w3.py

from Crypto.Hash import SHA256
import os


def myhash():
    file = open('./test.mp4', 'rb')
    size = os.path.getsize('./test.mp4')
    block_num = size/1024

    file.seek(block_num*1024)
    bs = file.read()
    ha = SHA256.new()
    ha.update(bs)
    hlast = ha.digest()

    while block_num > 0:
        file.seek((block_num-1)*1024)
        bs = file.read(1024)
        ha = SHA256.new()
        ha.update(bs+hlast)
        hlast = ha.digest()
        block_num -= 1

    print hlast.encode('hex')
    file.close()