Proof of concept for story scripting in Python with coroutines.

storyyield.py

#!/usr/bin/python

##
# storyyield.py: Proof of concept for story scripting in Python with coroutines.
##
# (c) 2011 Christopher E. Granade (cgranade@cgranade.com).
# Licensed under GPL v3.
##

from __future__ import print_function

## STORY ELEMENTS ##

class StoryElement(object):
    pass

class DialogueLine(StoryElement):
    def __init__(self, speaker, content):
        self.speaker = speaker
        self.content = content

class DialogueChoice(StoryElement):
    def __init__(self, speaker, responses):
        self.speaker = speaker
        self.responses = responses

class Character(StoryElement):
    def __init__(self, name):
        self.name = name
        
    def say(self, what):
        return DialogueLine(self, what)
        
    def offer_choice(self, responses):
        return DialogueChoice(self, responses)
        
## MONKEY PATCHING FOR UI DISPLAY ##

# NOTE: This monkey patching would ideally be the glue between the story
#       support and the rest of the game engine.
#       By implementing via monkey patching, the glue can be replaced based
#       on the current need, such as with a basic GUI for allowing authors to
#       debug their stories without playing the full game.

# TODO: consider making a decorator to ease monkey-patching here.

def print_dialogue_line(self):
    print("%s:\t%s" % (self.speaker.name, self.content))

DialogueLine.handle = print_dialogue_line

def handle_dialogue_choice(self):
    print("Dialogue choice for %s:" % self.speaker.name)
    for idx in range(len(self.responses)):
        print("\t%d: %s" % (idx, self.responses[idx]))
        
    player_resp = raw_input(u"> ")
    return int(player_resp)
    
DialogueChoice.handle = handle_dialogue_choice
        
## STORY SCENES ##

# NOTE: Authors need only be concerned with this part of the file.

def scene_test():
    alice = Character("Alice")
    bob = Character("Bob")
    
    yield alice.say("Hello, Bob.")
    yield bob.say("That's supposed to be 'Hello, world', I think.")
    
    resp = yield alice.offer_choice(["Oh, yeah.", "I'm more creative than that!"])
    if resp == 0:
        yield bob.say("Keeping it traditional, K&R style. I love it.")
    else:
        yield bob.say("Next I know, you'll be telling me that you don't like pointers!")
    
    
## MAIN BLOCK ##    
    
if __name__ == "__main__":
    story_generator = scene_test()
    try:
        story_elem = story_generator.next()
        while True:
            retval = story_elem.handle()
            story_elem = story_generator.send(retval)
    except StopIteration:
        print("\nEnd of story!")