strategy.py

class StrategyExample:

    def __init__(self, func=None):
        if func:
            self.execute = func

    def execute(self):
        print "Original execution"


def executeReplacement1(self):
        print "Strategy 1"


def executeReplacement2(self):
    print "Strategy 2"

if __name__ == "__main__":

    strat0 = StrategyExample()
    strat1 = StrategyExample(executeReplacement1)
    strat2 = StrategyExample(executeReplacement2)

    strat0.execute()
    strat1.execute()
    strat2.execute()

# -------------------- With classes --------------------


class AUsefulThing(object):
    def __init__(self, aStrategicAlternative):
        self.howToDoX = aStrategicAlternative

    def doX(self, someArg):
        self. howToDoX.theAPImethod(someArg, self)


class StrategicAlternative(object):
    pass


class AlternativeOne(StrategicAlternative):
    def theAPIMethod(self, someArg, theUsefulThing):
        pass  # an implementation


class AlternativeTwo(StrategicAlternative):
    def theAPImethod(self, someArg, theUsefulThing):
        pass  # another implementation


t = AUsefulThing(AlternativeOne())
t.doX('arg')