NLTK is a powerful Python library for computational linguistics and text classification. NLTK include about 50 corpora and lexical resources such as Wordnet. NLTK is the most used tool for natural language processing in Python. It includes powerful algorithms for text tokenization, parsing, semantic reasoning, and text classification. We can find a complete guide of NLTK from http://nltk.org/.
To install NLTK, we just need to download the executable file from the website for windows and use
easy_install in Linux distributions.
We may need to install PyYaml in order to use NLTK. We can download PyYaml from http://pyyaml.org/wiki/PyYAML.
NLTK defines four basic classifiers: