Behavioral Design Pattern
Behavioral Design Patterns in Python
Behavioral patterns are concerned with algorithms and the assignment of responsibilities between objects. They characterize complex control flow that’s difficult to follow at run-time.
1. Observer Pattern
The Observer pattern lets you define a subscription mechanism to notify multiple objects about any events that happen to the object they’re observing.
1.1 Example: Weather Station
1.2 Benefits of Observer
- Supports the principle of loose coupling between objects
- Allows sending data to many objects efficiently
- Dynamic relationships can be established between objects at runtime
2. Strategy Pattern
The Strategy pattern lets you define a family of algorithms, put each of them into a separate class, and make their objects interchangeable.
2.1 Example: Payment Processing
2.2 Benefits of Strategy
- Allows switching algorithms used inside an object at runtime
- Isolates the implementation details of an algorithm from the code that uses it
- Replaces inheritance with composition
3. Command Pattern
The Command pattern turns a request into a stand-alone object that contains all information about the request.
3.1 Example: Remote Control
3.2 Benefits of Command
- Decouples classes that invoke operations from classes that perform these operations
- Allows creating sequences of commands with a macro command
- Supports undo operations
4. State Pattern
The State pattern lets an object alter its behavior when its internal state changes. It appears as if the object changed its class.
4.1 Example: Vending Machine
4.2 Benefits of State
- Organizes code related to particular states into separate classes
- Makes state transitions explicit
- Simplifies the code by eliminating bulky state machine conditional statements
5. Chain of Responsibility Pattern
The Chain of Responsibility pattern lets you pass requests along a chain of handlers. Upon receiving a request, each handler decides either to process the request or to pass it to the next handler in the chain.
5.1 Example: Logger Levels
5.2 Benefits of Chain of Responsibility
- Reduces coupling between components
- Increases flexibility in assigning responsibilities to objects
- Allows adding or removing responsibilities dynamically
6. Template Method Pattern
The Template Method pattern defines the skeleton of an algorithm in the superclass but lets subclasses override specific steps of the algorithm without changing its structure.
6.1 Example: Beverage Preparation
6.2 Benefits of Template Method
- Lets subclasses implement varying behavior
- Avoids code duplication
- Allows fine-grained control over the steps of an algorithm
Conclusion
Behavioral design patterns are crucial for managing algorithms, relationships, and responsibilities between objects. They improve communication between objects, make complex control flows more manageable, and help distribute responsibilities efficiently. By applying these patterns, developers can create more flexible and maintainable code structures that are easier to understand and modify.