run usearch

def usearch5(query, db, type, out, threads = '4', evalue = '100', alignment = 'local'):
    """
    run usearch
    """
    if os.path.exists(out) is False:
        print('# ... running usearch with %s as query and %s as database' % (query, db))
        if type[1] == 'nucl':
            threads = ''
        else:
            threads = '-threads %s' % (threads)
        os.system('usearch \
                -query %s -%s %s -blast6out %s \
                -evalue %s %s -%s >> log.txt' \
                % (query, type[0], db, out, evalue, threads, alignment))
    else:
        print('# ... usearch output found for %s as query and %s as database' % (query, db))