def grep(pattern, *files_or_paths):
    """Returns lines matched in fnames, where fnames can either be pathnames to
    files to grep through or open file objects to grep through line by line"""
    matches = []

    for fop in files_or_paths:
        with fileobj(fop) as fo:
            matches.extend((line for line in fo if re.match(pattern, line)))

    return matches