Python’s Steering Council

There are several references in this PEP to the “Steering Council” or “Council”. This refers to the current members of the elected Steering Council described in PEP 13, in their role as the final authorities on whether or not PEPs will be accepted or rejected.

Python’s Core Developers

There are several references in this PEP to “core developers”. This refers to the currently active Python core team members described in PEP 13.

Python’s BDFL

Previous versions of this PEP used the title “BDFL-Delegate” for PEP decision makers. This was a historical reference to Python’s previous governance model, where all design authority ultimately derived from Guido van Rossum, the original creator of the Python programming language. By contrast, the Steering Council’s design authority derives from their election by the currently active core developers. Now, PEP-Delegate is used in place of BDFL-Delegate.

PEP Editors

The PEP editors are individuals responsible for managing the administrative and editorial aspects of the PEP workflow (e.g. assigning PEP numbers and changing their status). See PEP Editor Responsibilities & Workflow for details.

PEP editorship is by invitation of the current editors, and they can be contacted by mentioning @python/pep-editors on GitHub. All of the PEP workflow can be conducted via the GitHub PEP repository issues and pull requests.

Start with an idea for Python

The PEP process begins with a new idea for Python. It is highly recommended that a single PEP contain a single key proposal or new idea; the more focused the PEP, the more successful it tends to be. Most enhancements and bug fixes don’t need a PEP and can be submitted directly to the Python issue tracker. The PEP editors reserve the right to reject PEP proposals if they appear too unfocused or too broad. If in doubt, split your PEP into several well-focused ones.

Each PEP must have a champion – someone who writes the PEP using the style and format described below, shepherds the discussions in the appropriate forums, and attempts to build community consensus around the idea. The PEP champion (a.k.a. Author) should first attempt to ascertain whether the idea is PEP-able. Posting to the Ideas category of the Python Discourse is usually the best way to go about this, unless a more specialized venue is appropriate, such as the Typing category (for static typing ideas) or Packaging category (for packaging ideas) on the Python Discourse.

Vetting an idea publicly before going as far as writing a PEP is meant to save the potential author time. Many ideas have been brought forward for changing Python that have been rejected for various reasons. Asking the Python community first if an idea is original helps prevent too much time being spent on something that is guaranteed to be rejected based on prior discussions (searching the internet does not always do the trick). It also helps to make sure the idea is applicable to the entire community and not just the author. Just because an idea sounds good to the author does not mean it will work for most people in most areas where Python is used.

Once the champion has asked the Python community as to whether an idea has any chance of acceptance, a draft PEP should be presented to the appropriate venue mentioned above. This gives the author a chance to flesh out the draft PEP to make properly formatted, of high quality, and to address initial concerns about the proposal.

Submitting a PEP

Following the above initial discussion, the workflow varies based on whether any of the PEP’s co-authors are core developers. If one or more of the PEP’s co-authors are core developers, they are responsible for following the process outlined below. Otherwise (i.e. none of the co-authors are core developers), then the PEP author(s) will need to find a sponsor for the PEP.

Ideally, a core developer sponsor is identified, but non-core sponsors may also be selected with the approval of the Steering Council. Members of the GitHub “PEP editors” team and members of the Typing Council (PEP 729) are pre-approved to be sponsors. The sponsor’s job is to provide guidance to the PEP author to help them through the logistics of the PEP process (somewhat acting like a mentor). Being a sponsor does not disqualify that person from becoming a co-author or PEP-Delegate later on (but not both). The sponsor of a PEP is recorded in the “Sponsor:” field of the header.

Once the sponsor or the core developer(s) co-authoring the PEP deem the PEP ready for submission, the proposal should be submitted as a draft PEP via a GitHub pull request. The draft must be written in PEP style as described below, else it will fail review immediately (although minor errors may be corrected by the editors).

The standard PEP workflow is:

• You, the PEP author, fork the PEP repository, and create a file named pep-NNNN.rst that contains your new PEP. NNNN should be the next available PEP number not used by a published or in-PR PEP.
• In the “PEP:” header field, enter the PEP number that matches your filename as your draft PEP number.
• In the “Type:” header field, enter “Standards Track”, “Informational”, or “Process” as appropriate, and for the “Status:” field enter “Draft”. For full details, see PEP Header Preamble.
• Update .github/CODEOWNERS such that any co-author(s) or sponsors with write access to the PEP repository are listed for your new file. This ensures any future pull requests changing the file will be assigned to them.
• Push this to your GitHub fork and submit a pull request.
• The PEP editors review your PR for structure, formatting, and other errors. For a reST-formatted PEP, PEP 12 is provided as a template. It also provides a complete introduction to reST markup that is used in PEPs. Approval criteria are:
  • It is sound and complete. The ideas must make technical sense. The editors do not consider whether they seem likely to be accepted.
  • The title accurately describes the content.
  • The PEP’s language (spelling, grammar, sentence structure, etc.) and code style (examples should match PEP 7 & PEP 8) should be correct and conformant. The PEP text will be automatically checked for correct reStructuredText formatting when the pull request is submitted. PEPs with invalid reST markup will not be approved.

  Editors are generally quite lenient about this initial review, expecting that problems will be corrected by the reviewing process. Note: Approval of the PEP is no guarantee that there are no embarrassing mistakes! Correctness is the responsibility of authors and reviewers, not the editors.

  If the PEP isn’t ready for approval, an editor will send it back to the author for revision, with specific instructions.

• Once approved, they will assign your PEP a number.

Once the review process is complete, and the PEP editors approve it (note that this is not the same as accepting your PEP!), they will squash commit your pull request onto main.

The PEP editors will not unreasonably deny publication of a PEP. Reasons for denying PEP status include duplication of effort, being technically unsound, not providing proper motivation or addressing backwards compatibility, or not in keeping with the Python philosophy. The Steering Council can be consulted during the approval phase, and are the final arbiter of a draft’s PEP-ability.

Developers with write access to the PEP repository may claim PEP numbers directly by creating and committing a new PEP. When doing so, the developer must handle the tasks that would normally be taken care of by the PEP editors (see PEP Editor Responsibilities & Workflow). This includes ensuring the initial version meets the expected standards for submitting a PEP. Alternately, even developers should submit PEPs via pull request. When doing so, you are generally expected to handle the process yourself; if you need assistance from PEP editors, mention @python/pep-editors on GitHub.

As updates are necessary, the PEP author can check in new versions if they (or a collaborating developer) have write access to the PEP repository. Getting a PEP number assigned early can be useful for ease of reference, especially when multiple draft PEPs are being considered at the same time.

Standards Track PEPs consist of two parts, a design document and a reference implementation. It is generally recommended that at least a prototype implementation be co-developed with the PEP, as ideas that sound good in principle sometimes turn out to be impractical when subjected to the test of implementation.

Discussing a PEP

As soon as a PEP number has been assigned and the draft PEP is committed to the PEP repository, a discussion thread for the PEP should be created to provide a central place to discuss and review its contents, and the PEP should be updated so that the Discussions-To header links to it.

The PEP authors (or sponsor, if applicable) may select any reasonable venue for the discussion, so long as the the following criteria are met:

• The forum is appropriate to the PEP’s topic.
• The thread is publicly available on the web so that all interested parties can participate.
• The discussion is subject to the Python Community Code of Conduct.
• A direct link to the current discussion thread is provided in the PEP under the Discussions-To header.

The PEPs category of the Python Discourse is the preferred choice for most new PEPs, whereas historically the Python-Dev mailing list was commonly used. Some specialized topics have specific venues, such as the Typing category and the Packaging category on the Python Discourse for typing and packaging PEPs, respectively. If the PEP authors are unsure of the best venue, the PEP Sponsor and PEP editors can advise them accordingly.

If a PEP undergoes a significant re-write or other major, substantive changes to its proposed specification, a new thread should typically be created in the chosen venue to solicit additional feedback. If this occurs, the Discussions-To link must be updated and a new Post-History entry added pointing to this new thread.

If it is not chosen as the discussion venue, a brief announcement post should be made to the PEPs category with at least a link to the rendered PEP and the Discussions-To thread when the draft PEP is committed to the repository and if a major-enough change is made to trigger a new thread.

PEP authors are responsible for collecting community feedback on a PEP before submitting it for review. However, to avoid long-winded and open-ended discussions, strategies such as soliciting private or more narrowly-tailored feedback in the early design phase, collaborating with other community members with expertise in the PEP’s subject matter, and picking an appropriately-specialized discussion for the PEP’s topic (if applicable) should be considered. PEP authors should use their discretion here.

Once the PEP is assigned a number and committed to the PEP repository, substantive issues should generally be discussed on the canonical public thread, as opposed to private channels, GitHub pull request reviews or unrelated venues. This ensures everyone can follow and contribute, avoids fragmenting the discussion, and makes sure it is fully considered as part of the PEP review process. Comments, support, concerns and other feedback on this designated thread are a critical part of what the Steering Council or PEP-Delegate will consider when reviewing the PEP.

PEP Review & Resolution

Once the authors have completed a PEP, they may request a review for style and consistency from the PEP editors. However, content review and acceptance of the PEP is ultimately the responsibility of the Steering Council, which is formally initiated by opening a Steering Council issue once the authors (and sponsor, if any) determine the PEP is ready for final review and resolution.

To expedite the process in selected cases (e.g. when a change is clearly beneficial and ready to be accepted, but the PEP hasn’t been formally submitted for review yet), the Steering Council may also initiate a PEP review, first notifying the PEP author(s) and giving them a chance to make revisions.

The final authority for PEP approval is the Steering Council. However, whenever a new PEP is put forward, any core developer who believes they are suitably experienced to make the final decision on that PEP may offer to serve as its PEP-Delegate by notifying the Steering Council of their intent. If the Steering Council approves their offer, the PEP-Delegate will then have the authority to approve or reject that PEP. For PEPs related to the Python type system, the Typing Council (PEP 729) provides a recommendation to the Steering Council. To request such a recommendation, open an issue on the Typing Council issue tracker.

The term “PEP-Delegate” is used under the Steering Council governance model for the PEP’s designated decision maker, who is recorded in the “PEP-Delegate” field in the PEP’s header. The term “BDFL-Delegate” is a deprecated alias for PEP-Delegate, a legacy of the time when when Python was led by a BDFL. Any legacy references to “BDFL-Delegate” should be treated as equivalent to “PEP-Delegate”.

An individual offering to nominate themselves as a PEP-Delegate must notify the relevant authors and (when present) the sponsor for the PEP, and submit their request to the Steering Council (which can be done via a new issue ). Those taking on this responsibility are free to seek additional guidance from the Steering Council at any time, and are also expected to take the advice and perspectives of other core developers into account.

The Steering Council will generally approve such self-nominations by default, but may choose to decline them. Possible reasons for the Steering Council declining a self-nomination as PEP-Delegate include, but are not limited to, perceptions of a potential conflict of interest (e.g. working for the same organisation as the PEP submitter), or simply considering another potential PEP-Delegate to be more appropriate. If core developers (or other community members) have concerns regarding the suitability of a PEP-Delegate for any given PEP, they may ask the Steering Council to review the delegation.

If no volunteer steps forward, then the Steering Council will approach core developers (and potentially other Python community members) with relevant expertise, in an attempt to identify a candidate that is willing to serve as PEP-Delegate for that PEP. If no suitable candidate can be found, then the PEP will be marked as Deferred until one is available.

Previously appointed PEP-Delegates may choose to step down, or be asked to step down by the Council, in which case a new PEP-Delegate will be appointed in the same manner as for a new PEP (including deferral of the PEP if no suitable replacement can be found). In the event that a PEP-Delegate is asked to step down, this will overrule any prior acceptance or rejection of the PEP, and it will revert to Draft status.

When such standing delegations are put in place, the Steering Council will maintain sufficient public records to allow subsequent Councils, the core developers, and the wider Python community to understand the delegations that currently exist, why they were put in place, and the circumstances under which they may no longer be needed.

For a PEP to be accepted it must meet certain minimum criteria. It must be a clear and complete description of the proposed enhancement. The enhancement must represent a net improvement. The proposed implementation, if applicable, must be solid and must not complicate the interpreter unduly. Finally, a proposed enhancement must be “pythonic” in order to be accepted by the Steering Council. (However, “pythonic” is an imprecise term; it may be defined as whatever is acceptable to the Steering Council. This logic is intentionally circular.) See PEP 2 for standard library module acceptance criteria.

Except where otherwise approved by the Steering Council, pronouncements of PEP resolution will be posted to the PEPs category on the Python Discourse.

Once a PEP has been accepted, the reference implementation must be completed. When the reference implementation is complete and incorporated into the main source code repository, the status will be changed to “Final”.

To allow gathering of additional design and interface feedback before committing to long term stability for a language feature or standard library API, a PEP may also be marked as “Provisional”. This is short for “Provisionally Accepted”, and indicates that the proposal has been accepted for inclusion in the reference implementation, but additional user feedback is needed before the full design can be considered “Final”. Unlike regular accepted PEPs, provisionally accepted PEPs may still be Rejected or Withdrawn even after the related changes have been included in a Python release.

Wherever possible, it is considered preferable to reduce the scope of a proposal to avoid the need to rely on the “Provisional” status (e.g. by deferring some features to later PEPs), as this status can lead to version compatibility challenges in the wider Python ecosystem. PEP 411 provides additional details on potential use cases for the Provisional status.

A PEP can also be assigned the status “Deferred”. The PEP author or an editor can assign the PEP this status when no progress is being made on the PEP. Once a PEP is deferred, a PEP editor can reassign it to draft status.

A PEP can also be “Rejected”. Perhaps after all is said and done it was not a good idea. It is still important to have a record of this fact. The “Withdrawn” status is similar - it means that the PEP author themselves has decided that the PEP is actually a bad idea, or has accepted that a competing proposal is a better alternative.

When a PEP is Accepted, Rejected or Withdrawn, the PEP should be updated accordingly. In addition to updating the Status field, at the very least the Resolution header should be added with a direct link to the relevant post making a decision on the PEP.

PEPs can also be superseded by a different PEP, rendering the original obsolete. This is intended for Informational PEPs, where version 2 of an API can replace version 1.

The possible paths of the status of PEPs are as follows:

While not shown in the diagram, “Accepted” PEPs may technically move to “Rejected” or “Withdrawn” even after acceptance. This will only occur if the implementation process reveals fundamental flaws in the design that were not noticed prior to acceptance of the PEP. Unlike Provisional PEPs, these transitions are only permitted if the accepted proposal has not been included in a Python release - released changes must instead go through the regular deprecation process (which may require a new PEP providing the rationale for the deprecation).

Some Informational and Process PEPs may also have a status of “Active” if they are never meant to be completed. E.g. PEP 1 (this PEP).

PEP Maintenance

In general, PEPs are no longer substantially modified after they have reached the Accepted, Final, Rejected or Superseded state. Once resolution is reached, a PEP is considered a historical document rather than a living specification. Formal documentation of the expected behavior should be maintained elsewhere, such as the Language Reference for core features, the Library Reference for standard library modules or the PyPA Specifications for packaging.

If changes based on implementation experience and user feedback are made to Standards track PEPs while in the Provisional or (with SC approval) Accepted state, they should be noted in the PEP, such that the PEP accurately describes the implementation at the point where it is marked Final.

Active (Informational and Process) PEPs may be updated over time to reflect changes to development practices and other details. The precise process followed in these cases will depend on the nature and purpose of the PEP in question.

Occasionally, a Deferred or even a Withdrawn PEP may be resurrected with major updates, but it is often better to just propose a new one.