National rail FTP timetable downloader

ftp.py

    import xml.etree.cElementTree as ET
    from ftplib import FTP
    import StringIO
    import gzip
    import time
    import re
    import json
    import boto3
    import tempfile

    client = boto3.client('s3')
    s3 = boto3.resource('s3')

    resp = client.get_object(Bucket = 'tv-private', Key = 'national-rail-ftp.txt')
    password = resp["Body"].read().decode('utf-8')

    ftp = FTP('datafeeds.nationalrail.co.uk')
    ftp.login(user = 'ftpuser', passwd=password)
        
    files = []
    ftp.retrlines('NLST', files.append)
    filename = next(f for f in files if f.endswith('v8.xml.gz'))

    timetable_gz = tempfile.TemporaryFile()
    ftp.retrbinary('RETR ' + filename, timetable_gz.write)

    timetable_gz.seek(0)
    timetable = gzip.GzipFile(fileobj = timetable_gz, mode = 'rb')

    tofind = [
        'BCKNHMJ <- 08:32',
        'BCKNHMJ -> 08:41',
        'BCKNHMJ <- 08:19'
    ]

    ids = []
    for (e, elem) in ET.iterparse(timetable):
        if(elem.tag.endswith('Journey')):
            children = list(elem)

            (start, departs) = (children[0].get('tpl'), children[0].get('ptd'))
            (end, arrives) = (children[-1].get('tpl'), children[-1].get('pta'))

            if(start and end and departs and arrives):
                skey = start + ' -> ' + departs
                dkey = end + ' <- ' + arrives
                if (skey in tofind or dkey in tofind):
                    ids.append(elem.get('uid'))

            elem.clear()

    s3.Object('tv-timetables', 'trains.json').put(Body=json.dumps(ids))
    timetable_gz.close()
    timetable.close()