Duplicate email remover for Sendy

import os

#1. Export all subscribers from the customer list and the muy molon list
#2. Run this script
#3. In Sendy, chose mass delete and upload the duplicates.csv file.

customer_list_to_keep_as_string = open('all-spanish-customers.csv', 'r').read()

list_to_filter = open('list-to-filter-all.csv', 'r')

duplicate_file = open('duplicates.csv', 'w')

line = list_to_filter.readline()
number_of_duplicates = 0
while line != "":
  email = line.split(",")[1].partition('\"')[-1].rpartition('\"')[0]
  if (customer_list_to_keep_as_string.find(email) != -1):
  	print("Duplicate: " + email)
  	number_of_duplicates = number_of_duplicates + 1
  	duplicate_file.write(email + "\n")
  line = list_to_filter.readline()

print ("Found " + str(number_of_duplicates) + " duplicates")

Python script to remove email in a csv. Using it for Prestsahop subscriver list to remove Sendy customers that has converted from only signups in the mailing list to real customers.