Get VietJet flight data from reservation code

crawl_vj.py

# -*- coding: utf-8 -*-
from lxml import html
import requests


class VJCrawl():
    def __init__(self):
        self.s = requests.Session()
        self.url = 'https://flightstatus.vietjetair.com/?lang=vi'
        self.user_agent = ("Mozilla/5.0 (X11; Linux x86_64) "
                           "AppleWebKit/537.36 (KHTML, like Gecko) "
                           "Chrome/59.0.3071.115 Safari/537.36")

    def get_tokens(self):
        self.s.headers.update({'User-Agent': self.user_agent})
        response = self.s.get(self.url)
        tree = html.fromstring(response.content)
        di = {}
        di['__VIEWSTATE'] = tree.xpath('//*[@id="__VIEWSTATE"]/@value')[0]
        di['__VIEWSTATEGENERATOR'] = tree.xpath('//*[@id="__VIEWSTATEGENERATOR"]/@value')[0]
        di['__EVENTVALIDATION'] = tree.xpath('//*[@id="__EVENTVALIDATION"]/@value')[0]
        return di

    def get_flight_info(self, flight_code):
        token = self.get_tokens()
        token['ctl00$MainContent$ScriptManager'] = 'ctl00$MainContent$ScriptManager|ctl00$MainContent$buttonSearch'
        token['ctl00$ddlLanguges'] = 'vi'
        token['__EVENTTARGET'] = 'ctl00$MainContent$buttonSearch'
        token['__EVENTARGUMENT'] = ''
        token['__ASYNCPOST'] = 'true'
        token['ctl00$MainContent$txtReservationNumber'] = flight_code

        r = self.s.post(self.url, data=token, params={'lang': 'vi'})
        tree = html.fromstring(r.content)
        result = []
        for flight in tree.xpath('//*[@class="trRow"]'):
            result.append(flight.xpath('./td/text()'))

        return result

    def get_multiple_flight_info(self, flight_code_list):
        for code in flight_code_list:
            yield self.get_flight_info(code)


if __name__ == '__main__':
    v = VJCrawl()
    print(v.get_flight_info(55767987))
    for fl in v.get_multiple_flight_info(range(55767987, 55767997)):
        print(fl)

get_multiple_flight_info(range(55767987, 55767997))

cho mình hỏi flight_code này là gì nhỉ? lấy từ đâu?
Thanks bạn nhiều