gistfile1.py

from overviewer_core.observer import Observer
import os

class AnnouncingObserver(Observer):
    def __init__(self):
        self.handle = open('/full/path/to/input_command', 'w')
        super(AnnouncingObserver,self).__init__()

    def finish(self):
        self.handle.write("say Rendered %d of %d. %d%% complete\n" % (self.get_max_value(), self.get_max_value(), 100.0))
        self.handle.flush()
        super(AnnouncingObserver, self).finish()
        self.handle.close()

    def update(self, current_value):
        super(AnnouncingObserver, self).update(current_value)
        if self._need_update():
            self.handle.write("say Rendered %d of %d. %d%% complete\n" % (self.get_current_value(), self.get_max_value(), self.get_percentage()))
            self.handle.flush()
            self.last_update = current_value
            return True
        return False
    
    def _need_update(self):
        return (self.get_current_value() * 100.0 / self.get_max_value()) - (self.last_update * 100.0 / self.get_max_value()) >= 20.0