خالد حسني أَنَا الّذِي نَظَرَ الأَعْمَى إِلَى أَدَبِي وَأَسْمَعَتْ كَلِمَاتِي مَنْ بِهِ صَمَمُ

I was trying to figure how to list fonts accessible to GTK (or pango actually), it turned out that pango.Context has a list_families() method that returns a tuple of pango.FontFamily objects.
Some thing like this:

window = gtk.Window()
context = window.get_pango_context()
families = context.list_families()

for i in families:
        print i.get_name()