Agent Skills: Python Logging

Python Logging

Overview

Choose the logging system based on project needs. Core principle: stdlib logging for libraries and ecosystem integration, loguru for fast, simple app/CLI logging.

Quick Reference

| Need | Use | | --- | --- | | Library or long-lived service | stdlib logging | | Simple app or CLI | loguru | | Integrations (Sentry/OTel) | stdlib logging |

Decision Rules

Use stdlib logging when:

• Building a reusable library
• You need handler hierarchies or integration with ops tooling

Use loguru when:

• You want minimal setup and readable output
• You are building a small app or CLI

Example

Stdlib logger setup:

import logging

logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)
logger.info("App started")

Common Mistakes

• Forcing loguru in a reusable library.
• Mixing two logging systems without a clear boundary.

Red Flags

• Logging recommendations with no rationale for library vs app use.

References

• references/logging.md - stdlib logging patterns
• references/loguru.md - loguru patterns