345449.vhj5l3oj7.asia: PaperScissorsRock.py

Wed Dec 26 16:00:00 GMT 2001

PaperScissorsRock

#: c11:PaperScissorsRock.py
# Demonstration of multiple dispatching.
from __future__ import generators
import random

# An enumeration type:
class Outcome:
  def __init__(self, value, name): 
    self.value = value
    self.name = name
  def __str__(self): return self.name 
  def __eq__(self, other):
      return self.value == other.value

Outcome.WIN = Outcome(0, "win")
Outcome.LOSE = Outcome(1, "lose")
Outcome.DRAW = Outcome(2, "draw")

class Item(object):
  def __str__(self): 
    return self.__class__.__name__

class Paper(Item):
  def compete(self, item):
    # First dispatch: self was Paper
    return item.evalPaper(self)
  def evalPaper(self, item):
    # Item was Paper, we're in Paper
    return Outcome.DRAW
  def evalScissors(self, item):
    # Item was Scissors, we're in Paper
    return Outcome.WIN
  def evalRock(self, item):
    # Item was Rock, we're in Paper
    return Outcome.LOSE

class Scissors(Item):
  def compete(self, item): 
    # First dispatch: self was Scissors
    return item.evalScissors(self)
  def evalPaper(self, item):
    # Item was Paper, we're in Scissors
    return Outcome.LOSE
  def evalScissors(self, item):
    # Item was Scissors, we're in Scissors
    return Outcome.DRAW
  def evalRock(self, item):
    # Item was Rock, we're in Scissors
    return Outcome.WIN

class Rock(Item):
  def compete(self, item):
    # First dispatch: self was Rock
    return item.evalRock(self)
  def evalPaper(self, item):
    # Item was Paper, we're in Rock
    return Outcome.WIN
  def evalScissors(self, item):
    # Item was Scissors, we're in Rock
    return Outcome.LOSE
  def evalRock(self, item):
    # Item was Rock, we're in Rock
    return Outcome.DRAW

def match(item1, item2):
  print "%s <--> %s : %s" % (
    item1, item2, item1.compete(item2))

# Generate the items:
def itemPairGen(n):
  # Create a list of instances of all Items:
  Items = Item.__subclasses__()
  for i in range(n):
    yield (random.choice(Items)(), 
           random.choice(Items)())

for item1, item2 in itemPairGen(20):
  match(item1, item2)
#:~

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