Make a vlc playlist for a directory

playlist.py

from xml.dom.minidom import Document
import os
import sys

validExt = ('.avi') #only add files with these extensions to the playlist

if(len(sys.argv) > 1):
    rootdir = sys.argv[1]+'/'
    print(sys.argv[1])
else:
    rootdir = os.getcwd()+'/'

def createTrack(file, path):
    track = doc.createElement("track")
    tracklist.appendChild(track)
    location = doc.createElement("location")
    locationText = doc.createTextNode('file:///'+path+file)
    location.appendChild(locationText)
    track.appendChild(location)

doc = Document()
playlist = doc.createElement("playlist")
playlist.setAttribute("version","1")
playlist.setAttribute("xmlns","http://xspf.org/ns/0/")
playlist.setAttribute("xmlns:vlc","http://www.videolan.org/vlc/playlist/ns/0/")
doc.appendChild(playlist)
title = doc.createElement("title")
titlet = doc.createTextNode("Playlist")
title.appendChild(titlet)
playlist.appendChild(title)
tracklist = doc.createElement("trackList")
playlist.appendChild(tracklist);

for subdir, dirs, files in os.walk(rootdir):
    for file in files:
        ext = os.path.splitext(file)
        if(ext[1] in validExt):
            createTrack(file, subdir)

f = open(rootdir+"playlist.xspf",'w')
f.write(doc.toxml())
f.close()