NXEP 0 — Purpose and Process


Jarrod Millman <millman@berkeley.edu>







What is a NXEP?

NXEP stands for NetworkX Enhancement Proposal. NXEPs are the primary mechanisms for proposing major new features, for collecting community input on an issue, and for documenting the design decisions that have gone into NetworkX. A NXEP should provide a concise technical specification of the feature and a rationale for the feature. The NXEP author is responsible for building consensus within the community and documenting dissenting opinions.

Because the NXEPs are maintained as text files in a versioned repository, their revision history is the historical record of the feature proposal 1.


There are three kinds of NXEPs:

  1. A Standards Track NXEP describes a new feature or implementation for NetworkX.

  2. An Informational NXEP describes a NetworkX design issue, or provides general guidelines or information to the Python community, but does not propose a new feature. Informational NXEPs do not necessarily represent a NetworkX community consensus or recommendation, so users and implementers are free to ignore Informational NXEPs or follow their advice.

  3. A Process NXEP describes a process surrounding NetworkX, or proposes a change to (or an event in) a process. Process NXEPs are like Standards Track NXEPs but apply to areas other than the NetworkX language itself. They may propose an implementation, but not to NetworkX’s codebase; they require community consensus. Examples include procedures, guidelines, changes to the decision-making process, and changes to the tools or environment used in NetworkX development. Any meta-NXEP is also considered a Process NXEP.

NXEP Workflow

The NXEP process begins with a new idea for NetworkX. It is highly recommended that a single NXEP contain a single key proposal or new idea. Small enhancements or patches often don’t need a NXEP and can be injected into the NetworkX development workflow with a pull request to the NetworkX repo. The more focused the NXEP, the more successful it tends to be. If in doubt, split your NXEP into several well-focused ones.

Each NXEP must have a champion—someone who writes the NXEP using the style and format described below, shepherds the discussions in the appropriate forums, and attempts to build community consensus around the idea. The NXEP champion (a.k.a. Author) should first attempt to ascertain whether the idea is suitable for a NXEP. Posting to the networkx-discussion mailing list is the best way to go about doing this.

The proposal should be submitted as a draft NXEP via a GitHub pull request to the doc/nxeps directory with the name nxep-<n>.rst where <n> is an appropriately assigned four-digit number (e.g., nxep-0000.rst). The draft must use the NXEP X — Template and Instructions file.

Once the PR for the NXEP is in place, a post should be made to the mailing list containing the sections up to “Backward compatibility”, with the purpose of limiting discussion there to usage and impact. Discussion on the pull request will have a broader scope, also including details of implementation.

At the earliest convenience, the PR should be merged (regardless of whether it is accepted during discussion). Additional PRs may be made by the Author to update or expand the NXEP, or by maintainers to set its status, discussion URL, etc.

Standards Track NXEPs 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 NXEP, as ideas that sound good in principle sometimes turn out to be impractical when subjected to the test of implementation. Often it makes sense for the prototype implementation to be made available as PR to the NetworkX repo (making sure to appropriately mark the PR as a WIP).

Review and Resolution

NXEPs are discussed on the mailing list. The possible paths of the status of NXEPs are as follows:


All NXEPs should be created with the Draft status.

Eventually, after discussion, there may be a consensus that the NXEP should be accepted – see the next section for details. At this point the status becomes Accepted.

Once a NXEP 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 NXEP 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 NXEPs, provisionally accepted NXEPs 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 NXEPs), as this status can lead to version compatibility challenges in the wider NetworkX ecosystem.

A NXEP can also be assigned status Deferred. The NXEP author or a core developer can assign the NXEP this status when no progress is being made on the NXEP.

A NXEP 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 NXEP author themselves has decided that the NXEP is actually a bad idea, or has accepted that a competing proposal is a better alternative.

When a NXEP is Accepted, Rejected, or Withdrawn, the NXEP should be updated accordingly. In addition to updating the status field, at the very least the Resolution header should be added with a link to the relevant thread in the mailing list archives.

NXEPs can also be Superseded by a different NXEP, rendering the original obsolete. The Replaced-By and Replaces headers should be added to the original and new NXEPs respectively.

Process NXEPs may also have a status of Active if they are never meant to be completed, e.g. NXEP 0 (this NXEP).

How a NXEP becomes Accepted

A NXEP is Accepted by consensus of all interested contributors. We need a concrete way to tell whether consensus has been reached. When you think a NXEP is ready to accept, send an email to the networkx-discussion mailing list with a subject like:

Proposal to accept NXEP #<number>: <title>

In the body of your email, you should:

  • link to the latest version of the NXEP,

  • briefly describe any major points of contention and how they were resolved,

  • include a sentence like: “If there are no substantive objections within 7 days from this email, then the NXEP will be accepted; see NXEP 0 for more details.”

For an example, see: https://mail.python.org/pipermail/networkx-discussion/2018-June/078345.html

After you send the email, you should make sure to link to the email thread from the Discussion section of the NXEP, so that people can find it later.

Generally the NXEP author will be the one to send this email, but anyone can do it – the important thing is to make sure that everyone knows when a NXEP is on the verge of acceptance, and give them a final chance to respond. If there’s some special reason to extend this final comment period beyond 7 days, then that’s fine, just say so in the email. You shouldn’t do less than 7 days, because sometimes people are travelling or similar and need some time to respond.

In general, the goal is to make sure that the community has consensus, not provide a rigid policy for people to try to game. When in doubt, err on the side of asking for more feedback and looking for opportunities to compromise.

If the final comment period passes without any substantive objections, then the NXEP can officially be marked Accepted. You should send a followup email notifying the list (celebratory emoji optional but encouraged 🎉✨), and then update the NXEP by setting its :Status: to Accepted, and its :Resolution: header to a link to your followup email.

If there are substantive objections, then the NXEP remains in Draft state, discussion continues as normal, and it can be proposed for acceptance again later once the objections are resolved.

In unusual cases, disagreements about the direction or approach may require escalation to the NetworkX Steering Council who then decide whether a controversial NXEP is Accepted.


In general, Standards track NXEPs are no longer modified after they have reached the Final state as the code and project documentation are considered the ultimate reference for the implemented feature. However, finalized Standards track NXEPs may be updated as needed.

Process NXEPs 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 NXEP being updated.

Format and Template

NXEPs are UTF-8 encoded text files using the reStructuredText format. Please see the NXEP X — Template and Instructions file and the reStructuredTextPrimer for more information. We use Sphinx to convert NXEPs to HTML for viewing on the web 2.

Header Preamble

Each NXEP must begin with a header preamble. The headers must appear in the following order. Headers marked with * are optional. All other headers are required.

  :Author: <list of authors' real names and optionally, email addresses>
  :Status: <Draft | Active | Accepted | Deferred | Rejected |
           Withdrawn | Final | Superseded>
  :Type: <Standards Track | Process>
  :Created: <date created on, in dd-mmm-yyyy format>
* :Requires: <nxep numbers>
* :NetworkX-Version: <version number>
* :Replaces: <nxep number>
* :Replaced-By: <nxep number>
* :Resolution: <url>

The Author header lists the names, and optionally the email addresses of all the authors of the NXEP. The format of the Author header value must be

Random J. User <address@dom.ain>

if the email address is included, and just

Random J. User

if the address is not given. If there are multiple authors, each should be on a separate line.

References and Footnotes


This historical record is available by the normal git commands for retrieving older revisions, and can also be browsed on GitHub.


The URL for viewing NXEPs on the web is https://networkx.org/documentation/latest/developer/nxeps/index.html