Python3系でSlackにメッセージをポストするサンプル

slack-post.py

import os
import urllib.request, urllib.parse

MESSAGE = 'sample message.'
POST_SLACK_TOKEN_ID = os.environ.get('POST_SLACK_TOKEN_ID')
POST_SLACK_CHANNEL_ID = os.environ.get('POST_SLACK_CHANNEL_ID')

URL = 'https://slack.com/api/chat.postMessage'
headers = {
    'Authorization': 'Bearer ' + POST_SLACK_TOKEN_ID
}
message = {
    'text' : MESSAGE,
    'channel' : POST_SLACK_CHANNEL_ID
}
data = urllib.parse.urlencode(message).encode()
req = urllib.request.Request(URL,data=data,headers=headers,method='POST')
urllib.request.urlopen(req)