Design Pattern

Hello and happy new year! 🥳🙌 I’ve made a video on how to implement the singleton pattern in Python using the LRU cache. Thank you!

Hello, In this short article I would like to talk about context managers. I personally consider that at the core they are just a form of decorators. If you don’t know what a decorator is check the Decorator Pattern Wikipedia article. Decorators can be used to implement cross-cutting concerns. We have componentA and we need logging and security, we could write the logic for logging and security handling in componentA but some people consider component a should be componentA not componentAthatAlsoKnowsAboutSecurityAndOtherStuff. Since it’s not the component’s responsibility to authorize requests or log calls to a external logging service, we can wrap the componentA into a decorator that does just that. ...

Hello, In this article we’re going to explore the Method Injection and Property Injection design patterns. To demonstrate the patterns I’m going to add a new interface named Encoder to the printer.py file and a concrete implementation for two encoders: Rot13Encoder and NullEncoder. 1 2 3 4 5 6 7 8 9 10 11 12 13 class Encoder(metaclass=abc.ABCMeta): def encode(self, message: Message) -> Message: raise NotImplementedError("encode must be implemented!") class Rot13Encoder(metaclass=abc.ABCMeta): def encode(self, message: Message) -> Message: return Message(codecs.encode(str(message), 'rot_13')) class NullEncoder(metaclass=abc.ABCMeta): def encode(self, message: Message) -> Message: return message The Encoder will be used by the printer in order to encode the messages before printing them. ...

The Constructor Injection design pattern is a pattern that helps you declare all the required dependencies of a class in it’s constructor. This is useful because it helps you decouple the code, you can specify an interface instead of a concrete type, remember, program to an interface. Also, in the constructor it is easier to guard against null objects. The calling code doesn’t have to worry about null exceptions every time it uses a dependency. ...

The composition root is a design pattern which helps you structure a software application by implementing a class that builds all the other classes. In this example we will examine this pattern in Python. Here’s the object graph of the classes that we’re going to implement: I have designed a sample application that we’re going to use. It contains three components: ConsoleInputListener, ConsolePrinter and RomanianTranslator and a value object class: Message. ...