This library allows you to generate random text using a Markov chain. It has a single class, MarkovBot, which can read text files of your choice. You can then make it generate random text. If you have a Twitter account, you can also make the bot automatically reply to tweets of your choice, and you can make it periocially tweet something.
Read this post. It'll tell you all about installing this library and its dependencies.
Note that the markovbot library supports Python 2.7 and Python 3.5; it will automagically detect your version, and then load the correct code.
The example.py script is really simple, and should be a good way to get you acquianted with the basics of the MarkovBot class.
Thanks to Kathleen Burkhardt (@kburk1997) for implementing support for Python 3.5.