Sort python log files using date time. Takes datetime regex as input

sort_log.py

import argparse
import re
from datetime import datetime
from signal import signal, SIGPIPE, SIG_DFL
from operator import itemgetter

signal(SIGPIPE, SIG_DFL)


def test_sorted_lines():
    input_log_1 = ["2019-05-08 08:44:21,159 : 1 line 1",
                   "2019-05-08 08:44:22,996 : 1 line 2",
                   "line 2.1",
                   "line 2.2",
                   "2019-05-08 08:44:27,000 : 1 line 3", ]
    input_log_2 = ["2019-05-08 08:44:21,158 : 2 line 1",
                   "2019-05-08 08:44:22,995 : 2 line 2",
                   "2019-05-08 08:44:26,000 : 2 line 3",
                   "line 3.1",
                   "line 3.2", ]

    input_log_3 = ["line 0.1",
                   "line 0.2",
                   "line 0.3",
                   "2019-05-08 08:45:00,000 : 3 line 2",
                   "2019-05-08 08:46:00,000 : 3 line 3", ]

    expected_output = [
        "2019-05-08 08:44:21,158 : 2 line 1",
        "2019-05-08 08:44:21,159 : 1 line 1",
        "2019-05-08 08:44:22,995 : 2 line 2",
        "2019-05-08 08:44:22,996 : 1 line 2\nline 2.1\nline 2.2",
        "2019-05-08 08:44:26,000 : 2 line 3\nline 3.1\nline 3.2",
        "2019-05-08 08:44:27,000 : 1 line 3",
        "2019-05-08 08:45:00,000 : 3 line 2",
        "2019-05-08 08:46:00,000 : 3 line 3",
    ]

    output = list(sorted_lines([input_log_2, input_log_1, input_log_3], re.compile('(%s)' % r'^[\d :-]{19},\d+')))

    assert output == expected_output


def get_datetime(asctime):
    return datetime.strptime(asctime, "%Y-%m-%d %H:%M:%S,%f")


def parse_args():
    parser = argparse.ArgumentParser()
    parser.add_argument('-p', '--pattern', help='datetime pattern',
                        default=r'^[\d :-]{19},\d+')
    parser.add_argument('log', nargs='+', type=argparse.FileType(), help="log files")
    return parser.parse_args()


def rows(f, datetime_pattern):
    non_match = 0
    last_row = ()
    for line_no, raw_line in enumerate(f, 1):
        line = raw_line.rstrip()
        match = datetime_pattern.search(line)
        if match:
            if last_row:
                yield last_row
            last_row = [match.group(1), line]
        else:
            non_match += 1
            if last_row != ():
                # only do it if last row had something
                last_row[1] = last_row[1] + "\n" + line
    else:
        if last_row:
            yield last_row


def print_formatted(start, end):
    duration = end['time'] - start['time']
    print("%s\t%0.03f" % (end['time'].strftime("%Y-%m-%d %H:%M:%S.%f"), duration.total_seconds()))


def indexed_rows(files, pattern):
    for f in files:
        for indexed_row in rows(f, pattern):
            yield indexed_row


def sorted_lines(files, pattern):
    for _, line in sorted(indexed_rows(files, pattern), key=itemgetter(0)):
        yield line


def main():
    args = parse_args()
    datetime_pattern = re.compile('(%s)' % args.pattern)
    for line in sorted_lines(args.log, datetime_pattern):
        print(line)


if __name__ == '__main__':
    main()