Python 3.8.0b3 available for testing

This time without delays, I present you Python 3.8.0b3:

This release is the third of four planned beta release previews. Beta release previews are intended to give the wider community the opportunity to test new features and bug fixes and to prepare their projects to support the new feature release. The next pre-release of Python 3.8 will be 3.8.0b4, the last beta release, currently scheduled for 2019-08-26.

Call to action

We strongly encourage maintainers of third-party Python projects to test with 3.8 during the beta phase and report issues found to the Python bug tracker as soon as possible. While the release is planned to be feature complete entering the beta phase, it is possible that features may be modified or, in rare cases, deleted up until the start of the release candidate phase (2019-09-30). Our goal is have no ABI changes after beta 3 and no code changes after 3.8.0rc1, the release candidate. To achieve that, it will be extremely important to get as much exposure for 3.8 as possible during the beta phase.

Please keep in mind that this is a preview release and its use is not recommended for production environments.

Last beta coming

Beta 4 can only be released if all “Release blocker” and “Deferred blocker” issues on for 3.8.0 are resolved. Please prioritize those for the next four weeks.


Thanks to our binary builders, Ned and Steve, who were very quick today to get the macOS and Windows installers ready. The Windows story in particular got pretty magical, it’s now really fully automatic end-to-end.

Thanks to Victor for vastly improving the reliability of multiprocessing tests since Beta 2.

Thanks to Pablo for keeping the buildbots green.


Yay! Thanks. I’ve pushed an update to the docker images repository for 3.8b3.

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The 3.8.0b3 release is not currently listed on the front page of Also, the b2 link has scrolled off of the Latest News section. The purpose of beta releases is to garner user feedback on APIs, docs, and performance while there is still time to take corrective action. If we want real feedback, we need to make the beta releases much more prominent and actively solicit feedback. Right now, it doesn’t seem like we’re getting any benefit from a having four beta releases.

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Thanks for noticing, @rhettinger. If you see issues like that, it’s fastest to contact or nosy the release manager for the release, in this case @ambv; release managers are responsible for updating the web site information about new releases.

Thanks Ned. Hopefully, the 3.8.0b3 announcement can get posted on this week. Right now, it’s still missing.

Also, I’m hoping the other core devs will encourage people to start using the beta in earnest. We need validation of whether the new SyntaxWarning is as problematic for users as it has been for me and my clients.

How is this being done right now? Is there any way to automate this process?

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It’s done manually by the release managers and is not in need of automation. I’ve pinged @ambv but he seems to be away right now. If I don’t hear back from him soon, I’ll put something out there.

Sorry, I had house guests for a few days. I did miss the blog post this time around. This is now fixed.

There’s fortunately more channels through which Python beta releases are announced, like the mailing lists, Discourse, and Twitter. We should make some noise about testing the beta at PyBay, too, @rhettinger.