punch holes in a file

hole_punch.py

from StringIO import StringIO 
import sys
import random


if len(sys.argv) != 3:
  print "usage:  hole_punch.py in_filename out_filenae"
  exit()

ifname = sys.argv[1]
ofname = sys.argv[2]

with open(ifname, 'rb') as f:
  d = StringIO(f.read())

l = d.len
percent = 0.1
holes = random.randint(0, int(d.len * percent))

for i in range(0, holes):
  d.seek( random.randint(0, d.len) )
  d.write('\x00')

d.seek(0)
with open(ofname, 'wb') as f:
  f.write(d.read())