The script converts the old QGIS symbol XML structure using the @ notation for sub-symbols into a nested XML DOM structure for proper import in newer versions of QGIS (i.e >=1.9)

symbol_nesting.py

"""
/***************************************************************************
                               symbol_nesting.py
                              -------------------
    begin                : 20-12-2012
    copyright            : (C) 2012 by Arunmozhi
    email                : aruntheguy at gmail dot com
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/

    The script cconverts the sold symbols XML structure using the @ notation
    to the new multiple nested XML structure.

"""
import sys
import codecs
from xml.dom.minidom import parse
from xml.dom.minidom import getDOMImplementation

def convertXMLStructure( filepath ):
    ''' The function converts the old XML into new XML with nesting'''
    indom = parse( filepath )
    impli = getDOMImplementation()
    outdom = impli.createDocument( None, "qgis_style", None )
    outsymdom = outdom.createElement("symbols")
    outdom.documentElement.setAttribute("version", "0")
    outdom.documentElement.appendChild( outsymdom )
    symbols = indom.getElementsByTagName( "symbol" )
    for symbol in symbols:
        symbol_name = symbol.getAttribute("name")
        if '@' not in symbol_name:
            # Skip the sub-symbols in first iteration
            outsymdom.appendChild( symbol )
    outsymbols = outsymdom.getElementsByTagName( "symbol" )
    # Now fix the sub-symbols
    for symbol in symbols:
        symbol_name = symbol.getAttribute("name")
        if '@' in symbol_name:
            parts = symbol_name.split('@')
            parent_name = parts[1]
            layerno = int(parts[2])
            # get the parent symbol and insert the sub-symbol in correct layer
            for sym in outsymbols:
                sym_name = sym.getAttribute("name")
                if sym_name == parent_name:
                    sym.getElementsByTagName( "layer" )[ layerno ].appendChild( symbol )
    rampdom = indom.getElementsByTagName("colorramps")[0]
    outdom.documentElement.appendChild(rampdom)
    opf = codecs.open( filepath+"new.xml", mode="w", encoding="utf-8")
    opf.write( outdom.toxml() )

if __name__ == "__main__":
    if len( sys.argv ) == 2:
        convertXMLStructure( sys.argv[1] )
    else:
        print "Usage: python symbol_nesting.py style_filename.xml"\
                "Output: A new file with name: style_filename.xmlnew.xml"