mudar o tamanho da fonte de um gtk.TextView.

import gtk
import pango
 
window = gtk.Window()
textview = gtk.TextView()
textview.set_size_request(300,300)
font = pango.FontDescription("Arial 20")
textview.modify_font(font)
window.add(textview)
window.set_size_request(200,200)
window.set_position(gtk.WIN_POS_CENTER)
window.show_all()

gtk.main()