A simple script to read an edgelist CSV file (each row is "vertex1,vertex2,value") and write to another edgelist file only the rows with non-zero values.

cut_zeroes_from_edgelist.py

import csv
import sys

if __name__=="__main__":
    if len(sys.argv) < 3:
        print 'Syntax:'
        print 'python {0} edgelist.csv output.csv'.format(__file__)
        sys.exit(1)

    input_row_count, output_row_count = 0, 0
    input_filename, output_filename = sys.argv[1:3]
    with open(input_filename, 'rb') as input_file:
        with open(output_filename, 'wb') as output_file:
            csv_out = csv.writer(output_file)
            for row in csv.reader(input_file):
                input_row_count += 1
                if row[-1] != '0':
                   csv_out.writerow(row)
                   output_row_count += 1

    print 'Read {0} rows from {1}.'.format(input_row_count, input_filename)
    print 'Wrote {0} rows to {1}.'.format(output_row_count, output_filename)