14. How to Become a Core Developer


This is the merge of the hg-era Jython devguide with the current CPython devguide.

14.1. What it Takes

When you have consistently contributed patches which meet quality standards without requiring extensive rewrites prior to being committed, you may qualify for commit privileges and become a core developer of Jython. You must also work well with other core developers (and people in general) as you become an ambassador for the Jython project.

Typically a core developer will offer you the chance to gain commit privilege. The person making the offer will become your mentor and watch your commits for a while to make sure you understand the development process. If other core developers agree that you should gain commit privileges you are then extended an official offer.

14.2. What it Means

As contributors to the CPython project, our shared responsibility is to collaborate constructively with other contributors, including core developers. This responsibility covers all forms of contribution, whether that’s submitting patches to the implementation or documentation, reviewing other peoples’ patches, triaging issues on the issue tracker, or discussing design and development ideas on the core mailing lists.

Core developers accept key additional responsibilities around the ongoing management of the project:

  • core developers bear the additional responsibility of handling the consequences of accepting a change into the code base or documentation. That includes reverting or fixing it if it causes problems in the Buildbot fleet or someone spots a problem in post-commit review, as well as helping out the release manager in resolving any problems found during the pre-release testing cycle. While all contributors are free to help out with this part of the process, and it is most welcome when they do, the actual responsibility rests with the core developer that merged the change

  • core developers also bear the primary responsibility for deciding when changes proposed on the issue tracker should be escalated to python-ideas or python-dev for wider discussion, as well as suggesting the use of the Python Enhancement Proposal process to manage the design and justification of complex changes, or changes with a potentially significant impact on end users

As a result of the additional responsibilities they accept, core developers gain the privilege of being able to approve proposed changes, as well as being able to reject them as inappropriate. Core developers are also able to request that even already merged changes be escalated to python-dev for further discussion, and potentially even reverted prior to release.

Becoming a core developer isn’t a binary “all-or-nothing” status - CPython is a large project, and different core developers accept responsibility for making design and development decisions in different areas (as documented in the Experts Index and Developer Log).

14.3. Gaining Commit Privileges

When you have been extended an official offer to become a Jython core developer, there are several things you must do.

14.3.1. Mailing Lists

You are expected to subscribe to jython-dev, jython-checkins, and jython-bugs. See Following Python’s Development for links to these mailing lists.

14.3.2. Issue Tracker

If you did not gain the Developer role in the Jython issue tracker before gaining commit privileges, please say so. This will allow issues to be assigned to you. A tracker admin should also flip your “is committer” bit in the tracker’s account screen.

It is expected that on the issue tracker you have a username in the form of “first_name.last_name”. If your initial issue tracker username is not of this form, please change it. This is so that it is easier to assign issues to the right person.

14.3.3. SSH (Mercurial)

You need to generate an SSH 2 RSA key to be able to commit code. You may have multiple keys if you wish (e.g., for work and home). Send your key as an attachment in an email to hgaccounts@python.org. Help in generating an SSH key can be found in the Jython Developer FAQ.

Your SSH key will be set to a username in the form of “first_name.last_name”. This should match your username on the issue tracker.

You can verify your commit access by looking at http://hg.python.org/committers.txt which lists all core developers by username. If you want to practice, there is a test repository where you can freely commit and push any changes you like:

hg clone ssh://hg@hg.python.org/test/ hgtest

14.3.4. GitHub

You will be added to the Jython core team on GitHub. This will give you rights to commit to various repositories under the Jython organization on GitHub. When you are initially added you will be emailed by GitHub with an invitation to join the team. Please accept the invite in the email or go to https://github.com/jython and accept the invite there.

An entry in the Developer Log should also be entered for you. Typically the person who sponsored your application to become a core developer makes sure an entry is created for you.

14.3.5. Sign a Contributor Agreement

Submitting a contributor form for Python licenses any code you contribute to the Python Software Foundation. While you retain the copyright, giving the PSF the ability to license your code means it can be put under the PSF license so it can be legally distributed with Python.

This is a very important step! Hopefully you have already submitted a contributor agreement if you have been submitting patches. But if you have not done this yet, it is best to do this ASAP, probably before you even do your first commit so as to not forget. Also do not forget to enter your GitHub username into your details on the issue tracker.

14.3.6. Read/Write Checkout (Mercurial)

With your commit privileges working and your contributor form submitted, you can now get a read/write checkout of the code. URLs for read/write checkouts are different than those for read-only checkouts as SSH is used instead of HTTP.

You can clone the repository (which contains all active branches) with:

hg clone ssh://hg@hg.python.org/jython

The default branch in that repository is the current development branch. You can of course switch your working copy to one of the maintenance branches, for example:

hg update 2.7

14.3.7. Pull Request merging (GitHub)

Once you have your commit privileges on GitHub you will be able to accept pull requests on GitHub. You should plan to continue to submit your own changes through pull requests as if you weren’t a core developer to benefit from various things such as automatic integration testing, but you can accept your own pull requests if you feel comfortable doing so.

14.4. Responsibilities

As a core developer, there are certain things that are expected of you.

First and foremost, be a good person. This might sound melodramatic, but you are now a member of the Jython project and thus represent the project and your fellow core developers whenever you discuss Jython with anyone. We have a reputation for being a very nice group of people and we would like to keep it that way. Core developers responsibilities include following the PSF Code of Conduct.

Second, please be prompt in responding to questions. Many contributors to Python are volunteers so what little free time they can dedicate to Python should be spent being productive. If you have been asked to respond to an issue or answer a question and you put it off it ends up stalling other people’s work. It is completely acceptable to say you are too busy, but you need to say that instead of leaving people waiting for an answer. This also applies to anything you do on the issue tracker.

Third, please list what areas you want to be considered an expert in the Experts Index. This allows triagers to direct issues to you which involve an area you are an expert in. But, as stated in the second point above, if you do not have the time to answer questions promptly then please remove yourself as needed from the file so that you will not be bothered in the future. Once again, we all understand how life gets in the way, so no one will be insulted if you remove yourself from the list.

Fourth, please consider whether or not you wish to add your name to the Core Developer Motivations and Affiliations list. Core contributor participation in the list helps the wider Python community to better appreciate the perspectives currently represented amongst the core development team, the Python Software Foundation to better assess the sustainability of current contributions to CPython core development, and also serves as a referral list for organisations seeking commercial Python support from the core development community.

And finally, enjoy yourself! Contributing to open source software should be fun (overall). If you find yourself no longer enjoying the work then either take a break or figure out what you need to do to make it enjoyable again.