python-result-pattern

What problem does it solve?

The Result pattern provides explicit, type-safe error handling in Python, replacing exceptions for control flow and making errors visible in function signatures.

Core Features & Use Cases

• Define a discriminated union type Result[T] with Success[T] and Failure to represent outcomes.
• Standardize error handling with an ErrorCode enum and helper factories (success, failure) to propagate structured errors.
• Improve testability and readability by enforcing explicit error propagation and type checks (isinstance(result, Success/Failure)).
• Use Case: Apply the pattern to service methods that can fail (I/O, validation, external calls) to propagate failures to callers instead of raising exceptions.

Quick Start

Steps:

• Create a function that returns Result[T], annotate its return type as Result[YourType].
• Return Success(value) on success or Failure(error, code, details) on failure.
• In callers, check with isinstance(result, Failure) to propagate errors, or extract value when Success.