text2sub

import time
import datetime

def parseMsg(text, time1):
    line = text.readline()
    if line == '':
        raise ValueError
    timeEnd = line.find(']')
    nameEnd = line.find(':', timeEnd)

    time2 = time.strptime(line[1:timeEnd], '%H:%M:%S')
    name = line[timeEnd+2:nameEnd]
    msg = line[nameEnd+2:]

    t2 = datetime.timedelta(seconds=time2.tm_sec, minutes=time2.tm_min, hours=time2.tm_hour) - datetime.timedelta(seconds=time1.tm_sec, minutes=time1.tm_min, hours=time1.tm_hour)
    return (t2, time2, name, msg)

text = open('text.txt', 'r')
sub = open('sub.srt', 'w')

startTime = time.strptime(text.readline()[:-1], '%H:%M:%S')

time1 = None
time2 = None
count = 1

t1,time1,name1,msg1 = parseMsg(text, startTime)

while 1:
    try:
        t2,time2,name2,msg2 = parseMsg(text, startTime)
    except ValueError:
        sub.write(str(count) + '\n')
        sub.write('0'+str(t1)+',000' + ' --> ' + '0'+str(t2+datetime.timedelta(seconds=10))+',000' + '\n')
        sub.write(name1 + ':')
        sub.write(msg1 + '\n\n')
        break

    sub.write(str(count) + '\n')
    sub.write('0'+str(t1)+',000' + ' --> ' + '0'+str(t2)+',000' + '\n')
    sub.write(name1 + ':')
    sub.write(msg1 + '\n')
    count += 1

    t1 = t2
    time1 = time2
    name1 = name2
    msg1 = msg2
text.close()
sub.close()