The Transport API in bzrlib provides URL based access to network resources.

   >>> import os
   >>> import bzrlib.transport as transport
   >>> root = transport.get_transport("file:///")
   >>>

Each Transport instance represents a single logical directory.

   >>> dir = transport.get_transport(".")
   >>> dir.base == os.getcwdu() + '/'
   True

You can change directories via the clone method:

   >>> parent = dir.clone('..')
   >>> parent.base == os.path.dirname(os.getcwdu()) + '/'
   True