Open a csv, add a new column, concatenate information from various rows, insert desired concat into last cell in row

WikiMediaFileNamer.py

#!/usr/bin/python

import csv
import sys

filename = sys.argv[1]
# destination = sys.argv[2]

titles = []
met = " MET "
image_url = []
newfilename = ""

with open(filename) as csvinput:
    reader = csv.reader(csvinput)
    with open('output.csv', 'w') as csvoutput:
        writer = csv.writer(csvoutput, lineterminator='\n')
        reader = csv.reader(csvinput)

        all = []
        row = next(reader)
        row.append('Filename')
        all.append(row)

        for row in reader:
            newfilename = (row[7]) + met + (row[44].rsplit('/', 1)[-1])[:-4]
            # print newfilename
            row.append(newfilename)
            all.append(row)

        writer.writerows(all)