Help with inverted dictionary

I'm new to Python and I'm struggling. I have a text file (*.txt) with
a couple thousand entries, each on their own line (similar to a phone
book). How do I make a script to create something like an inverted
dictionary that will allow me to call "robert" and create a new text
file of all of the lines that contain "robert"?

Thanks so much.
Received on Thu Sep 29 16:54:09 2005