def save_pseudonyms():
    fn = os.path.abspath("pseudonyms.csv")
    print("Saving %d unique NHS Number pseudonyms to %s" % (len(LOOKUP), fn))

    f = open(fn, "w")
    f.write("Real_NHS_Number,Pseudonym_NHS_Number\n")
    for nhs_number in LOOKUP.keys():
        f.write("%d,%d" % (nhs_number, LOOKUP[nhs_number]) + "\n")


main()