The website, http://www.nltk.org, says mid 2011 in a very vague manner. I would like to start using NLTK however I have done a fair amount of work with Python 3.x and I don
There is a "2and3" branch in the main nltk repo - see https://github.com/nltk/nltk/tree/2and3
It appears to be getting updated regularly, although I haven't tried it myself.
There's a Python 3 branch:
https://github.com/nltk/nltk/tree/nltk-py3k
It's a transformation of the trunk and gets updated every so often to keep up with changes. You can check it out directly from git (instead of using the NLTK installation) and give it a shot.
git clone git://github.com/nltk/nltk.git nltk --branch nltk-py3k
I haven't used it personally, but I assume it works.
For those who got here wondering when will nltk support python3:
Good news, the NLTK 3.0 series (currently on alpha and in development since Jan 2013) now support Python 2.6, 2.7 and Python 3 (http://www.nltk.org/nltk3-alpha/), We'll probably see a stable release soon :)
And the book is also being updated for python3, available at: http://www.nltk.org/book3/
So, the official release was in September 2014, just to add closure to the question
Here's the alpha release: https://github.com/nltk/nltk3-alpha
Alternative NLP: TextBlob is fully Python 3. https://github.com/sloria/TextBlob
Tutorial: http://www.stevenloria.com/how-to-build-a-text-classification-system-with-python-and-textblob/