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.
Examples and references from: https://github.com/domnikl/DesignPatternsPHP
Design Patterns:
| Pattern | Description | |
|---|---|---|
| Static factory | Class with static method for creating object | 📄 📊 |
| Simple factory | Single class for creating objects | 📄 📊 |
| Factory method | "Define an interface for creating an object, but let the classes that implement the interface decide which class to instantiate. The Factory method lets a class defer instantiation to subclasses." | 📄 📊 📖 |
| Abstract factory | "Provide an interface for creating families of related or dependent objects without specifying their concrete classes." | 📄 📊 📖 |
All other Patterns:
| Pattern | Description |
|---|---|
| 3-tier | data<->business logic<->presentation separation (strict relationships) |
| 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 |
| 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 |
Abstract Factory allows to create several different type of instances in one sub-class, and to particularize the creations behavior in its different sub-classes; normally, Factory method declares the creation of only one type of object that can be particularized according to the sub-classing mechanism. http://stackoverflow.com/questions/4209791/design-patterns-abstract-factory-vs-factory-method