md5 a large file

gistfile1.txt

import sys
from hashlib import md5
target = sys.argv[1]
csize = 4096
md5sum = md5()

with open(target, 'rb') as f:
    blocks = iter(lambda: f.read(csize), '')
    for block in blocks:
        md5sum.update(block)

    print md5sum.hexdigest()