python-patterns

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:

Pattern	Description
3-tier	data<->business logic<->presentation separation (strict relationships)
abstract_factory	use a generic function with specific factories
adapter	adapt one interface to another using a whitelist
borg	a singleton with shared-state among instances
bridge	a client-provider middleman to soften interface changes
builder	call many little discrete methods rather than having a huge number of constructor parameters
catalog	general methods will call different specialized methods based on construction parameter
chain	apply a chain of successive handlers to try and process the data
command	bundle a command and arguments to call later
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
factory_method	delegate a specialized function/method to create instances
flyweight	transparently reuse existing instances of objects with similar/identical state
graph_search	(graphing algorithms, not design patterns)
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
mvc	model<->view<->controller (non-strict relationships)
observer	provide a callback for notification of events/changes to data
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)
proxy	an object funnels operations to something else
publish_subscribe	a source syndicates events/data to 0+ registered listeners
state	logic is org'd 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
chaining_method	continue callback next object method