Bots

Bots are software programs that combine requests, which are typically provided as text, with contextual data, such as geolocation and payment information, to appropriately handle the request and respond. Bots are often also called "chatbots", "assistants" or "agents."

Open source Slack bot examples

Limbo is an awesome Slack chatbot that provides a base for Python code that otherwise would require boilerplate to handle the Slack API events firehose.
python-rtmbot is the bot framework for building Slack bots with the Real Time Messaging (RTM) API over WebSockets.

Python-specific Bots resources

How to Buid an SMS Slack Bot is a tutorial on using SMS text messages to communicate with a Slack bot that can post and receive messages. The bot is a good base for a more complicated Slack bot that could use natural language processing or other more advanced parsing techniques. Either Python 2 or 3 can be used with the code which is also available on GitHub.
How to write a Slack bot in Python is a solid code tutorial for building your first bot on the Slack platform.
Dropbox open sourced their security Slack bot, which is built in Python. The bot converses with a user when backend systems detect strange behavior on one of their accounts to check if there has been a security breach.
Build a Slack Bot that Mimics Your Colleagues with Python is a humorous post that uses the markovify Markov Chains library to generate responses that are similar to ones other Slack users have said.
A Slack bot with Python’s 3.5 asyncio shows how to connect a bot to Slack via the web API using the Python 3 asyncio standard library.
Facebook-Message-Bot is an open source Facebook Messenger bot written in Python.

Additional Bots resources

Slack bot token leakage exposing business critical information is a detailed look at a search on GitHub for Slack tokens that are used mostly for bots but must be kept secret. Otherwise those tokens expose the entire Slack team's messaging to outside parties.
The Economist wrote a general piece on why bots look like they'll gain adoption in various market segments. The piece doesn't have much technical depth but it's a good overview of how some businesses are looking at the opportunity.
Bots won't replace apps is a fantastic piece by WeChat's product manager on how text-based bots alone typically do not provide a good user experience. Instead, chat apps with automated responses, user data and basic web browser functionality are what has allowed bot concepts to bloom in Asian markets. There's a lot of good information in this post to unpack.