abcls

abcls refers to abstract base classes in Python. They are a feature of the `abc` module that allows developers to define abstract classes, which are classes that cannot be instantiated on their own. Instead, they serve as blueprints for concrete subclasses. Abstract base classes are primarily used to define interfaces. They can specify methods that subclasses must implement, but they do not provide the implementation themselves.

To create an abstract base class in Python, one typically inherits from `abc.ABC` and uses the `@abc.abstractmethod` decorator to mark methods that must be implemented by concrete subclasses. If a subclass fails to implement all abstract methods, it cannot be instantiated, and Python will raise a `TypeError` at runtime. This mechanism helps enforce a consistent structure and behavior across different implementations of the same interface, promoting code reusability and maintainability.

Abstract base classes are not just for enforcing method implementation. They can also be used to define common functionality or default behaviors that subclasses can inherit and override if needed. This approach is particularly useful in scenarios where you want to define a set of expected behaviors for a particular type of object without dictating the exact implementation details. For example, you might create an abstract base class for different types of data readers, specifying methods like `read_data` and `close_file`, but allowing subclasses to implement the specific logic for reading from files, databases, or network streams.