Fix time format in SubRip srt subtitle files

fixSrtTimeFormat.py

#!/usr/bin/env python3
import re, sys
from pathlib import Path


def fix_srt_time_format(sub_file_name: str):
    """Fix time format in SubRip srt subtitle files.
    This script will:
      * replace `.` delimiter between seconds and miliseconds with expected `,`
      * replace leading `0:` in timestamps with expected `00:`

    For reference please see: https://en.wikipedia.org/wiki/SubRip
    """
    if not sub_file_name.endswith(".srt"):
        return
    file_path = Path(sub_file_name)
    with open(file_path, "r") as sub_file_handle:
        with open(f"{file_path.stem}.fixed.srt", "w", encoding="UTF-8") as fixed_sub_file_handle:
            for line in sub_file_handle.readlines():
                if re.match(".*-->.*", line):
                    start, end = line.split(" --> ")
                    if "." in start:
                        start = re.sub("\.", ",", start)
                        end = re.sub("\.", ",", end)
                    if start.startswith("0:"):
                        start = re.sub("^0:", "00:", start)
                        end = re.sub("^0:", "00:", end)
                    new_line = f"{start} --> {end}"
                    fixed_sub_file_handle.write(new_line)
                else:
                    fixed_sub_file_handle.write(line)


for file_name in sys.argv[1:]:
    fix_srt_time_format(Path(file_name))

This script can be executed as a standalone script or can be executed from Nautilus (Gnome's GUI file manager) by right-clicking on a subtitle file.
To make if available in Nautilus' righ-click menu, simply save this script in /home/${USER}/.local/share/nautilus/scripts/ and make it executable chmod +x fixSrtTimeFormat.py.