A collection of design patterns and idioms in Python.
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 | lets clients treat individual objects and compositions uniformly |
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 |
iterator | traverse a container and access the container's elements |
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 |
Design for Testability Patterns:
Pattern | Description |
---|---|
setter_injection | the client provides the depended-on object to the SUT via the setter injection (implementation variant of dependency injection) |
Fundamental Patterns:
Pattern | Description |
---|---|
delegation_pattern | an object handles a request by delegating to a second object (the delegate) |
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 - non gang of four pattern |
hsm | hierarchical state machine - non gang of four pattern |