[Edu-sig] simula.run(40) error

[reavey]

errors running your simulation program.
python 2.2
if I run 4 ticks no problem I tried 400 ticks went out around 11 and died.
--- Tick 2 -------
Duck6 gets eaten by Wolf1
Duck6 dies
Wolf2 gives birth
Wolf3 is born
Duck4 gives birth
Duck7 is born
Duck5 goes hungry
Bug4 goes hungry
Bug5 dies
Bug2 dies
Duck6 dies
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "simula.py", line 16, in run
    i.randevent()
  File "simula.py", line 76, in randevent
    else:            self.dies()  # ... or die
  File "simula.py", line 49, in dies
    del creatures[self.name]  # Goodbye World!
KeyError: Duck6


I like your program.
beautiful idea. what is this error?
thanks
re-v