Converting PostGIS table to Shapefile in Python?

I want to convert a PostGIS table into a shapefile (without using pgsql2shp).

In order to create a geometry in the shapefile I have to give the Xmin,Ymin and Xmax,Ymax, and the geometry which I have in my PostGIS table is an irregularly shaped one (I can get the exterior using bounding box but that will include some extra area more than my area of ineterest). Is there any method by which I can get the task done?

I want to do the thing programmatically and using Python.