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Merge pull request faif#1 from faif/master
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2 parents 11b4b6a + c10a94e commit 640cf76

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‎.gitignore‎

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__pycache__

‎3-tier.py‎

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class Data(object):
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""" Data Store Class """
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products = {
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'milk': {'price': 1.50, 'quantity': 10},
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'eggs': {'price': 0.20, 'quantity': 100},
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'cheese': {'price': 2.00, 'quantity': 10}
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}
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def __get__(self, obj, klas):
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print ("(Fetching from Data Store)")
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return {'products': self.products}
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class BusinessLogic(object):
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def __init__(self):
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self.data = Data()
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""" Business logic holding data store instances """
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data = Data()
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def product_list(self):
20-
return self.data.products.keys()
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return self.data['products'].keys()
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def product_information(self, product):
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return self.data.products.get(product, None)
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return self.data['products'].get(product, None)
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class Ui(object):
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""" UI interaction class """
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def __init__(self):
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self.business_logic = BusinessLogic()
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def get_product_list(self):
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print('PRODUCT LIST:')
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for product in self.business_logic.product_list():
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print(product)
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#print(product)
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yield product
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print('')
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def get_product_information(self, product):
@@ -56,3 +64,16 @@ def main():
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if __name__ == '__main__':
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main()
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### OUTPUT ###
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# (Fetching from Data Store)
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# PRODUCT INFORMATION:
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# Name: Cheese, Price: 2.00, Quantity: 10
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# (Fetching from Data Store)
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# PRODUCT INFORMATION:
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# Name: Eggs, Price: 0.20, Quantity: 100
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# (Fetching from Data Store)
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# PRODUCT INFORMATION:
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# Name: Milk, Price: 1.50, Quantity: 10
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# (Fetching from Data Store)
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# That product "arepas" does not exist in the records

‎README.md‎

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11
python-patterns
22
===============
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A collection of design patterns implemented (by other people) in python
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A collection of design patterns and idioms in Python.
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When an implementation is added or modified, be sure to update this file and
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rerun `append_output.sh` (eg. ./append_output.sh borg.py) to keep the output
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comments at the bottom up to date.
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610
Current Patterns:
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8-
* 3-tier
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* composite
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* mvc
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* decorator
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* null
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* facade
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* observer
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* abstract_factory
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* factory_method
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* pool
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* adapter
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* flyweight
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* prototype
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* borg
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* proxy
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* bridge
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* graph_search
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* state
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* builder
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* iterator
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* strategy
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* chain
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* mediator
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* template
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* command
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* memento
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* visitor
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| Pattern | Description |
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|:-------:| ----------- |
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| [3-tier](3-tier.py) | data<->business logic<->presentation separation (strict relationships) |
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| [abstract_factory](abstract_factory.py) | use a generic function with specific factories |
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| [adapter](adapter.py) | adapt one interface to another using a whitelist |
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| [borg](borg.py) | a singleton with shared-state among instances |
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| [bridge](bridge.py) | a client-provider middleman to soften interface changes |
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| [builder](builder.py) | call many little discrete methods rather than having a huge number of constructor parameters |
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| [catalog](catalog.py) | general methods will call different specialized methods based on construction parameter |
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| [chain](chain.py) | apply a chain of successive handlers to try and process the data |
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| [command](command.py) | bundle a command and arguments to call later |
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| [composite](composite.py) | encapsulate and provide access to a number of different objects |
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| [decorator](decorator.py) | wrap functionality with other functionality in order to affect outputs |
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| [facade](facade.py) | use one class as an API to a number of others |
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| [factory_method](factory_method.py) | delegate a specialized function/method to create instances |
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| [flyweight](flyweight.py) | transparently reuse existing instances of objects with similar/identical state |
28+
| [graph_search](graph_search.py) | (graphing algorithms, not design patterns) |
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| [mediator](mediator.py) | an object that knows how to connect other objects and act as a proxy |
30+
| [memento](memento.py) | generate an opaque token that can be used to go back to a previous state |
31+
| [mvc](mvc.py) | model<->view<->controller (non-strict relationships) |
32+
| [observer](observer.py) | provide a callback for notification of events/changes to data |
33+
| [pool](pool.py) | preinstantiate and maintain a group of instances of the same type |
34+
| [prototype](prototype.py) | use a factory and clones of a prototype for new instances (if instantiation is expensive) |
35+
| [proxy](proxy.py) | an object funnels operations to something else |
36+
| [publish_subscribe](publish_subscribe.py) | a source syndicates events/data to 0+ registered listeners |
37+
| [state](state.py) | logic is org'd into a discrete number of potential states and the next state that can be transitioned to |
38+
| [strategy](strategy.py) | selectable operations over the same data |
39+
| [template](template.py) | an object imposes a structure but takes pluggable components |
40+
| [visitor](visitor.py) | invoke a callback for all items of a collection |
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| [chaining_method](chaining_method.py) | continue callback next object method |

‎__pycache__/facade.cpython-33.pyc‎

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‎__pycache__/mediator.cpython-33.pyc‎

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‎abstract_factory.py‎

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#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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14
# http://ginstrom.com/scribbles/2007/10/08/design-patterns-python-style/
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"""Implementation of the abstract factory pattern"""
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import random
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class PetShop:
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"""A pet shop"""
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def __init__(self, animal_factory=None):
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"""pet_factory is our abstract factory.
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We can set it at will."""
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"""pet_factory is our abstract factory. We can set it at will."""
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self.pet_factory = animal_factory
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def show_pet(self):
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"""Creates and shows a pet using the
19-
abstract factory"""
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"""Creates and shows a pet using the abstract factory"""
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pet = self.pet_factory.get_pet()
22-
print("This is a lovely {}".format(pet))
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print("We have a lovely {}".format(pet))
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print("It says {}".format(pet.speak()))
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print("It eats {}".format(self.pet_factory.get_food()))
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print("We also have {}".format(self.pet_factory.get_food()))
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# Stuff that our factory makes
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class Dog:
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def speak(self):
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return "woof"
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class Cat:
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def speak(self):
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return "meow"
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@@ -45,6 +48,7 @@ def __str__(self):
4548
# Factory classes
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class DogFactory:
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def get_pet(self):
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return Dog()
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class CatFactory:
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5661
def get_pet(self):
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return Cat()
5863

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def get_food(self):
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return "cat food"
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62-
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# Create the proper family
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def get_factory():
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"""Let's be dynamic!"""
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# Show pets with various factories
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if __name__ == "__main__":
71-
shop = PetShop()
7275
for i in range(3):
73-
shop.pet_factory = get_factory()
76+
shop = PetShop(get_factory())
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shop.show_pet()
7578
print("=" * 20)
79+
80+
### OUTPUT ###
81+
# We have a lovely Dog
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# It says woof
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# We also have dog food
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# ====================
85+
# We have a lovely Dog
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# It says woof
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# We also have dog food
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# ====================
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# We have a lovely Cat
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# It says meow
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# We also have cat food
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# ====================

‎adapter.py‎

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# http://ginstrom.com/scribbles/2008/11/06/generic-adapter-class-in-python/
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#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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import os
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"""http://ginstrom.com/scribbles/2008/11/06/generic-adapter-class-in-python/"""
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6+
import os
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class Dog(object):
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def __init__(self):
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self.name = "Dog"
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def bark(self):
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return "woof!"
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13-
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class Cat(object):
1515
def __init__(self):
1616
self.name = "Cat"
17-
1817
def meow(self):
1918
return "meow!"
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21-
2220
class Human(object):
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def __init__(self):
2422
self.name = "Human"
25-
2623
def speak(self):
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return "'hello'"
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class Car(object):
3128
def __init__(self):
3229
self.name = "Car"
33-
3430
def make_noise(self, octane_level):
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return "vroom{0}".format("!" * octane_level)
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class Adapter(object):
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3936
"""
4037
Adapts an object by replacing methods.
4138
Usage:
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6057
A Human goes 'hello'
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A Car goes vroom!!!
6259
"""
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def __init__(self, obj, adapted_methods):
6462
"""We set the adapted methods in the object's dict"""
6563
self.obj = obj
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8886
if __name__ == "__main__":
89-
import doctest
90-
doctest.testmod()
87+
main()
88+
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### OUTPUT ###
90+
# A Dog goes woof!
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# A Cat goes meow!
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# A Human goes 'hello'
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# A Car goes vroom!!!

‎append_output.sh‎

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#!/bin/bash
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set -e
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src=$(sed -n -e '/### OUTPUT ###/,$!p' "$1")
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output=$(python "$1" | sed 's/^/# /')
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# These are done separately to avoid having to insert a newline, which causes
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# problems when the text itself has '\n' in strings
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echo "$src" > $1
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echo -e "\n### OUTPUT ###" >> $1
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echo "$output" >> $1

‎borg.py‎

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#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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class Borg:
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__shared_state = {}
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def __init__(self):
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self.__dict__ = self.__shared_state
10+
self.state = 'Init'
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712
def __str__(self):
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return self.state
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1823
rm1.state = 'Idle'
1924
rm2.state = 'Running'
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21-
print('rm1:', rm1)
22-
print('rm2:', rm2)
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print('rm1: {0}'.format(rm1))
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print('rm2: {0}'.format(rm2))
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2429
rm2.state = 'Zombie'
2530

26-
print('rm1:', rm1)
27-
print('rm2:', rm2)
31+
print('rm1: {0}'.format(rm1))
32+
print('rm2: {0}'.format(rm2))
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29-
print('rm1 id:', id(rm1))
30-
print('rm2 id:', id(rm2))
34+
print('rm1 id: {0}'.format(id(rm1)))
35+
print('rm2 id: {0}'.format(id(rm2)))
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3237
rm3 = YourBorg()
3338

34-
print('rm1:', rm1)
35-
print('rm2:', rm2)
36-
print('rm3:', rm3)
39+
print('rm1: {0}'.format(rm1))
40+
print('rm2: {0}'.format(rm2))
41+
print('rm3: {0}'.format(rm3))
42+
43+
### OUTPUT ###
44+
# rm1: Running
45+
# rm2: Running
46+
# rm1: Zombie
47+
# rm2: Zombie
48+
# rm1 id: 140732837899224
49+
# rm2 id: 140732837899296
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# rm1: Init
51+
# rm2: Init
52+
# rm3: Init

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