COLUMN 0
some@email.com
some@email.com
another@address.com
example@email.com

COLUMN 0                 COLUMN 1
some@email.com           2
another@address.com      1
example@email.com        1

import csv

f = csv.reader(open('infile.csv','rb'))
writer = csv.writer(open('outfile.csv','wb'))
emails = set()


for row in f:
    if row[0] not in emails:
        writer.writerow(row)
        emails.add( row[0] )

from collections import defaultdict

# count all the emails before we write anything out
emails = defaultdict(int)
for row in f:
    emails[row[0]] += 1

# now write the file
for row in email.items():
    writer.writerow(row)

from collections import Counter

emails=Counter()
for row in f:
    emails+=Counter([row[0]])

Counter({'some@email.com': 2, 'another@address.com': 1, 'example@email.com': 1, 'COLUMN 0': 1})

print set(emails.elements())
# set(['another@address.com', 'COLUMN 0', 'example@email.com', 'some@email.com'])