python-patterns

A collection of design patterns and idioms in Python.

When an implementation is added or modified, be sure to update this file and rerun append_output.sh (eg. ./append_output.sh borg.py) to keep the output comments at the bottom up to date.

Current Patterns:

Creational Patterns:

Pattern	Description
abstract_factory	use a generic function with specific factories
borg	a singleton with shared-state among instances
builder	instead of using multiple constructors, builder object receives parameters and returns constructed objects
factory_method	delegate a specialized function/method to create instances
lazy_evaluation	lazily-evaluated property pattern in Python
pool	preinstantiate and maintain a group of instances of the same type
prototype	use a factory and clones of a prototype for new instances (if instantiation is expensive)

Structural Patterns:

Pattern	Description
3-tier	data<->business logic<->presentation separation (strict relationships)
adapter	adapt one interface to another using a white-list
bridge	a client-provider middleman to soften interface changes
composite	encapsulate and provide access to a number of different objects
decorator	wrap functionality with other functionality in order to affect outputs
facade	use one class as an API to a number of others
flyweight	transparently reuse existing instances of objects with similar/identical state
front_controller	single handler requests coming to the application
mvc	model<->view<->controller (non-strict relationships)
proxy	an object funnels operations to something else

Behavioral Patterns:

Pattern	Description
chain	apply a chain of successive handlers to try and process the data
catalog	general methods will call different specialized methods based on construction parameter
chaining_method	continue callback next object method
command	bundle a command and arguments to call later
mediator	an object that knows how to connect other objects and act as a proxy
memento	generate an opaque token that can be used to go back to a previous state
observer	provide a callback for notification of events/changes to data
publish_subscribe	a source syndicates events/data to 0+ registered listeners
registry	keep track of all subclasses of a given class
specification	business rules can be recombined by chaining the business rules together using boolean logic
state	logic is organized into a discrete number of potential states and the next state that can be transitioned to
strategy	selectable operations over the same data
template	an object imposes a structure but takes pluggable components
visitor	invoke a callback for all items of a collection

Others:

Pattern	Description
blackboard	(architectural model, assemble different sub-system knowledge to build a solution, AI approach - non gang of four pattern)
graph_search	(graphing algorithms, not design patterns)

at3560k/python-patterns

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