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Lucene is mature, open-source, highly performing, scalable, light and, yet, very powerful. It also has a very strong community that supports it. Its core comes as a single file of Java library with no dependencies, and allows you to index documents and search them with its out-of-the-box full text search capabilities.

Each Python class definition has an implicit superclass: object.

When we define our own class, object is the superclass.

The superclass of all classes, object, has a default implementation of __init__() that amounts to pass. We aren't required to implement __init__(). If we don't implement it, then no instance variables will be created when the object is created.

Refactoring is better than adding if statements.

"Explicit is better than implicit."

In this example, we factored the __init__() method into the superclass so that a common initialization in the superclass, Card, applies to all the three subclasses NumberCard, AceCard, and FaceCard.

A small domain of static objects may be part of implementing a Strategy or State design pattern.
In some cases, we may have a pool of constant objects created in an initialization or configuration file, or we might create constant objects based on command-line parameters.

This can make the Strategy or State design patterns work efficiently by reusing objects from a small, static pool of constants.

We define a function that creates objects of the required classes.
We define a class that has methods for creating objects. This is the full factory design pattern, as described in books on design patterns. In languages such as Java, a factory class hierarchy is required because the language doesn't support standalone functions.