Send simple message to Google Hangouts Chat bot using webhook

Question

I've set up a webhook in a chat room in my Google Hangouts Chat.

I can successfully run their example code, which generates a message from the bot associated with the webhook in the chat:

from httplib2 import Http
from json import dumps

#
# Hangouts Chat incoming webhook quickstart
#
def main():
    url = '<INCOMING-WEBHOOK-URL>'
    bot_message = {
        'text' : 'Hello from Python script!'}

    message_headers = { 'Content-Type': 'application/json; charset=UTF-8'}

    http_obj = Http()

    response = http_obj.request(
        uri=url,
        method='POST',
        headers=message_headers,
        body=dumps(bot_message),
    )

    print(response)

if __name__ == '__main__':
    main()

However, I wish to send this message using standard library packages, such as urllib.

But when I use urllib and run the below code, I get an urllib.error.HTTPError: HTTP Error 400: Bad Request. Why am I getting this error?

import json
import urllib.parse
import urllib.request


def main():
    # python 3.6

    url = '<INCOMING-WEBHOOK-URL>'
    bot_message = {'text': 'Hello from Python script!'}
    message_headers = {'Content-Type': 'application/json; charset=UTF-8'}

    url_encoded = urllib.parse.urlencode(bot_message)
    byte_encoded = url_encoded.encode('utf-8')
    req = urllib.request.Request(url=url, data=byte_encoded, headers=message_headers)
    response = urllib.request.urlopen(req)
    print(response.read())


if __name__ == '__main__':
    main()

Answer 1

The difference is in the body format. In the first version, you dump into json, while in the second you urlencode it.

replace

url_encoded = urllib.parse.urlencode(bot_message)
byte_encoded = url_encoded.encode('utf-8')

with

byte_encoded = json.dumps(bot_message).encode('utf-8')