PyCon UK 2017 Schedule to iCalendar script

pyconical.py

#!/usr/bin/env python3

import re
import sys
import os
import os.path
import begin
import icalendar
import yaml
import pytz
from datetime import date, datetime, timedelta


@begin.start
def main(sitepath: "Path to website source",
         output: "File to write iCalendar to"='pyconuk2017.ics',
         website: "URL of online website to link to"='http://2017.pyconuk.org'):
    """Creates ical data from the schedule data in the PyConUK website source"""

    schedpath = os.path.join(sitepath, 'schedule')
    sesspath = os.path.join(sitepath, 'sessions')
    tz = pytz.timezone('Europe/London')
    now = datetime.now(tz=tz)
    cal = icalendar.Calendar()
    cal.add('prodid', '-//pyconical.py//Mark Frimston//')
    cal.add('version', '2.0')
        
    for day in os.listdir(schedpath):
        daydate = int(re.sub(r'\D', '', day))        
        daypath = os.path.join(schedpath, day)
        
        for room in os.listdir(daypath):
            roompath = os.path.join(daypath, room)
            
            for time in os.listdir(roompath):
                hour,minute = map(int,time.split(':'))

                with open(os.path.join(roompath,time),'r') as f:
                    slotdata = yaml.load(f)

                ev = icalendar.Event()
                ev.add('uid', 'pcuk17-{}-{}-{}-{}'.format(room.lower().replace(' ',''), 
                                                          daydate, hour, minute))
                ev.add('dtstart', datetime(2017, 10, daydate, hour, minute, 0, tzinfo=tz))
                ev.add('duration', timedelta(0, 60*30))
                ev.add('dtstamp', now)
                ev.add('location', room)
                
                title = slotdata.get('title', None)
                session = slotdata.get('session', None)

                if title:
                
                    ev.add('summary', title)
                    ev.add('categories', ['non-session'])
                    
                elif session:
                
                    with open(os.path.join(sesspath, '{}.md'.format(session)), 'r') as f:
                        sessdata = next(yaml.load_all(f))
                        f.seek(0)
                        desc = re.sub(r'^.*?---\n','',f.read(), flags=re.DOTALL)
                    stype, sname = session.split('/')
                    title = '[{}] {}'.format(stype, sessdata.get('title', None))
                    subtitle = sessdata.get('subtitle', None)
                    if subtitle: title += ': {}'.format(subtitle)
                    cats = [stype]
                    track = sessdata.get('track', None)
                    if track: cats.append(track)
                    ev.add('summary', title)
                    ev.set_inline('categories', cats)
                    ev.add('description', desc)
                    ev.add('url', '{}/sessions/{}/{}'.format(website, stype+'s', sname))
                    
                cal.add_component(ev)

    with open(output, 'wb') as f:
        f.write(cal.to_ical())