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python-result-pattern

Replace exceptions with a typed Result pattern for Python error handling.

1|2|Updated Dec 4, 2025
Search Tags:#testing#python#type-safety#error-handling#result#functional-pattern
One-click install
npx skills add https://github.com/co-labs-co/context-harness --skill python-result-pattern
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: python-result-pattern
Source: https://github.com/co-labs-co/context-harness/tree/main/.opencode/skill/python-result-pattern
Command: npx skills add https://github.com/co-labs-co/context-harness --skill python-result-pattern

SYSTEM DOCUMENTATION & REQUIREMENTS

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.

Frequently Asked Questions about python-result-pattern

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I handle errors in Python without raising exceptions for control flow?▼

Error handling in Python can be made explicit by replacing exceptions with a Result pattern, returning a typed Success or Failure object to make outcomes visible in function signatures and enforce consistent propagation.

What is the best way to standardize error propagation for Python service methods?▼

Standardizing error propagation is achieved by applying a Result pattern with a typed Outcome model, an ErrorCode enum, and helper factories to return structured failures for I/O, validation, or external calls instead of raising exceptions.

How do I implement type-safe error handling for Python I/O and validation operations?▼

Type-safe error handling is implemented by annotating functions with a Result[T] return type, returning Success(value) or Failure(error, code, details), and checking outcomes with isinstance to propagate structured errors explicitly.

Does replacing exceptions with a Result pattern improve Python testability?▼

Replacing exceptions with a Result pattern improves testability by enforcing explicit type checks for Success and Failure, eliminating hidden exception paths and making error propagation clear and predictable in service methods.

When should I use the Result pattern instead of standard exceptions in Python?▼

The Result pattern should be used for service methods that can fail, such as I/O, validation, or external calls, where making success and failure explicit in the function signature is preferred over exception-based control flow.

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