from datetime import datetime


def find_todays_file(dir_list=None):
    """Identifies filename of most recent Sierra report"""
    fhdate = datetime.strftime(datetime.now(), '%Y%m%d')
    if dir_list is not None:
        # grab the latest file with date
        for fh in sorted(dir_list, reverse=True):
            if 'BookOpsQC.{}'.format(fhdate) in fh:
                    return fh
    return None