Generate a chapters file for `mp4chaps` from `.mp3` files in the current directory or the one passed as its first argument.

gen_audiobook_chapters.py

# -*- coding: utf-8 -*-
import sys, re

from datetime import timedelta
from os import listdir, getcwd
from os.path import isfile, join
from mutagen.mp3 import MP3

EXTENSION = ".mp3"
# RE to extract chapter names (name being the first capture group.)
REGEX = r'Chapter \d{1,2} - (.+)(' + EXTENSION + ')'
# REGEX = r'CH\d{2}(.+)(' + EXTENSION + ')'

try:
    directory = sys.argv[1]
except IndexError:
    directory = getcwd()

result = ""

def get_dir_files(path):
    return sorted(filter(lambda x: isfile(join(path, x)), listdir(path)))

def get_dir_files_with_ext(path, ext):
    files = get_dir_files(path)
    return filter(lambda x: True if ext in x else False, get_dir_files(path))

running_total = timedelta(seconds=0)
for i, file in enumerate(get_dir_files_with_ext(directory, EXTENSION), start=1):
    chapter_name = re.sub(REGEX, r'\1', file)
    hours = running_total / timedelta(hours=1) # done so to support files longer than 24 hours
    msms = str(running_total % timedelta(hours=1))[2:]
    file_length = timedelta(seconds=MP3(file).info.length)
    result += "%d:%s Chapter %d\n" % (hours, msms, i)
    running_total += file_length

result = re.sub(r'^(\d{1}):', r'0\1:', result, flags=re.MULTILINE)
result = re.sub(r'(\.\d{3})\d{3}', r'\1', result, flags=re.MULTILINE)
result = re.sub(r'(\d{2}:\d{2}:\d{2}) ', r'\1.000 ', result, flags=re.MULTILINE)

print(result)