Extract sbix strikes from font

extractSbixImages.py

#!/usr/bin/env python
from fontTools.ttLib import TTFont
from os.path import exists, join
from os import mkdir, sys

# print 'Number of arguments:', len(sys.argv), 'arguments.'
# print 'Argument List:', str(sys.argv)
# print sys.argv[1]

def main():
	f = TTFont(sys.argv[1])

	if f.has_key("sbix"):
		sbix = f["sbix"]
		# print vars(sbix)

		for bs in sbix.strikes.itervalues():
			# print vars(bs), "\n"
			print "Extracting ppem:", bs.ppem, "- Resolution:", bs.resolution

			setpath = join("extracted", "set_%i" % bs.ppem)
			if not exists(setpath):
				mkdir(setpath)

			print "Writing bitmap set to <%s>" % setpath

			for bm in bs.glyphs.itervalues():
				# print vars(bm), "\n"
				if bm.graphicType is not None:
					filename = join(setpath, "%s.png" % bm.glyphName)
					pf = file(filename, "wb")
					pf.write(bm.imageData)
					pf.close()
	else:
		print "Font has no sbix table."

if __name__ == "__main__":
	main()

It's great. But how can I naming png file by code points?