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# Slack Events API
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Python adapter for receiving and parsing events from Slack's Events API using Flask. This library provides an event-driven approach to building Slack applications by allowing developers to attach functions to event listeners, handling authentication, signature verification, and HTTP request processing automatically.
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## Package Information
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- **Package Name**: slackeventsapi
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- **Language**: Python
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- **Installation**: `pip install slackeventsapi`
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## Core Imports
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```python
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from slackeventsapi import SlackEventAdapter
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```
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For exceptions:
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```python
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from slackeventsapi.server import SlackEventAdapterException
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```
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For version information:
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```python
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from slackeventsapi.version import __version__
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```
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For direct SlackServer access (advanced usage):
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```python
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from slackeventsapi.server import SlackServer
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```
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## Basic Usage
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```python
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import os
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from slackeventsapi import SlackEventAdapter
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# Create the adapter with your Slack app's signing secret
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slack_signing_secret = os.environ["SLACK_SIGNING_SECRET"]
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slack_events_adapter = SlackEventAdapter(slack_signing_secret, "/slack/events")
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# Listen for "reaction_added" events
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@slack_events_adapter.on("reaction_added")
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def reaction_added(event_data):
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    event = event_data["event"]
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    emoji = event["reaction"]
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    print(f"Reaction added: {emoji}")
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# Listen for error events
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@slack_events_adapter.on("error")
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def error_handler(err):
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    print(f"ERROR: {err}")
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# Start the built-in Flask server
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slack_events_adapter.start(port=3000)
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```
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## Architecture
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The SlackEventAdapter integrates Flask web server capabilities with PyEE event emitter functionality:
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- **SlackEventAdapter**: Main class inheriting from BaseEventEmitter, providing the public API for event registration and server management
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- **SlackServer**: Internal Flask server handling HTTP requests, signature verification, and Slack protocol compliance
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- **Event Processing**: Automatic parsing of Slack event payloads and emission to registered listeners
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- **Security**: Built-in HMAC-SHA256 signature verification and timestamp validation to prevent replay attacks
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## Capabilities
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### Event Adapter
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Core functionality for creating and managing Slack event adapters, including initialization, server binding, and lifecycle management.
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```python { .api }
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class SlackEventAdapter(BaseEventEmitter):
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    def __init__(self, signing_secret, endpoint="/slack/events", server=None, **kwargs): ...
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    def start(self, host='127.0.0.1', port=None, debug=False, **kwargs): ...
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    # Public attributes
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    signing_secret: str  # The signing secret used for request verification
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    server: SlackServer  # The internal SlackServer instance
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```
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[Event Adapter](./event-adapter.md)
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### Event Handling
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Event listener registration and management using PyEE's event emitter pattern for processing various Slack event types.
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```python { .api }
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def on(self, event_type: str, callback: callable): ...
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def emit(self, event_type: str, *args): ...
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```
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[Event Handling](./event-handling.md)
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### Server Integration
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Integration with existing Flask applications and Blueprint-based architectures for incorporating Slack event handling into larger web applications.
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```python { .api }
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class SlackServer(Flask):
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    def __init__(self, signing_secret, endpoint, emitter, server): ...
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    def bind_route(self, server): ...
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    # Public attributes (accessible via adapter.server)
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    signing_secret: str  # The signing secret for request verification
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    emitter: SlackEventAdapter  # The parent event adapter instance
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    endpoint: str  # The URL endpoint for receiving events
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    package_info: str  # User-agent string with version information
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```
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[Server Integration](./server-integration.md)
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## Types
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```python { .api }
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class SlackEventAdapterException(Exception):
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    """Base exception for all errors raised by the SlackClient library"""
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    def __init__(self, msg=None): ...
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```
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## Constants
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```python { .api }
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__version__: str = "3.0.3"  # from slackeventsapi.version
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```