ean13码的生成，python读取csv中数据并处理返回并写入到另一个csv文件中

# -*- coding: utf-8 -*-
import math
import re
import csv
import repr
def ean_checksum(eancode):
"""returns the checksum of an ean string of length 13, returns -1 if the string has the wrong length"""
if len(eancode) != 13:
return -1
oddsum=0
evensum=0
total=0
eanvalue=eancode
reversevalue = eanvalue[::-1]
finalean=reversevalue[1:]

for i in range(len(finalean)):
if i % 2 == 0:
oddsum += int(finalean[i])
else:
evensum += int(finalean[i])
total=(oddsum * 3) + evensum

check = int(10 - math.ceil(total % 10.0)) %10
return check

def sanitize_ean13(csvfile):
reader = csv.reader(file(csvfile,'rb'))
writer = csv.writer(file('C:/Users/Administrator/Desktop/1.csv','wb'))
for id,ean13 in reader:
if not ean13:
return "0000000000000"
ean13 = str(ean13)
ean13 = '0' * (9-len(ean13)) + ean13
ean13 = '042' + ean13
ean13 = re.sub("[A-Za-z]","0",ean13);
ean13 = re.sub("[^0-9]","",ean13);
ean13 = ean13[:13]
if len(ean13) < 13:
ean13 = ean13 + '0' * (13-len(ean13))
s=ean13[:-1] + str(ean_checksum(ean13))
writer.writerow([id,s])
sanitize_ean13('C:/Users/Administrator/Desktop/res.partner.csv')