Vishwadeep1 0 Newbie Poster

Hello.
I am working in QGIS software in which backend python programming is used. I want to interesect a polygon with different lines passing through it, and find the width of that polygon in QGIS 1.8. The polygon is a shapefile ie .shp file.
So please help me to complete this job. Intersect polygon with lines and find the width of that rectangles or any other polygon.