import hashlib


def md5sum(file_name, blocksize=65536):
    """
    Computes md5sum on a fileself.

    :param file_name: The name of the file on which to compute the md5sum.
    :param blocksize: Blocksize used to compute md5 sum (default: 65536)
    :return: Hexdigest of md5sum for file.
    """
    md5 = hashlib.md5()
    with open(file_name, "rb") as f:
        for block in iter(lambda: f.read(blocksize), b""):
            md5.update(block)
    return md5.hexdigest()