Shapely - convert polygons to lines?

Given a shapefile with polygons, how do I convert the polygons to individual lines instead? I know how to do this in QGIS, but I'm looking for a Shapely function which does the same thing.

Answer

bugmenot123 is ok but I find easier use the boundary of the polygons. If you have a multipolygon or a polygon with holes the boundary returns a multilinestrig, if you have a polygon without holes the boundary returns a linestring.

Here is a simple example so you can see how it works:

import shapely
from shapely.geometry import MultiPolygon, Point

pol1 = MultiPolygon([Point(0, 0).buffer(2.0), Point(1, 1).buffer(2.0)])
pol2 = Point(7, 8).buffer(1.0)
pols = [pol1, pol2]

lines = []

for pol in pols:
    boundary = pol.boundary
    if boundary.type == 'MultiLineString':
        for line in boundary:
            lines.append(line)
    else:
        lines.append(line)

for line in lines:
    print line.wkt