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‎.travis.yml‎

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# vim ft=yaml
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# travis-ci.org definition for python-patterns build
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language: python
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sudo: false
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python:
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- "2.7"
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- "3.3"
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- "3.4"
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- "3.5"
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# Disabled for now since cause more pain than gain
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# - "pypy"
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# - "pypy3"
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cache:
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- pip
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install:
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- travis_retry pip install -q coveralls codecov
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- pip install flake8 # eventually worth
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script:
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# Run tests
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- PYTHONPATH=. nosetests -s -v --with-doctest --with-cov --cover-package . --logging-level=INFO -v .
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# Actually run all the scripts, contributing to coverage
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- ./run_all.sh
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# for now failure in flaking is ignored
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- flake8 *py || echo "PEP8 the code"
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after_success:
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- coveralls
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- codecov

‎3-tier.py‎

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44

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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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""" Business logic holding data store instances """
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def __init__(self):
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self.data = Data()
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data = Data()
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def product_list(self):
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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()
@@ -59,14 +65,19 @@ def main():
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### OUTPUT ###
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# PRODUCT LIST:
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# (Fetching from Data Store)
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# cheese
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# eggs
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# milk
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# cheese
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#
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#
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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
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===============
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4-
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` to keep the output comments at the bottom up to date.
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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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Current Patterns:
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* 3-tier
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* abstract_factory
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* adapter
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* borg
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* bridge
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* builder
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* catalog
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* chain
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* command
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* composite
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* decorator
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* facade
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* factory_method
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* flyweight
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* graph_search
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* iterator
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* mediator
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* memento
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* mvc
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* null
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* observer
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* pool
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* prototype
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* proxy
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* publish_subscribe
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* state
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* strategy
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* template
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* visitor
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__Creational Patterns__:
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| Pattern | Description |
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|:-------:| ----------- |
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| [abstract_factory](abstract_factory.py) | use a generic function with specific factories |
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| [borg](borg.py) | a singleton with shared-state among instances |
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| [builder](builder.py) | instead of using multiple constructors, builder object receives parameters and returns constructed objects |
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| [factory_method](factory_method.py) | delegate a specialized function/method to create instances |
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| [lazy_evaluation](lazy_evaluation.py) | lazily-evaluated property pattern in Python |
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| [pool](pool.py) | preinstantiate and maintain a group of instances of the same type |
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| [prototype](prototype.py) | use a factory and clones of a prototype for new instances (if instantiation is expensive) |
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__Structural Patterns__:
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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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| [adapter](adapter.py) | adapt one interface to another using a white-list |
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| [bridge](bridge.py) | a client-provider middleman to soften interface changes |
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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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| [flyweight](flyweight.py) | transparently reuse existing instances of objects with similar/identical state |
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| [front_controller](front_controller.py) | single handler requests coming to the application |
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| [mvc](mvc.py) | model<->view<->controller (non-strict relationships) |
37+
| [proxy](proxy.py) | an object funnels operations to something else |
38+
39+
__Behavioral Patterns__:
40+
41+
| Pattern | Description |
42+
|:-------:| ----------- |
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| [chain](chain.py) | apply a chain of successive handlers to try and process the data |
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| [catalog](catalog.py) | general methods will call different specialized methods based on construction parameter |
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| [chaining_method](chaining_method.py) | continue callback next object method |
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| [command](command.py) | bundle a command and arguments to call later |
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| [mediator](mediator.py) | an object that knows how to connect other objects and act as a proxy |
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| [memento](memento.py) | generate an opaque token that can be used to go back to a previous state |
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| [observer](observer.py) | provide a callback for notification of events/changes to data |
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| [publish_subscribe](publish_subscribe.py) | a source syndicates events/data to 0+ registered listeners |
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| [registry](registry.py) | keep track of all subclasses of a given class |
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| [specification](specification.py) | business rules can be recombined by chaining the business rules together using boolean logic |
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| [state](state.py) | logic is organized into a discrete number of potential states and the next state that can be transitioned to |
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| [strategy](strategy.py) | selectable operations over the same data |
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| [template](template.py) | an object imposes a structure but takes pluggable components |
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| [visitor](visitor.py) | invoke a callback for all items of a collection |
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__Others__:
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| Pattern | Description |
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|:-------:| ----------- |
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| [graph_search](graph_search.py) | (graphing algorithms, not design patterns) |

‎__init__.py‎

Whitespace-only changes.

‎abstract_factory.py‎

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@@ -13,19 +13,17 @@ 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
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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()
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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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# Show pets with various factories
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if __name__ == "__main__":
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shop = PetShop()
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for i in range(3):
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shop.pet_factory = get_factory()
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shop = PetShop(get_factory())
8279
shop.show_pet()
8380
print("=" * 20)
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### OUTPUT ###
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# This is a lovely Dog
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# We have a lovely Dog
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# It says woof
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# It eats dog food
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# We also have dog food
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# ====================
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# This is a lovely Cat
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# It says meow
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# It eats cat food
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# ====================
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# This is a lovely Dog
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# We have a lovely Dog
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# It says woof
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# It eats dog food
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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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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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class Cat(object):
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def __init__(self):
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self.name = "Cat"
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class Human(object):
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def __init__(self):
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self.name = "Human"
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3631
class Car(object):
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def __init__(self):
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self.name = "Car"
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class Adapter(object):
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"""
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Adapts an object by replacing methods.
4942
Usage:
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>>> objects = []
5447
>>> dog = Dog()
55-
>>> objects.append(Adapter(dog, dict(make_noise=dog.bark)))
48+
>>> print(dog.__dict__)
49+
{'name': 'Dog'}
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>>> objects.append(Adapter(dog, make_noise=dog.bark))
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>>> print(objects[0].original_dict())
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{'name': 'Dog'}
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>>> cat = Cat()
57-
>>> objects.append(Adapter(cat, dict(make_noise=cat.meow)))
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>>> objects.append(Adapter(cat, make_noise=cat.meow))
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>>> human = Human()
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>>> objects.append(Adapter(human, dict(make_noise=human.speak)))
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>>> objects.append(Adapter(human, make_noise=human.speak))
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>>> car = Car()
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>>> car_noise = lambda: car.make_noise(3)
62-
>>> objects.append(Adapter(car, dict(make_noise=car_noise)))
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>>> objects.append(Adapter(car, make_noise=car_noise))
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>>> for obj in objects:
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... print('A {} goes {}'.format(obj.name, obj.make_noise()))
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6966
A Car goes vroom!!!
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"""
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def __init__(self, obj, adapted_methods):
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def __init__(self, obj, **adapted_methods):
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"""We set the adapted methods in the object's dict"""
7471
self.obj = obj
7572
self.__dict__.update(adapted_methods)
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7774
def __getattr__(self, attr):
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"""All non-adapted calls are passed to the object"""
7976
return getattr(self.obj, attr)
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78+
def original_dict(self):
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"""Print original object dict"""
80+
return self.obj.__dict__
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8282
def main():
8383
objects = []
8484
dog = Dog()
85-
objects.append(Adapter(dog, dict(make_noise=dog.bark)))
85+
print(dog.__dict__)
86+
objects.append(Adapter(dog, make_noise=dog.bark))
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print(objects[0].__dict__)
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print(objects[0].original_dict())
8689
cat = Cat()
87-
objects.append(Adapter(cat, dict(make_noise=cat.meow)))
90+
objects.append(Adapter(cat, make_noise=cat.meow))
8891
human = Human()
89-
objects.append(Adapter(human, dict(make_noise=human.speak)))
92+
objects.append(Adapter(human, make_noise=human.speak))
9093
car = Car()
91-
objects.append(Adapter(car, dict(make_noise=lambda: car.make_noise(3))))
94+
objects.append(Adapter(car, make_noise=lambda: car.make_noise(3)))
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9396
for obj in objects:
9497
print("A {0} goes {1}".format(obj.name, obj.make_noise()))
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98101
main()
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100103
### OUTPUT ###
104+
# {'name': 'Dog'}
105+
# {'make_noise': <bound method Dog.bark of <__main__.Dog object at 0x7f631ba3fb00>>, 'obj': <__main__.Dog object at 0x7f631ba3fb00>}
106+
# {'name': 'Dog'}
101107
# A Dog goes woof!
102108
# A Cat goes meow!
103109
# A Human goes 'hello'

‎append_output.sh‎

100644100755
File mode changed.

‎borg.py‎

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88
def __init__(self):
99
self.__dict__ = self.__shared_state
10+
self.state = 'Init'
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1112
def __str__(self):
1213
return self.state
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4445
# rm2: Running
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# rm1: Zombie
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# rm2: Zombie
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# rm1 id: 139825262601040
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# rm2 id: 139825262601104
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# rm1: Zombie
50-
# rm2: Zombie
51-
# rm3: Zombie
48+
# rm1 id: 140732837899224
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# rm2 id: 140732837899296
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# rm1: Init
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# rm2: Init
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# rm3: Init

‎builder.py‎

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3131
def new_building(self):
3232
self.building = Building()
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34+
def build_floor(self):
35+
raise NotImplementedError
36+
37+
def build_size(self):
38+
raise NotImplementedError
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3540
# Concrete Builder
3641
class BuilderHouse(Builder):

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