eventreactor.py

import heapq

class EventReactor(object):
  """Processes a set of EventStream and executes their events in order."""
  def __init__(self):
    self.time = 0.0 # Current time
    self.events = [] # Holds (time, event function, stream) tuples in a heapq

  def add_stream(self, stream):
    """Adds an event stream to the reactor.
    
    Args:
      stream: An iterator that returns (interval, function) tuples.
    """
    first_time, first_func = stream.next()
    first_time += self.time
    heapq.heappush(self.events, (first_time, first_func, stream))

  def run(self):
    """Executes events until all the streams are exhausted."""
    while self.events:
      # Fetch the next event and execute it
      new_time, func, stream = heapq.heappop(self.events)
      self.time = new_time
      func()
      # Get the next event from this stream, if one exists, and add it back
      try:
        next_time, next_func = stream.next()
        next_time += self.time
        heapq.heappush(self.events, (next_time, next_func, stream))
      except StopIteration:
        pass