invert.py

import csv

def invert(filename):
    with open(filename + ".csv", "rb") as csvfile:
        reader = csv.reader(csvfile, delimiter=",", quotechar='"')
        with open(filename + "_inverted.csv", "wb") as csvfilew:
            writer = csv.writer(csvfilew, delimiter=",", quotechar='"', quoting=csv.QUOTE_ALL)
            first_done = False
            for row in reader:
                if first_done:
                    row[1] = float(row[1]) * -1
                first_done = True
                writer.writerow(row)
            
invert("20140305-20150511-for-xero-import-new-cols")
invert("20150406-20150304-from-pdf-statements-rewritten")