What is a PEP?

Python Enhancement Proposals (PEPs) are the foundational documents that guide Python’s evolution. They propose new language features, collect community input on issues, and document Python design decisions. They record the language’s history and future direction through carefully deliberated proposals.

Not all PEPs are accepted. Rejected PEPs often contain valuable discussion and insights about Python’s design philosophy.

Core Purpose and Process

PEPs serve multiple functions in Python’s ecosystem:

• Technical Specifications: They provide detailed descriptions for new language features or processes
• Community Discussion: PEPs facilitate structured debate about Python’s development
• Historical Record: They document the rationale behind language decisions
• Status Tracking: PEPs track the progress of proposals from draft through acceptance or rejection

Anatomy of a PEP

PEPs are structured as formal design documents containing:

• A concise abstract outlining the proposal
• Motivation and rationale for the changes
• Technical specifications and implementation details
• Discussion of alternatives considered
• References and supporting information

Types of PEPs

PEPs fall into three categories:

1. Standards Track PEPs: Propose new features for Python itself
2. Informational PEPs: Describe Python design issues or guidelines
3. Process PEPs: Propose changes to Python’s development process

PEP Impact

Fundamental Python features started as PEPs:

• PEP 8 established Python’s style guidelines
• PEP 484 introduced type hints
• PEP 517/518 modernized Python’s packaging infrastructure
• PEP 621 standardized project metadata in pyproject.toml