Release Procedures

The current release procedure for Astropy involves a combination of an automated release script and some manual steps. Future versions will automate more of the process, if not all.

There are several different procedures below, depending on the situation:

For a signed release, see Creating a GPG Signing Key and a Signed Tag for relevant setup instructions.

Standard Release Procedure

This is the standard release procedure for releasing Astropy (or affiliated packages that use the full bugfix/maintenance branch approach.)

  1. Create a GitHub milestone for the next bugfix version, move any remaining issues from the version you are about to release, and close the milestone. When releasing a major release, close the last milestone on the previous maintenance branch, too.


    Creation of new milestone can be done as early as when you ping maintainers about their relevant pull requests, so that the maintainers have the option to re-milestone their work.

  2. If there are any issues in the GitHub issue tracker that are labeled affects-dev but are issues that apply to this release, update them to affects-release. Similarly, if any issues remain open for this release, re-assign them to the next relevant milestone.

  3. (Only for major versions) Make sure to update the “What’s new” section with the stats on the number of issues, PRs, and contributors. For the first two, the astropy-procedures repository script can provide the numbers since the last major release. For the final one, you will likely need to update the Astropy .mailmap file, as there are often contributors who are not careful about using the same e-mail address for every commit. The easiest way to do this is to run the command git shortlog -n -s -e to see the list of all contributors and their email addresses. Look for any misnamed entries or duplicates, and add them to the .mailmap file (matched to the appropriate canonical name/email address.) Once you have finished this, you can count the number of lines in git shortlog -s to get the final contributor count.

  4. Also be sure to update the docs/credits.rst file to include any new contributors from the above step. (This step is only required on major releases, but can be done for bugfix releases as time allows.)

  5. (astropy specific) Ensure the built-in IERS earth rotation parameter and leap second tables are up to date by changing directory to astropy/utils/iers/data and executing Check the result with git diff (do not be surprised to find many lines in the eopc04_IAU2000.62-now file change; those data are reanalyzed periodically) and committing.

  6. Ensure you have a GPG key pair available for when git needs to sign the tag you create for the release. See Creating a GPG Signing Key and a Signed Tag for more on this.

  7. Obtain a clean version of the astropy core repository. That is, one where you don’t have any intermediate build files. Either use a fresh git clone or do git clean -dfx.

  8. Be sure you’re on the branch appropriate for the version you’re about to release. For example, if releasing version 1.2.2 make sure to:

    $ git checkout v1.2.x
  9. Make sure that the continuous integration services (e.g., Travis or CircleCI) are passing for the astropy core repository branch you are going to release. Also check that the Azure core package pipeline which builds wheels on the v* branches is passing. You may also want to locally run the tests (with remote data on to ensure all of the tests actually run), using tox to do a thorough test in an isolated environment:

    $ pip install tox --upgrade
    $ TEST_READ_HUGE_FILE=1 tox -e test-alldeps -- --remote-data=any
  10. Edit the CHANGES.rst file by changing the date for the version you are about to release from “unreleased” to today’s date. Also be sure to remove any sections of the changelog for that version that have no entries. For releases that come after release candidates (Modifications for a beta/release candidate release), the title of the changelog section should be replaced too, thus getting rid of any mention of the release candidate. Then add and commit those changes with:

    <use your favorite editor on CHANGES.rst>
    $ git add CHANGES.rst
    $ git commit -m "Finalizing changelog for v<version>"
  11. Push the branch back to GitHub, e.g.:

    $ git push upstream v1.2.x

    and make sure that the CI services mentioned above (includnig the Azure pipeline) are still passing.


    You may need to replace upstream here with astropy or whatever remote name you use for the astropy core repository.

  12. Tag the commit with v<version>, being certain to sign the tag with the -s option:

    $ git tag -s v<version> -m "Tagging v<version>"
  13. Push up the tag to the astropy core repository:

    $ git push upstream v<tag version>


    You may need to replace upstream here with astropy or whatever remote name you use for the astropy core repository. Also, it might be tempting to use the --tags argument to git push, but this should not be done, as it might push up some unintended tags.

    At this point if all goes well, the wheels and sdist will be build in the Azure core package pipeline and uploaded to PyPI!

  14. In the event there are any issues with the wheel building for the tag (which shouldn’t really happen if it was passing for the release branch), you’ll have to fix whatever the problem is. First you will need to back out the release procedure by dropping the commits you made for release and removing the tag you created:

    $ git reset --hard HEAD^^^^ # you could also use the SHA hash of the commit before your first changelog edit
    $ git tag -d v<version>


    Any re-pushing the same tag back out to GitHub hereafter would be a force-push.

Once the sdist and wheels are uploaded, the release is done!

Congratulations! You have completed the release! Now there are just a few clean-up tasks to finalize the process.

Post-Release procedures

  1. Go back to release branch (e.g., 1.2.x) and update the CHANGES.rst file with a new section for the next version. Then add and commit:

    $ git checkout v1.2.x
    <use your favorite editor on CHANGES.rst>
    $ git add CHANGES.rst
    $ git commit -m "Add v<next_version> to the changelog"
  2. Push up these changes to the astropy core repository:

    $ git push upstream v<version branch>.x
  3. If this is a release of the current release (i.e., not an LTS supported along side a more recent version), update the “stable” branch to point to the new release:

    $ git checkout stable
    $ git reset --hard v<version>
    $ git push upstream stable --force
  4. Update Readthedocs so that it builds docs for the version you just released. You’ll find this in the “admin” tab, with checkboxes next to each github tag. Also verify that the stable Readthedocs version builds correctly for the new version (it should trigger automatically once you’ve done the previous step).

  5. When releasing a patch release, also set the previous RTD version in the release history to “protected”. For example when releasing v1.1.2, set v1.1.1 to “protected”. This prevents the previous releases from cluttering the list of versions that users see in the version dropdown (the previous versions are still accessible by their URL though).

  6. Update the Astropy web site by editing the index.html page at by changing the “current version” link and/or updating the list of older versions if this is an LTS bugfix or a new major version. You may also need to update the contributor list on the web site if you updated the docs/credits.rst at the outset.

  7. Open a PR to the astropy master branch to update the CHANGES.rst to reflect the date of the release you just performed and to include the new section of the changelog. Often the easiest way to do this is to use git cherry-pick the changelog commit just before the release commit from above. If you are not sure how to do this, you might be better off copying-and-pasting the relevant parts of the maintenance branch’s CHANGES.rst into master. In the same PR, you also have to update docs/whatsnew/index.rst and docs/whatsnew/X.Y.rst to link to “what’s new” documentation in the released RTD branch, using the existing text as example.

  8. conda-forge has a bot that automatically opens a PR from a new PyPI (stable) release, which you need to follow up on and merge. Meanwhile, for a LTS release, you still have to manually open a PR at astropy-feedstock. This is similar to the process for wheels. When the conda-forge package is ready, email the Anaconda maintainers about the release(s) so they can update the versions in the default channels. Typically, you should wait to make sure conda-forge and possibly conda works before sending out the public announcement (so that users who want to try out the new version can do so with conda).

  9. Update the LATEST_ASTROPY_STABLE or ASTROPY_LTS_VERSION variables in the ci-helpers repository once the conda packages became available.

  10. Upload the release to Zenodo. This has to be done manually since the Zenodo/GitHub integration relies on making releases on GitHub, which we don’t do. So for the Astropy core package, log in to Zenodo using the Astropy team credentials, then go to the existing record. Click on New version - note that it’s important to do this rather than upload the release as a completely new record. You should now see a pre-filled deposit form with the details from the previous release. Start off by removing the existing file under the Files section, then click on Choose Files and select the tar.gz release file for the core package release you are uploading, and click Start upload. Before you publish this, there are a few fields to update in the form: the Publication date should be set to the date the tar file was uploaded to PyPI, the Title should be updated to include the new version number, and the Version should be updated to include the version number (with no v prefix). Once you are happy with the changes, click Save, then Publish.

  11. Once the release(s) are available on the default conda channels, prepare the public announcement. Use the previous announcement as a template, but link to the release tag instead of stable. For a new major release, you should coordinate with the Astropy Coordinators. Meanwhile, for a bugfix release, you can proceed to send out an email to the astropy-dev and Astropy mailing lists.

Modifications for a beta/release candidate release

For major releases, we do beta and/or release candidates to have a chance to catch significant bugs before the true release. If the release you are performing is this kind of pre-release, some of the above steps need to be modified.

The primary modifications to the release procedure are:

  • When entering tagging the release, include a b? or rc?? suffix after the version number, e.g. “1.2b1” or “1.2rc1”. It is critical that you follow this numbering scheme (X.Yb# or X.Y.Zrc#), as it will ensure the release is ordered “before” the main release by various automated tools, and also tells PyPI that this is a “pre-release.”

  • Do not do steps in Post-Release procedures.

Once a release candidate is available, create a new Wiki page under Astropy Project Wiki with the title “vX.Y RC testing” (replace “X.Y” with the release number) using the wiki of a previous RC as a template.

Performing a Feature Freeze/Branching new Major Versions

As outlined in APE2, astropy releases occur at regular intervals, but feature freezes occur well before the actual release. Feature freezes are also the time when the master branch’s development separates from the new major version’s maintenance branch. This allows new development for the next major version to continue while the soon-to-be-released version can focus on bug fixes and documentation updates.

The procedure for this is straightforward:

  1. Update your local master branch to use to the latest version from github:

    $ git fetch upstream --tags
    $ git checkout -B master upstream/master
  2. Create a new branch from master at the point you want the feature freeze to occur:

    $ git branch v<version>.x
  3. Update the CHANGES.rst file with a new section at the very top for the next major version. Then add and commit those changes:

    <use your favorite editor on CHANGES.rst>
    $ git add CHANGES.rst
    $ git commit -m "Add <next_version> to changelog"
  4. Tag this commit using the next major version followed by .dev. For example, if you have just branched 4.0, create the tag on the commit adding the 4.1 section to the changelog:

    $ git tag -s "v<next_version>.dev" -m "Back to development: v<next_version>"
  5. Also update the “what’s new” section of the docs to include a section for the next major version. E.g.:

    $ cp docs/whatsnew/<current_version>.rst docs/whatsnew/<next_version>.rst

    You’ll then need to edit docs/whatsnew/<next_version>.rst, removing all the content but leaving the basic structure. You may also need to replace the “by the numbers” numbers with “xxx” as a reminder to update them before the next release. Then add the new version to the top of docs/whatsnew/index.rst, update the reference in docs/index.rst to point to the that version, and commit these changes

    $ git add docs/whatsnew/<next_version>.rst
    $ git add docs/whatsnew/index.rst
    $ git add docs/index.rst
    $ git commit -m "Added <next_version> whats new section"
  6. Push all of these changes up to github:

    $ git push upstream v<version>.x:v<version>.x
    $ git push upstream master:master


    You may need to replace upstream here with astropy or whatever remote name you use for the astropy core repository.

  7. On the github issue tracker, add a new milestone for the next major version.

Maintaining Bug Fix Releases


Always start with LTS release, followed by, if necessary, a bugfix for stable release. If the releases are not done in that order, the change log entries on what goes where can get mixed up.

Astropy releases, as recommended for most Python projects, follows a <major>.<minor>.<micro> version scheme, where the “micro” version is also known as a “bug fix” release. Bug fix releases should not change any user- visible interfaces. They should only fix bugs on the previous major/minor release and may also refactor internal APIs or include omissions from previous releases–that is, features that were documented to exist but were accidentally left out of the previous release. They may also include changes to docstrings that enhance clarity but do not describe new features (e.g., more examples, typo fixes, etc).

Bug fix releases are typically managed by maintaining one or more bug fix branches separate from the master branch (the release procedure below discusses creating these branches). Typically, whenever an issue is fixed on the Astropy master branch a decision must be made whether this is a fix that should be included in the Astropy bug fix release. Usually the answer to this question is “yes”, though there are some issues that may not apply to the bug fix branch. For example, it is not necessary to backport a fix to a new feature that did not exist when the bug fix branch was first created. New features are never merged into the bug fix branch–only bug fixes; hence the name.

In rare cases a bug fix may be made directly into the bug fix branch without going into the master branch first. This may occur if a fix is made to a feature that has been removed or rewritten in the development version and no longer has the issue being fixed. However, depending on how critical the bug is it may be worth including in a bug fix release, as some users can be slow to upgrade to new major/micro versions due to API changes.

Issues are assigned to an Astropy release by way of the Milestone feature in the GitHub issue tracker. At any given time there are at least two versions under development: The next major/minor version, and the next bug fix release. For example, at the time of writing there are two release milestones open: v1.2.2 and v0.3.0. In this case, v1.2.2 is the next bug fix release and all issues that should include fixes in that release should be assigned that milestone. Any issues that implement new features would go into the v0.3.0 milestone–this is any work that goes in the master branch that should not be backported. For a more detailed set of guidelines on using milestones, see Using Milestones and Labels.

Backporting fixes from master


The changelog script in astropy-procedures (pr_consistency scripts in particular) does not know about minor releases, thus please be careful. For example, let’s say we have two branches (master and v1.2.x). Both 1.2.0 and 1.2.1 releases will come out of the same v1.2.x branch. If a PR for 1.2.1 is merged into master before 1.2.0 is released, it should not be backported into v1.2.x branch until after 1.2.0 is released, despite complaining from the aforementioned script. This situation only arises in a very narrow time frame after 1.2.0 freeze but before its release.

Most fixes are backported using the git cherry-pick command, which applies the diff from a single commit like a patch. For the sake of example, say the current bug fix branch is ‘v1.2.x’, and that a bug was fixed in master in a commit abcd1234. In order to backport the fix, checkout the v1.2.x branch (it’s also good to make sure it’s in sync with the astropy core repository) and cherry-pick the appropriate commit:

$ git checkout v1.2.x
$ git pull upstream v1.2.x
$ git cherry-pick abcd1234

Sometimes a cherry-pick does not apply cleanly, since the bug fix branch represents a different line of development. This can be resolved like any other merge conflict: Edit the conflicted files by hand, and then run git commit and accept the default commit message. If the fix being cherry-picked has an associated changelog entry in a separate commit make sure to backport that as well.

What if the issue required more than one commit to fix? There are a few possibilities for this. The easiest is if the fix came in the form of a pull request that was merged into the master branch. Whenever GitHub merges a pull request it generates a merge commit in the master branch. This merge commit represents the full difference of all the commits in the pull request combined. What this means is that it is only necessary to cherry-pick the merge commit (this requires adding the -m 1 option to the cherry-pick command). For example, if 5678abcd is a merge commit:

$ git checkout v1.2.x
$ git pull upstream v1.2.x
$ git cherry-pick -m 1 5678abcd

In fact, because Astropy emphasizes a pull request-based workflow, this is the most common scenario for backporting bug fixes, and the one requiring the least thought. However, if you’re not dealing with backporting a fix that was not brought in as a pull request, read on.

See also

Merge commits and cherry picks for further explanation of the cherry-pick command and how it works with merge commits.

If not cherry-picking a merge commit there are still other options for dealing with multiple commits. The simplest, though potentially tedious, is to run the cherry-pick command once for each commit in the correct order. However, as of Git 1.7.2 it is possible to merge a range of commits like so:

$ git cherry-pick 1234abcd..56789def

This works fine so long as the commits you want to pick are actually congruous with each other. In most cases this will be the case, though some bug fixes will involve followup commits that need to back backported as well. Most bug fixes will have an issues associated with it in the issue tracker, so make sure to reference all commits related to that issue in the commit message. That way it’s harder for commits that need to be backported from getting lost.

Making fixes directly to the bug fix branch

As mentioned earlier in this section, in some cases a fix only applies to a bug fix release, and is not applicable in the mainline development. In this case there are two choices:

  1. An Astropy developer with commit access to the astropy core repository may check out the bug fix branch and commit and push your fix directly.

  2. Preferable: You may also make a pull request through GitHub against the bug fix branch rather than against master. Normally when making a pull request from a branch on your fork to the astropy core repository, GitHub compares your branch to Astropy’s master. If you look on the left-hand side of the pull request page, under “base repo: astropy/astropy” there is a drop-down list labeled “base branch: master”. You can click on this drop-down and instead select the bug fix branch (“v1.2.x” for example). Then GitHub will instead compare your fix against that branch, and merge into that branch when the PR is accepted.

Preparing the bug fix branch for release

There are two primary steps that need to be taken before creating a bug fix release. The rest of the procedure is the same as any other release as described in Standard Release Procedure (although be sure to provide the right version number).

  1. Any existing fixes to the issues assigned to a release milestone (and older LTS releases, if there are any), must be included in the maintenance branch before release.

  2. The Astropy changelog must be updated to list all issues–especially user-visible issues–fixed for the current release. The changelog should be updated in the master branch, and then merged into the bug fix branch. Most issues should already have changelog entries for them. But occasionally these are forgotten, so if doesn’t exist yet please add one in the process of backporting. See Updating and Maintaining the Changelog for more details.

To aid this process, there are a series of related scripts in the astropy-procedures repository, in the pr_consistency directory. These scripts essentially check that the above two conditions are met. Detailed documentation for these scripts is given in their repository, but here we summarize the basic workflow. Run the scripts in order (they are numbered 1.<something>.py, 2.<something>.py, etc.), entering your github login credentials as needed (if you are going to run them multiple times, using a ~/.netrc file is recommended - see this Stack Overflow post for more on how to do that, or a similar github help page). The script to actually check consistency should be run like:

$ python > consistency.html

Which will generate a simple web page that shows all of the areas where either a pull request was merged into master but is not in the relevant release that it has been milestoned for, as well as any changelog irregularities (i.e., PRs that are in the wrong section for what the github milestone indicates). You’ll want to correct those irregularities first before starting the backport process (re-running the scripts in order as needed).

The end of the consistency.html page will then show a series of git cherry-pick commands to update the maintenance branch with the PRs that are needed to make the milestones and branches consistent. Make sure you’re in the correct maintenance branch with e.g.,

$ git checkout v1.3.x
$ git pull upstream v1.3.x  # Or possibly a rebase if conflicts exist

if you are doing bugfixes for the 1.3.x series. Go through the commands one at a time, following the cherry-picking procedure described above. If for some reason you determine the github milestone was in error and the backporting is impossible, re-label the issue on github and move on. Also, whenever you backport a PR, it’s useful to leave a comment in the issue along the lines of “backported this to v1.3.x as <SHA>” so that it’s clear that the backport happened to others who might later look.


Automated scripts are never perfect, and can either miss issues that need to be backported, or in some cases can report false positives.

It’s always a good idea before finalizing a bug fix release to look on GitHub through the list of closed issues in the release milestone and check that each one has a fix in the bug fix branch. Usually a quick way to do this is for each issue to run:

$ git log --oneline <bugfix-branch> | grep #<issue>

Most fixes will mention their related issue in the commit message, so this tends to be pretty reliable. Some issues won’t show up in the commit log, however, as their fix is in a separate pull request. Usually GitHub makes this clear by cross-referencing the issue with its PR.

Finally, not all issues assigned to a release milestone need to be fixed before making that release. Usually, in the interest of getting a release with existing fixes out within some schedule, it’s best to triage issues that won’t be fixed soon to a new release milestone. If the upcoming bug fix release is ‘v1.2.2’, then go ahead and create a ‘v1.2.3’ milestone and reassign to it any issues that you don’t expect to be fixed in time for ‘v1.2.2’.

Creating a GPG Signing Key and a Signed Tag

One of the main steps in performing a release is to create a tag in the git repository representing the exact state of the repository that represents the version being released. For Astropy we will always use signed tags: A signed tag is annotated with the name and e-mail address of the signer, a date and time, and a checksum of the code in the tag. This information is then signed with a GPG private key and stored in the repository.

Using a signed tag ensures the integrity of the contents of that tag for the future. On a distributed VCS like git, anyone can create a tag of Astropy called “0.1” in their repository–and where it’s easy to monkey around even after the tag has been created. But only one “0.1” will be signed by one of the Astropy Project coordinators and will be verifiable with their public key.

Generating a public/private key pair

Git uses GPG to created signed tags, so in order to perform an Astropy release you will need GPG installed and will have to generated a signing key pair. Most *NIX installations come with GPG installed by default (as it is used to verify the integrity of system packages). If you don’t have the gpg command, consult the documentation for your system on how to install it.

For OSX, GPG can be installed from MacPorts using sudo port install gnupg.

To create a new public/private key pair, run:

$ gpg --gen-key

This will take you through a few interactive steps. For the encryption and expiry settings, it should be safe to use the default settings (I use a key size of 4096 just because what does a couple extra kilobytes hurt?) Enter your full name, preferably including your middle name or middle initial, and an e-mail address that you expect to be active for a decent amount of time. Note that this name and e-mail address must match the info you provide as your git configuration, so you should either choose the same name/e-mail address when you create your key, or update your git configuration to match the key info. Finally, choose a very good pass phrase that won’t be easily subject to brute force attacks.

If you expect to use the same key for some time, it’s good to make a backup of both your public and private key:

$ gpg --export --armor > public.key
$ gpg --export-secret-key --armor > private.key

Back up these files to a trusted location–preferably a write-once physical medium that can be stored safely somewhere. One may also back up their keys to a trusted online encrypted storage, though some might not find that secure enough–it’s up to you and what you’re comfortable with.

Add your public key to a keyserver

Now that you have a public key, you can publish this anywhere you like–in your e-mail, in a public code repository, etc. You can also upload it to a dedicated public OpenPGP keyserver. This will store the public key indefinitely (until you manually revoke it), and will be automatically synced with other keyservers around the world. That makes it easy to retrieve your public key using the gpg command-line tool.

To do this you will need your public key’s keyname. To find this enter:

$ gpg --list-keys

This will output something like:

pub   4096D/1234ABCD 2012-01-01
uid                  Your Name <your_email>
sub   4096g/567890EF 2012-01-01

The 8 digit hex number on the line starting with “pub”–in this example the “1234ABCD” unique keyname for your public key. To push it to a keyserver enter:

$ gpg --send-keys 1234ABCD

But replace the 1234ABCD with the keyname for your public key. Most systems come configured with a sensible default keyserver, so you shouldn’t have to specify any more than that.

Create a tag

Now test creating a signed tag in git. It’s safe to experiment with this–you can always delete the tag before pushing it to a remote repository:

$ git tag -s v0.1 -m "Astropy version 0.1"

This will ask for the password to unlock your private key in order to sign the tag with it. Confirm that the default signing key selected by git is the correct one (it will be if you only have one key).

Once the tag has been created, you can verify it with:

$ git tag -v v0.1

This should output something like:

object e8e3e3edc82b02f2088f4e974dbd2fe820c0d934
type commit
tag v0.1
tagger Your Name <your_email> 1339779534 -0400

Astropy version 0.1
gpg: Signature made Fri 15 Jun 2012 12:59:04 PM EDT using DSA key ID 0123ABCD
gpg: Good signature from "Your Name <your_email>"

You can use this to verify signed tags from any repository as long as you have the signer’s public key in your keyring. In this case you signed the tag yourself, so you already have your public key.

Note that if you are planning to do a release following the steps below, you will want to delete the tag you just created, because the release script does that for you. You can delete this tag by doing:

$ git tag -d v0.1