Python Telegram weather radar bot

lambda_handler.py

from html.parser import HTMLParser
import http.client
from http.client import HTTPException
import json
import os
from urllib.parse import urljoin

SRI_HOST = "lietus.lv"
TELEGRAM_API_HOST = "api.telegram.org"


# We inherit from the base HTMLParser class and implement our custom handlers
class SRIHTMLParser(HTMLParser):
    data_list = []

    def handle_starttag(self, tag, attrs):
        pass

    def handle_endtag(self, tag):
        pass

    def handle_data(self, data):
        if '.png' in data:
            self.data_list.append(data)


def fetch_and_parse_sri_url():
    # Create an HTTP client (important - this time it is HTTP to match the target host)
    conn = http.client.HTTPConnection(host=SRI_HOST, timeout=5)
    # Instantiate our parser obj
    parser = SRIHTMLParser()
    endpoint = "/sri/"
    conn.request("GET", endpoint, "")
    res = conn.getresponse()
    # Check that status is ok
    if res.status == 200:
        # We read the response binary data, decode to str and feed into our parser
        data = res.read()
        html = data.decode('utf-8')
        parser.feed(html)
        parser.close()
        # We know that the img resource we need is first in the list, so we return that and strip any whitespace
        return parser.data_list[0].strip()
    else:
        raise HTTPException(f"Unexpected status from {SRI_HOST} : {res.status}")


def lambda_handler(_event, _context):

    # Create client connection with Telegram API
    conn = http.client.HTTPSConnection(TELEGRAM_API_HOST)

    telegram_token = os.getenv('TELEGRAM_TOKEN')
    # Check that token is not empty
    if telegram_token is not None:

        endpoint = f"/bot{telegram_token}/sendPhoto"

        sri_img_resource = fetch_and_parse_sri_url()

        payload = {
            'chat_id': -1001467903359,
            'photo': urljoin(f"http://{SRI_HOST}", f"sri/{sri_img_resource}"),
            'caption': 'Current radar image.'
        }

        headers = {'content-type': "application/json"}

        # Make a POST request
        conn.request("POST", endpoint, json.dumps(payload), headers)

        # Get the request response and save it
        res = conn.getresponse()

        return {
            'statusCode': res.status,
            'body': json.dumps('Lambda executed.')
        }
    else:
        raise EnvironmentError("Missing TELEGRAM_TOKEN env variable!")