Appending to files

Is there any way in xbmcvfs.File to append to a file, instead of just reading and writing. I want to write some data to the file (while downloading), close the file and then append new data to the file at a later stage.

Does anyone know if this is possible? I’ve also noticed that some examples of the File constructor have a third Boolean parameter:

Code:
f = xbmcvfs.File(path, 'w', True);

Does anyone know what that parameter does? It is not documented anywhere.