merge srt segment with given time interval

SrtSegmentMerger.py

#!/usr/bin/python3
# -*- coding: utf-8 -*-
"""
This is a Python program for merging subtitle files, which uses the third-party library "srt"(https://github.com/cdown/srt) to parse and compose srt files.
The basic idea of the program is to parse the original srt file into multiple "srt.Subtitle" objects, and then iterate and process these objects. 
For adjacent two subtitles, if the time interval between them is less than "MIN_TIME_INTERVALS" (defined in the program as the minimum time interval), they are merged into a new subtitle. 
Specifically, the content of the original subtitles is extracted and connected with "separator_operator" (defined in the program as the separator), 
and a new "srt.Subtitle" object is created with the new start and end times.

Finally, all the new "srt.Subtitle" objects are merged into a new srt file and output to standard output.
The program can be specified the path of the srt file to be processed via command line parameters. If no parameter is specified, the program will output instructions for use.
"""

import srt
import sys
MIN_TIME_INTERVALS = 20
separator_operator = '\n'

def run(filepath, min_time_intervals):  
    with open(filepath, 'r', encoding="utf-8") as f:
        lines = f.read()
        newsubs = []
        newsubs_index = 0
        subs = list(srt.parse(lines))
        start_time = subs[0].start
        start_idx = 0
        end_idx = 0
        subs_len = len(subs)

        for sub in subs:
            if (start_idx == -1):
                start_idx = sub.index
                start_time = sub.start
                continue

            if (sub.end - start_time).seconds < min_time_intervals and sub.index != subs[subs_len-1].index:
                continue

            # merge sub
            contents = []
            for i in range(start_idx, min(sub.index+1, subs_len)):
                contents.append(subs[i].content.strip())

            end_idx = sub.index
            new_sub = srt.Subtitle(index=newsubs_index, start=subs[start_idx].start, end=sub.end, content=separator_operator.join(contents))
            newsubs.append(new_sub)
            newsubs_index += 1
            start_idx = -1

        print(srt.compose(newsubs))

if __name__=='__main__':
    if len(sys.argv) == 1:
        print("usage: SrtSegmentMerger ${file_path}")
    else:
        filepath = sys.argv[1]
        run(filepath=filepath, min_time_intervals=MIN_TIME_INTERVALS)