Transform a Blinksale XML document into list of invoices in CSV format

blinksale.py

#!/usr/bin/env python

'''Transform a Blinksale XML document into list of invoices in CSV format'''

__author__ = 'Ryan Blunden'
__copyright__ = 'Copyright 2012, Ryan Blunden'
__license__ = 'GPL'

import sys
import csv
from lxml import etree

def blinksale(input_file, output_file):
    root = etree.XML(open(input_file, 'r').read())
    output = csv.writer(open(output_file, 'w'), dialect='excel')
    output.writerow(['Client Name', 'Invoice Date', 'Invoice ID', 'Subtotal', 'Tax', 'Total'])
    clients = []
    for child in root.iterchildren():
        if child.tag == 'clients':
            clients = child
            break

    for client in clients.iterchildren():
        client_name = client[0].text
        for invoice in client[-2].iterchildren():
            invoice_number = invoice[1].text
            invoice_date = invoice[4].text
            invoice_tax = invoice[7].items()[0][1]
            invoice_total = invoice[-2].items()[0][1]
            output.writerow([client_name, invoice_date, invoice_number, invoice_total, invoice_tax, invoice_total])

if __name__ == '__main__':
    if len(sys.argv) < 3:
        print 'Usage: %s blinksale.xml invoices.csv' % sys.argv[0]
        sys.exit(1)

    blinksale(sys.argv[1], sys.argv[2])