core-agent-linux/qubes-rpc/xdg-icon

#!/usr/bin/python2
import xdg.IconTheme
import sys
import os

themes = ['Humanity', 'Adwaita', 'gnome', 'oxygen']
themes = themes + sorted([d for d in os.listdir("/usr/share/icons") if d not in themes and os.path.isdir("/usr/share/icons/" + d)])

if len(sys.argv) < 3:
	print "Usage:", sys.argv[0], "ICON SIZE"
	sys.exit(1)

for theme in themes:
	icon = xdg.IconTheme.getIconPath(sys.argv[1], theme = theme, size = int(sys.argv[2]))
	if icon is not None:
		break

if icon is None:
	sys.exit(1)

print icon