def get_n_first(file_names, checksums, N_first):
    """
    Given a list of file_names and a list of checksums, returns the 'N_first'
    items from both lists as a zip object.

    :param file_names: list of file names
    :param checksums: list of sha256 checksums
    :param N_first: int or None. If None, all items are returned
    :return: zipped N_first first items of file_names and checksums
    """
    zipped = list(zip(file_names, checksums))
    N_first = int(N_first) if N_first is not None else len(file_names)
    zipped = zipped[:N_first]
    return zipped