How to design a search engine in Python?

[subhabangalore at gmail.com]

Dear Group, 

I am trying to build a search engine in Python. 

To do this, I have read tutorials and working methodologies from web and books like Stanford IR book [ http://www-nlp.stanford.edu/IR-book/]. I know how to design a crawler, I know PostgresSql, I am fluent with PageRank, TF-IDF, Zipf's law, etc. 
I came to know of Whoosh[https://pypi.python.org/pypi/Whoosh/]

But I am looking for a total tutorial how to implement it. If any body may kindly direct me. 

I heard there are good source codes and prototypes, but I am not getting. 

Apology if this is not a question of the room. I tried to post as this is a room of Python bigwigs. 

Regards,
Subhabrata.