python-patterns/strategy.py at master · linuxster/python-patterns · GitHub

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# http://stackoverflow.com/questions/963965/how-is-this-strategy-pattern

# -written-in-python-the-sample-in-wikipedia

"""

In most of other languages Strategy pattern is implemented via creating some

base strategy interface/abstract class and subclassing it with a number of

concrete strategies (as we can see at

http://en.wikipedia.org/wiki/Strategy_pattern), however Python supports

higher-order functions and allows us to have only one class and inject

functions into it's instances, as shown in this example.

"""

import types

class StrategyExample:

def __init__(self, func=None):

self.name = 'Strategy Example 0'

if func is not None:

self.execute = types.MethodType(func, self)

def execute(self):

print(self.name)

def execute_replacement1(self):

print(self.name + ' from execute 1')

def execute_replacement2(self):

print(self.name + ' from execute 2')

if __name__ == '__main__':

strat0 = StrategyExample()

strat1 = StrategyExample(execute_replacement1)

strat1.name = 'Strategy Example 1'

strat2 = StrategyExample(execute_replacement2)

strat2.name = 'Strategy Example 2'

strat0.execute()

strat1.execute()

strat2.execute()

### OUTPUT ###

# Strategy Example 0

# Strategy Example 1 from execute 1

# Strategy Example 2 from execute 2

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