carfield.com.hk

Adapter.py

2001-12-26T16:00:00Z

#: c07:Adapter.py
# Variations on the Adapter pattern.

class WhatIHave:
  def g(self): pass
  def h(self): pass

class WhatIWant:
  def f(self): pass

class ProxyAdapter(WhatIWant):
  def __init__(self, whatIHave):
    self.whatIHave = whatIHave

  def f(self):
    # Implement behavior using 
    # methods in WhatIHave:
    self.whatIHave.g()
    self.whatIHave.h()

class WhatIUse:
  def op(self, whatIWant):
    whatIWant.f()

# Approach 2: build adapter use into op():
class WhatIUse2(WhatIUse):
  def op(self, whatIHave):
    ProxyAdapter(whatIHave).f()

# Approach 3: build adapter into WhatIHave:
class WhatIHave2(WhatIHave, WhatIWant):
  def f(self):
    self.g()
    self.h()

# Approach 4: use an inner class:
class WhatIHave3(WhatIHave):
  class InnerAdapter(WhatIWant):
    def __init__(self, outer):
      self.outer = outer
    def f(self):
      self.outer.g()
      self.outer.h()

  def whatIWant(self): 
    return WhatIHave3.InnerAdapter(self)

whatIUse = WhatIUse()
whatIHave = WhatIHave()
adapt= ProxyAdapter(whatIHave)
whatIUse2 = WhatIUse2()
whatIHave2 = WhatIHave2()
whatIHave3 = WhatIHave3()
whatIUse.op(adapt)
# Approach 2:
whatIUse2.op(whatIHave)
# Approach 3:
whatIUse.op(whatIHave2)
# Approach 4:
whatIUse.op(whatIHave3.whatIWant())
#:~

ChainOfResponsibility.py

2001-12-26T16:00:00Z

#: c06:ChainOfResponsibility.py

# Carry the information into the strategy:
class Messenger: pass

# The Result object carries the result data and
# whether the strategy was successful:
class Result:
  def __init__(self):
    self.succeeded = 0
  def isSuccessful(self): 
    return self.succeeded 
  def setSuccessful(self, succeeded): 
    self.succeeded = succeeded

class Strategy:
  def __call__(messenger): pass
  def __str__(self): 
    return "Trying " + self.__class__.__name__ \
      + " algorithm"

# Manage the movement through the chain and
# find a successful result:
class ChainLink:
  def __init__(self, chain, strategy):
    self.strategy = strategy
    self.chain = chain
    self.chain.append(self)

  def next(self):
    # Where this link is in the chain:
    location = self.chain.index(self)
    if not self.end():
      return self.chain[location + 1]

  def end(self):
    return (self.chain.index(self) + 1 >= 
            len(self.chain))

  def __call__(self, messenger):
    r = self.strategy(messenger)
    if r.isSuccessful() or self.end(): return r
    return self.next()(messenger)

# For this example, the Messenger
# and Result can be the same type:
class LineData(Result, Messenger):
  def __init__(self, data):
    self.data = data
  def __str__(self): return `self.data`

class LeastSquares(Strategy):
  def __call__(self, messenger):
    print self
    linedata = messenger
    # [ Actual test/calculation here ]
    result = LineData([1.1, 2.2]) # Dummy data
    result.setSuccessful(0)
    return result

class NewtonsMethod(Strategy):
  def __call__(self, messenger):
    print self
    linedata = messenger
    # [ Actual test/calculation here ]
    result = LineData([3.3, 4.4]) # Dummy data
    result.setSuccessful(0)
    return result

class Bisection(Strategy):
  def __call__(self, messenger):
    print self
    linedata = messenger
    # [ Actual test/calculation here ]
    result = LineData([5.5, 6.6]) # Dummy data
    result.setSuccessful(1)
    return result

class ConjugateGradient(Strategy):
  def __call__(self, messenger):
    print self
    linedata = messenger
    # [ Actual test/calculation here ]
    result = LineData([7.7, 8.8]) # Dummy data
    result.setSuccessful(1)
    return result

solutions = []
solutions = [
  ChainLink(solutions, LeastSquares()),
  ChainLink(solutions, NewtonsMethod()),
  ChainLink(solutions, Bisection()),
  ChainLink(solutions, ConjugateGradient())
]

line = LineData([ 
  1.0, 2.0, 1.0, 2.0, -1.0, 
  3.0, 4.0, 5.0, 4.0 
])

print solutions[0](line)
#:~

CoffeeShop.py

2001-12-26T16:00:00Z

#: cX:decorator:nodecorators:CoffeeShop.py
# Coffee example with no decorators

class Espresso: pass
class DoubleEspresso: pass
class EspressoConPanna: pass

class Cappuccino:
  def __init__(self):
    self.cost = 1
    self.description = "Cappucino"
  def getCost(self):
    return self.cost
  def getDescription(self):
    return self.description

class CappuccinoDecaf: pass
class CappuccinoDecafWhipped: pass
class CappuccinoDry: pass
class CappuccinoDryWhipped: pass
class CappuccinoExtraEspresso: pass
class CappuccinoExtraEspressoWhipped: pass
class CappuccinoWhipped: pass

class CafeMocha: pass
class CafeMochaDecaf: pass
class CafeMochaDecafWhipped:
  def __init__(self):
    self.cost = 1.25
    self.description = \
      "Cafe Mocha decaf whipped cream"
  def getCost(self):
    return self.cost
  def getDescription(self):
    return self.description

class CafeMochaExtraEspresso: pass
class CafeMochaExtraEspressoWhipped: pass
class CafeMochaWet: pass
class CafeMochaWetWhipped: pass
class CafeMochaWhipped: pass

class CafeLatte: pass
class CafeLatteDecaf: pass
class CafeLatteDecafWhipped: pass
class CafeLatteExtraEspresso: pass
class CafeLatteExtraEspressoWhipped: pass
class CafeLatteWet: pass
class CafeLatteWetWhipped: pass
class CafeLatteWhipped: pass

cappuccino = Cappuccino()
print (cappuccino.getDescription() + ": $" + 
  `cappuccino.getCost()`)

cafeMocha = CafeMochaDecafWhipped()
print (cafeMocha.getDescription()
  + ": $" + `cafeMocha.getCost()`)
#:~

CommandPattern.py

2001-12-26T16:00:00Z

FlowerVisitors.py

2001-12-26T16:00:00Z

#: c11:FlowerVisitors.py
# Demonstration of "visitor" pattern.
from __future__ import generators
import random

# The Flower hierarchy cannot be changed:
class Flower(object):  
  def accept(self, visitor):
    visitor.visit(self)
  def pollinate(self, pollinator):
    print self, "pollinated by", pollinator
  def eat(self, eater):
    print self, "eaten by", eater
  def __str__(self): 
    return self.__class__.__name__

class Gladiolus(Flower): pass
class Runuculus(Flower): pass
class Chrysanthemum(Flower): pass 

class Visitor:
  def __str__(self): 
    return self.__class__.__name__

class Bug(Visitor): pass
class Pollinator(Bug): pass
class Predator(Bug): pass

# Add the ability to do "Bee" activities:
class Bee(Pollinator):
  def visit(self, flower):
      flower.pollinate(self)

# Add the ability to do "Fly" activities:
class Fly(Pollinator):
  def visit(self, flower):
      flower.pollinate(self)

# Add the ability to do "Worm" activities:
class Worm(Predator):
  def visit(self, flower):
      flower.eat(self)

def flowerGen(n):
  flwrs = Flower.__subclasses__()
  for i in range(n):
    yield random.choice(flwrs)()

# It's almost as if I had a method to Perform
# various "Bug" operations on all Flowers:
bee = Bee()
fly = Fly()
worm = Worm()
for flower in flowerGen(10):
  flower.accept(bee)
  flower.accept(fly)
  flower.accept(worm)
#:~

Games.py

2001-12-26T16:00:00Z

#: c05:Games.py
# An example of the Abstract Factory pattern.

class Obstacle:
  def action(self): pass

class Player:
  def interactWith(self, obstacle): pass

class Kitty(Player):
  def interactWith(self, obstacle):
    print "Kitty has encountered a",
    obstacle.action()

class KungFuGuy(Player):
  def interactWith(self, obstacle):
    print "KungFuGuy now battles a",
    obstacle.action()

class Puzzle(Obstacle):
  def action(self): 
    print "Puzzle" 

class NastyWeapon(Obstacle):
  def action(self): 
    print "NastyWeapon" 

# The Abstract Factory:
class GameElementFactory:
  def makePlayer(self): pass
  def makeObstacle(self): pass

# Concrete factories:
class KittiesAndPuzzles(GameElementFactory):
  def makePlayer(self): return Kitty()
  def makeObstacle(self): return Puzzle()

class KillAndDismember(GameElementFactory):
  def makePlayer(self): return KungFuGuy()
  def makeObstacle(self): return NastyWeapon()

class GameEnvironment:
  def __init__(self, factory):
    self.factory = factory
    self.p = factory.makePlayer() 
    self.ob = factory.makeObstacle()
  def play(self): 
    self.p.interactWith(self.ob) 

g1 = GameEnvironment(KittiesAndPuzzles())
g2 = GameEnvironment(KillAndDismember())
g1.play() 
g2.play() 
#:~

Games2.py

2001-12-26T16:00:00Z

MouseAction.py

2001-12-26T16:00:00Z

MouseMoves.txt

2001-12-26T16:00:00Z

mouse appears
mouse runs away
mouse appears
mouse enters trap
mouse escapes
mouse appears
mouse enters trap
mouse trapped
mouse removed
mouse appears
mouse runs away
mouse appears
mouse enters trap
mouse trapped
mouse removed

MouseTrap2Test.py

2001-12-26T16:00:00Z

#: c04:mousetrap2:MouseTrap2Test.py
# A better mousetrap using tables
import string, sys
sys.path += ['../statemachine', '../mouse']
from State import State
from StateMachine import StateMachine
from MouseAction import MouseAction

class StateT(State):
  def __init__(self):
    self.transitions = None
  def next(self, input):
    if self.transitions.has_key(input):
      return self.transitions[input]
    else:
      raise "Input not supported for current state"

class Waiting(StateT):
  def run(self): 
    print "Waiting: Broadcasting cheese smell"
  def next(self, input):
    # Lazy initialization:
    if not self.transitions:
      self.transitions = { 
        MouseAction.appears : MouseTrap.luring 
      }
    return StateT.next(self, input)

class Luring(StateT):
  def run(self):
    print "Luring: Presenting Cheese, door open"
  def next(self, input):
    # Lazy initialization:
    if not self.transitions:
      self.transitions = {
        MouseAction.enters : MouseTrap.trapping,
        MouseAction.runsAway : MouseTrap.waiting
      }
    return StateT.next(self, input)

class Trapping(StateT):
  def run(self):
    print "Trapping: Closing door"
  def next(self, input):
    # Lazy initialization:
    if not self.transitions:
      self.transitions = {
        MouseAction.escapes : MouseTrap.waiting,
        MouseAction.trapped : MouseTrap.holding
      }
    return StateT.next(self, input)

class Holding(StateT):
  def run(self):
    print "Holding: Mouse caught"
  def next(self, input):
    # Lazy initialization:
    if not self.transitions:
      self.transitions = {
        MouseAction.removed : MouseTrap.waiting
      }
    return StateT.next(self, input)

class MouseTrap(StateMachine):
  def __init__(self): 
    # Initial state
    StateMachine.__init__(self, MouseTrap.waiting)

# Static variable initialization:
MouseTrap.waiting = Waiting()
MouseTrap.luring = Luring()
MouseTrap.trapping = Trapping()
MouseTrap.holding = Holding()

moves = map(string.strip, 
  open("../mouse/MouseMoves.txt").readlines())
mouseMoves = map(MouseAction, moves)
MouseTrap().runAll(mouseMoves)
#:~

MouseTrapTest.py

2001-12-26T16:00:00Z

#: c04:mousetrap1:MouseTrapTest.py
# State Machine pattern using 'if' statements
# to determine the next state.
import string, sys
sys.path += ['../statemachine', '../mouse']
from State import State
from StateMachine import StateMachine
from MouseAction import MouseAction
# A different subclass for each state:

class Waiting(State):
  def run(self): 
    print "Waiting: Broadcasting cheese smell"

  def next(self, input):
    if input == MouseAction.appears:
      return MouseTrap.luring
    return MouseTrap.waiting

class Luring(State):
  def run(self):
    print "Luring: Presenting Cheese, door open"

  def next(self, input):
    if input == MouseAction.runsAway:
      return MouseTrap.waiting
    if input == MouseAction.enters:
      return MouseTrap.trapping
    return MouseTrap.luring

class Trapping(State):
  def run(self):
    print "Trapping: Closing door"

  def next(self, input):
    if input == MouseAction.escapes:
      return MouseTrap.waiting
    if input == MouseAction.trapped:
      return MouseTrap.holding
    return MouseTrap.trapping

class Holding(State):
  def run(self):
    print "Holding: Mouse caught"

  def next(self, input):
    if input == MouseAction.removed:
      return MouseTrap.waiting
    return MouseTrap.holding

class MouseTrap(StateMachine):
  def __init__(self): 
    # Initial state
    StateMachine.__init__(self, MouseTrap.waiting)

# Static variable initialization:
MouseTrap.waiting = Waiting()
MouseTrap.luring = Luring()
MouseTrap.trapping = Trapping()
MouseTrap.holding = Holding()

moves = map(string.strip, 
  open("../mouse/MouseMoves.txt").readlines())
MouseTrap().runAll(map(MouseAction, moves))
#:~

ObservedFlower.py

2001-12-26T16:00:00Z

#: c10:ObservedFlower.py
# Demonstration of "observer" pattern.
import sys
sys.path += ['../util']
from Observer import Observer, Observable

class Flower:
  def __init__(self): 
    self.isOpen = 0
    self.openNotifier = Flower.OpenNotifier(self)
    self.closeNotifier= Flower.CloseNotifier(self)
  def open(self): # Opens its petals
    self.isOpen = 1
    self.openNotifier.notifyObservers()
    self.closeNotifier.open()
  def close(self): # Closes its petals
    self.isOpen = 0
    self.closeNotifier.notifyObservers()
    self.openNotifier.close()
  def closing(self): return self.closeNotifier 

  class OpenNotifier(Observable):
    def __init__(self, outer):
      Observable.__init__(self)
      self.outer = outer
      self.alreadyOpen = 0
    def notifyObservers(self):
      if self.outer.isOpen and \
      not self.alreadyOpen:
        self.setChanged()
        Observable.notifyObservers(self)
        self.alreadyOpen = 1
    def close(self): 
      self.alreadyOpen = 0 

  class CloseNotifier(Observable):
    def __init__(self, outer):
      Observable.__init__(self)
      self.outer = outer
      self.alreadyClosed = 0
    def notifyObservers(self):
      if not self.outer.isOpen and \
      not self.alreadyClosed:
        self.setChanged()
        Observable.notifyObservers(self)
        self.alreadyClosed = 1
    def open(self): 
      alreadyClosed = 0 

class Bee:
  def __init__(self, name):
    self.name = name
    self.openObserver = Bee.OpenObserver(self)
    self.closeObserver = Bee.CloseObserver(self)
  # An inner class for observing openings:
  class OpenObserver(Observer):
    def __init__(self, outer):
      self.outer = outer
    def update(self, observable, arg):
      print "Bee " + self.outer.name + \
        "'s breakfast time!"
  # Another inner class for closings:
  class CloseObserver(Observer):
    def __init__(self, outer):
      self.outer = outer
    def update(self, observable, arg):
      print "Bee " + self.outer.name + \
        "'s bed time!"

class Hummingbird:
  def __init__(self, name): 
    self.name = name
    self.openObserver = \
      Hummingbird.OpenObserver(self)
    self.closeObserver = \
      Hummingbird.CloseObserver(self)
  class OpenObserver(Observer):
    def __init__(self, outer):
      self.outer = outer
    def update(self, observable, arg):
      print "Hummingbird " + self.outer.name + \
        "'s breakfast time!"
  class CloseObserver(Observer):
    def __init__(self, outer):
      self.outer = outer
    def update(self, observable, arg):
      print "Hummingbird " + self.outer.name + \
        "'s bed time!"

f = Flower()
ba = Bee("Eric")
bb = Bee("Eric 0.5")
ha = Hummingbird("A")
hb = Hummingbird("B")
f.openNotifier.addObserver(ha.openObserver)
f.openNotifier.addObserver(hb.openObserver)
f.openNotifier.addObserver(ba.openObserver)
f.openNotifier.addObserver(bb.openObserver)
f.closeNotifier.addObserver(ha.closeObserver)
f.closeNotifier.addObserver(hb.closeObserver)
f.closeNotifier.addObserver(ba.closeObserver)
f.closeNotifier.addObserver(bb.closeObserver)
# Hummingbird 2 decides to sleep in:
f.openNotifier.deleteObserver(hb.openObserver)
# A change that interests observers:
f.open()
f.open() # It's already open, no change.
# Bee 1 doesn't want to go to bed:
f.closeNotifier.deleteObserver(ba.closeObserver)
f.close()
f.close() # It's already closed; no change
f.openNotifier.deleteObservers()
f.open()
f.close()
#:~

Observer.py

2001-12-26T16:00:00Z

#: util:Observer.py
# Class support for "observer" pattern.
from Synchronization import *

class Observer:
  def update(observable, arg):
    '''Called when the observed object is 
    modified. You call an Observable object's 
    notifyObservers method to notify all the 
    object's observers of the change.'''
    pass

class Observable(Synchronization):
  def __init__(self):
    self.obs = []
    self.changed = 0
    Synchronization.__init__(self)

  def addObserver(self, observer):
    if observer not in self.obs:
      self.obs.append(observer)

  def deleteObserver(self, observer):
    self.obs.remove(observer)

  def notifyObservers(self, arg = None):
    '''If 'changed' indicates that this object 
    has changed, notify all its observers, then 
    call clearChanged(). Each observer has its 
    update() called with two arguments: this 
    observable object and the generic 'arg'.'''

    self.mutex.acquire()
    try:
      if not self.changed: return
      # Make a local copy in case of synchronous
      # additions of observers:
      localArray = self.obs[:]
      self.clearChanged()
    finally:
      self.mutex.release()
    # Updating is not required to be synchronized:
    for observer in localArray:
      observer.update(self, arg)

  def deleteObservers(self): self.obs = []
  def setChanged(self): self.changed = 1
  def clearChanged(self): self.changed = 0
  def hasChanged(self): return self.changed
  def countObservers(self): return len(self.obs)

synchronize(Observable, 
  "addObserver deleteObserver deleteObservers " +
  "setChanged clearChanged hasChanged " +
  "countObservers")
#:~

PaperScissorsRock.py

2001-12-26T16:00:00Z

#: 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)
#:~

PaperScissorsRock2.py

2001-12-26T16:00:00Z

#: c11:PaperScissorsRock2.py
# Multiple dispatching using a table
from __future__ import generators
import random

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 compete(self, item):
    # Use a tuple for table lookup:
    return outcome[self.__class__, item.__class__]
  def __str__(self): 
    return self.__class__.__name__ 

class Paper(Item): pass
class Scissors(Item): pass
class Rock(Item): pass

outcome = {
  (Paper, Rock): Outcome.WIN,
  (Paper, Scissors): Outcome.LOSE,
  (Paper, Paper): Outcome.DRAW,
  (Scissors, Paper): Outcome.WIN,
  (Scissors, Rock): Outcome.LOSE,
  (Scissors, Scissors): Outcome.DRAW,
  (Rock, Scissors): Outcome.WIN,
  (Rock, Paper): Outcome.LOSE,
  (Rock, Rock): 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)
#:~

ShapeFactory1.py

2001-12-26T16:00:00Z

ShapeFactory2.py

2001-12-26T16:00:00Z

#: c05:shapefact2:ShapeFactory2.py
# Polymorphic factory methods.
from __future__ import generators
import random

class ShapeFactory:
  factories = {}
  def addFactory(id, shapeFactory):
    ShapeFactory.factories.put[id] = shapeFactory
  addFactory = staticmethod(addFactory)
  # A Template Method:
  def createShape(id):
    if not ShapeFactory.factories.has_key(id):
      ShapeFactory.factories[id] = \
        eval(id + '.Factory()')
    return ShapeFactory.factories[id].create()
  createShape = staticmethod(createShape)

class Shape(object): pass

class Circle(Shape):
  def draw(self): print "Circle.draw" 
  def erase(self): print "Circle.erase"
  class Factory:
    def create(self): return Circle() 

class Square(Shape):
  def draw(self): 
    print "Square.draw" 
  def erase(self): 
    print "Square.erase" 
  class Factory:
    def create(self): return Square() 

def shapeNameGen(n):
  types = Shape.__subclasses__()
  for i in range(n):
    yield random.choice(types).__name__

shapes = [ ShapeFactory.createShape(i) 
           for i in shapeNameGen(7)]

for shape in shapes:
  shape.draw()
  shape.erase()
#:~

State.py

2001-12-26T16:00:00Z

StateDemo.py

2001-12-26T16:00:00Z

StateMachine.py

2001-12-26T16:00:00Z

StrategyPattern.py

2001-12-26T16:00:00Z

#: c06:StrategyPattern.py

# The strategy interface:
class FindMinima:
  # Line is a sequence of points:
  def algorithm(self, line) : pass

# The various strategies:
class LeastSquares(FindMinima):
  def algorithm(self, line):
    return [ 1.1, 2.2 ] # Dummy

class NewtonsMethod(FindMinima):
  def algorithm(self, line):
    return [ 3.3, 4.4 ]  # Dummy

class Bisection(FindMinima):
  def algorithm(self, line):
    return [ 5.5, 6.6 ] # Dummy

class ConjugateGradient(FindMinima):
  def algorithm(self, line):
    return [ 3.3, 4.4 ] # Dummy

# The "Context" controls the strategy:
class MinimaSolver:
  def __init__(self, strategy):
    self.strategy = strategy

  def minima(self, line):
    return self.strategy.algorithm(line)

  def changeAlgorithm(self, newAlgorithm):
    self.strategy = newAlgorithm

solver = MinimaSolver(LeastSquares())
line = [
    1.0, 2.0, 1.0, 2.0, -1.0, 3.0, 4.0, 5.0, 4.0 
  ]
print solver.minima(line)
solver.changeAlgorithm(Bisection())
print solver.minima(line)
#:~

Synchronization.py

2001-12-26T16:00:00Z

#: util:Synchronization.py
'''Simple emulation of Java's 'synchronized'
keyword, from Peter Norvig.'''
import threading

def synchronized(method):
  def f(*args):
    self = args[0]
    self.mutex.acquire();  
    # print method.__name__, 'acquired'
    try:
      return apply(method, args)
    finally:
      self.mutex.release();  
      # print method.__name__, 'released'
  return f

def synchronize(klass, names=None):
  """Synchronize methods in the given class.  
  Only synchronize the methods whose names are 
  given, or all methods if names=None."""
  if type(names)==type(''): names = names.split()
  for (name, val) in klass.__dict__.items():
    if callable(val) and name != '__init__' and \
      (names == None or name in names):
        # print "synchronizing", name
        klass.__dict__[name] = synchronized(val)

# You can create your own self.mutex, or inherit
# from this class:
class Synchronization:
  def __init__(self):
    self.mutex = threading.RLock()
#:~

TestSynchronization.py

2001-12-26T16:00:00Z

#: util:TestSynchronization.py
from Synchronization import * 

# To use for a method:
class C(Synchronization):
  def __init__(self):
    Synchronization.__init__(self)
    self.data = 1
  def m(self):
    self.data += 1
    return self.data
  m = synchronized(m)
  def f(self): return 47
  def g(self): return 'spam'

# So m is synchronized, f and g are not.
c = C()

# On the class level:
class D(C):
  def __init__(self):
    C.__init__(self)
  # You must override an un-synchronized method
  # in order to synchronize it (just like Java):
  def f(self): C.f(self)

# Synchronize every (defined) method in the class:
synchronize(D)
d = D()
d.f() # Synchronized
d.g() # Not synchronized
d.m() # Synchronized (in the base class)

class E(C):
  def __init__(self):
    C.__init__(self)
  def m(self): C.m(self)
  def g(self): C.g(self)
  def f(self): C.f(self)
# Only synchronizes m and g. Note that m ends up
# being doubly-wrapped in synchronization, which
# doesn't hurt anything but is inefficient:
synchronize(E, 'm g')
e = E()
e.f()
e.g()
e.m()
#:~