAN MAC', 'IP ADD', 'Model',
                        'Last Contact', 'Circuit ID', 'n'])

    for cols in csv_1:
        try:
            if cols[6] in d_csv2:
                csv_output.writerow(cols + [d_csv2[cols[6]]])
        except KeyError:
            print('key error')