Slack

Creating a Slack App

To send messages to Slack channels or users, you first need to create a Slack App and configure an Incoming Webhook.

  1. Go to the Slack API Apps page.

  2. Click Create New App → From scratch.

  3. Choose a name and select your Slack workspace.

  4. In the app settings, navigate to Incoming Webhooks and enable them.

  5. Click Add New Webhook to Workspace and choose the channel you want to post to.

  6. Copy the Webhook URL — you’ll use this to send messages.

For more information, refer to the official Slack Webhook documentation.

Example Webhook URL

A typical Slack Webhook URL looks like this:

https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX

Keep this URL secret — it authenticates requests to your workspace.

Notification Implementation

Once you have your webhook URL, you can post messages to Slack using a simple HTTP POST request.

import polars as pl
import requests
import os
import json

SLACK_WEBHOOK_URL = os.environ["SLACK_WEBHOOK_URL"]

def send_slack_message(message, channel=None):
    payload = {
        "text": message
    }
    if channel:
        payload["channel"] = channel

    response = requests.post(SLACK_WEBHOOK_URL, data=json.dumps(payload), headers={"Content-Type": "application/json"})
    print(response.text)
    return response.json()


def transform():
    text = """
    ⚠️ *New Alert!*
    """
    response = send_slack_message(text)
    return pl.LazyFrame(response)

Example Message Formatting

Slack supports basic formatting using Markdown-like syntax:

  • *bold* → bold

  • _italic_ → italic

  • `code` → code

  • <https://example.com|Custom Link> → Custom Link

You can also include emojis and attachments for richer notifications.

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