qgis - How would one get the end points of a polyline?

I am attempting to write a script to get the end points of a series polylines, and then use those end points to create a polygon. I'm not sure which tools to begin to use on this project.

I would prefer to use QGIS or even better a python script using open source tools.

Answer

It is easier with Fiona, more "Pythonic", and list slicing:

import fiona
with fiona.drivers():
   for line in fiona.open("some_shapefile.shp"):
         # print first and last point of every line
         print line['geometry']['coordinates'][0], line['geometry']['coordinates'][-1]

And with shapely:

from shapely.geometry import Point
for line in fiona.open("some_shapefile.shp"):
   print Point(line['geometry']['coordinates'][0]), Point(line['geometry']['coordinates'][-1])

And you can construct you polygon and save it with Fiona

New: using the suggestion of sgillies (boundary) with the shape function of shapely

from shapely.geometry import shape
for line in fiona.open("some_shapefile.shp"):
     print shape(line['geometry']).boundary[0], shape(line['geometry']).boundary[1]