Python 3 Text Processing with NLTK 3 Cookbook

Most of the time, the default sentence tokenizer will be sufficient

Once you have a custom sentence tokenizer, you can use it for your own corpora

The PunktSentenceTokenizer class uses an unsupervised learning algorithm to learn what constitutes a sentence break. It is unsupervised because you don't have to give it any labeled training data, just raw text

This difference is a good demonstration of why it can be useful to train your own sentence tokenizer, especially when your text isn't in the typical paragraph-sentence structure

tokenizer. You can get raw text either by reading in a file, or from an NLTK corpus using the raw() method