Question

tell me a good book for natural language processing in python, should be some introductory book ?

Answer 1

Umm, I know it's old, but you could check out this guy:
http://www.ibm.com/developerworks/linux/library/l-python5/index.html#author1

I'm sure you know
http://www.diveintopython.net

And this is mine, completely simple but still fun..
http://telliott99.blogspot.com/2009/07/python-for-simulations-5.html

Ultimately, any reason not to go here:
http://www.amazon.com/Natural-Language-Processing-Python-Steven/dp/0596516495
??

Answer 2

thanks ....