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.

Create a new app

Go to the Slack API Apps page and click Create New App → From scratch.

Name and workspace

Choose a name for the app and select the Slack workspace where it will be installed.

Enable Incoming Webhooks

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

Add a webhook to a channel

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

Copy the webhook URL

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

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

Caution

Keep the webhook URL secret — it authenticates requests to your workspace.

Example Webhook URL

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

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

Formatting and examples

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.