pyrogenseither

pyrogenseither is a Python library that implements the Either monad for functional error handling. Drawing from Haskell and Scala patterns, it provides a clear distinction between successful results and errors without raising exceptions. The core types are Left and Right, representing failure and success, respectively. The library emphasizes composability, allowing complex workflows to be built from small, predictable transformations.

Core API and data types: Either is a generic type parameterized by the error type and the value type. Instances are created with Left(error) or Right(value). Common operations include map (to transform the value on the Right), bind/flat_map (to chain computations that may fail), and apply for applicative style composition. Convenience methods include is_left, is_right, unwrap_or, unwrap_or_else, and either which folds to a final result based on the side.

Interoperability and typing: pyrogenseither supports Python 3.7 and later, with type hints via typing.Generic, TypeVar, and Optional. It can integrate with existing exception-handling code by converting exceptions into Left values and vice versa through helper utilities. It also plays well with pattern matching features introduced in newer Python versions.

Design and usage: The library encourages explicit handling of errors through composition rather than silent exceptions. It can be used to model IO, parsing, and validation pipelines, providing clearer failure paths and easier testing. Compared with ad-hoc error flags or exceptions, Either promotes deterministic control flow in functional-style code.