Slack Events API Python Adapter

3.0.3 verified Fri May 01 auth: no python

A Python adapter for the Slack Events API, built on Flask. It handles event verification, parsing, and dispatching for incoming Slack events. The current version is 3.0.3, requiring Python >=3.6 and Flask 2.x. Releases are irregular as the library is in maintenance mode.

pip install slackeventsapi

Common errors

error ImportError: cannot import name 'SlackEventAdapter' from 'slackeventsapi' ↓

cause The package is installed but not correctly imported; or version does not export that name.

fix

Run: pip uninstall slackeventsapi && pip install slackeventsapi. If still fails, check the package version: import slackeventsapi; print(slackeventsapi.__version__)

error TypeError: __init__() missing 1 required positional argument: 'signing_secret' ↓

cause The first argument to SlackEventAdapter is now signing_secret (required in v2.0+).

fix

Pass your Slack app's signing secret: SlackEventAdapter('your_signing_secret', '/events', app)

error slackeventsapi.exceptions.SlackRequestVerificationFailed: Invalid request signature ↓

cause Request signature verification failed. Usually due to misconfigured signing_secret or clock drift.

fix

Double-check SLACK_SIGNING_SECRET environment variable. Ensure server time is accurate (NTP). If behind a proxy, forward original headers.

error Challenges are not matched and the URL verification fails ↓

cause The event URL verification endpoint returns unexpected body or status code.

fix

Ensure your route returns a plain text response with the challenge value. Using SlackEventAdapter automatically handles it.

Warnings

breaking In v3.0.0, dropped support for Python 2.7 and Flask 1.x. Ensure your environment uses Python >=3.6 and Flask >=2.0. ↓

fix Upgrade Python to 3.6+ and Flask to 2.x.

deprecated The library is in maintenance mode; no new features are planned. Slack recommends using Bolt for Python (slack_bolt) for new projects. ↓

fix Migrate to slack_bolt: https://github.com/slackapi/bolt-python

gotcha Event acknowledgements must be sent within 3 seconds. Long-running handler blocks the response; use threads or async to avoid timeout. ↓

fix Offload processing to a background thread or queue. See GitHub issue #84.

breaking In v2.0.0, switched from Verification Token to Signing Secret. Old code using Verification Token will fail. ↓

fix Update your app to use Signing Secret from Slack app settings. Pass signing_secret instead of verification_token.

Imports

SlackEventAdapter

from slackeventsapi import SlackEventAdapter

verify_signature

from slackeventsapi import verify_signature

Quickstart

Minimal Flask app using SlackEventAdapter to respond to app_mention events.

import os
from flask import Flask
from slackeventsapi import SlackEventAdapter

app = Flask(__name__)
slack_signing_secret = os.environ.get('SLACK_SIGNING_SECRET', '')
slack_events_adapter = SlackEventAdapter(slack_signing_secret, "/slack/events", app)

@slack_events_adapter.on("app_mention")
def handle_app_mention(event_data):
    print("App mentioned:", event_data)
    return "OK"

if __name__ == "__main__":
    app.run(port=3000)