import os
import hashlib


def file_md5(file_name, block_size=2**20):
    if not os.path.isfile(file_name):
        return
    hash = hashlib.md5()
    with open(file_name, 'rb') as f:
        while True:
            b = f.read(block_size)
            if not b:
                break
            hash.update(b)
        return
 
 hash.hexdigest()


for root, dirs, files in os.walk("your_path"):
    for file in files:
        file_path = os.path.join(root, file)
        md5 = file_md5(file_path)
        print file_path, md5
        if md5:
            os.rename(file_path, os.path.join(root, md5))