import hashlib


def _get_md5_hex(src_file):
    """get md5 hext string of a file"""
    with open(src_file, 'rb') as fhandle:
        md5obj = hashlib.md5()
        while True:
            strtmp = fhandle.read(131072)  # read 128k
            if len(strtmp) <= 0:
                break
            md5obj.update(strtmp)
    return md5obj.hexdigest()