Release date: June 17, 2021

This is a beta preview of Python 3.10

Python 3.10 is still in development. 3.10.0b3 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.

We strongly encourage maintainers of third-party Python projects to test with 3.10 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 (Monday, 2021-08-02). Our goal is to have no ABI changes after beta 4 and as few code changes as possible after 3.10.0rc1, the first release candidate. To achieve that, it will be extremely important to get as much exposure for 3.10 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.

Major new features of the 3.10 series, compared to 3.9

Many new features for Python 3.10 are still being planned and written. Among the new major new features and changes so far:

• PEP 623 -- Deprecate and prepare for the removal of the wstr member in PyUnicodeObject.
• PEP 604 -- Allow writing union types as X | Y
• PEP 612 -- Parameter Specification Variables
• PEP 626 -- Precise line numbers for debugging and other tools.
• PEP 618 -- Add Optional Length-Checking To zip.
• bpo-12782: Parenthesized context managers are now officially allowed.
• PEP 632 -- Deprecate distutils module.
• PEP 613 -- Explicit Type Aliases
• PEP 634 -- Structural Pattern Matching: Specification
• PEP 635 -- Structural Pattern Matching: Motivation and Rationale
• PEP 636 -- Structural Pattern Matching: Tutorial
• PEP 644 -- Require OpenSSL 1.1.1 or newer
• PEP 624 -- Remove Py_UNICODE encoder APIs

• PEP 597 -- Add optional EncodingWarning

• (Hey, fellow core developer, if a feature you find important is missing from this list, let Pablo know.)

The next pre-release of Python 3.10 will be 3.10.0b4, currently scheduled for Saturday, 2021-07-10.

bpo-38605: from __future__ import annotations (PEP 563) used to be on this list in previous pre-releases but it has been postponed to Python 3.11 due to some compatibility concerns. You can read the Steering Council communication about it here to learn more.

More resources

• Changelog
• Online Documentation
• PEP 619, 3.10 Release Schedule
• Report bugs at https://bugs.python.org.
• Help fund Python and its community.

And now for something completely different

There are no green stars. Why? In general, objects don't emit a single wavelength of light when they shine. Instead, they emit photons in a range of wavelengths. If you were to use some sort of detector that is sensitive to the wavelengths of light emitted by an object, and then plotted the number of them versus wavelength, you get a lopsided plot called a blackbody curve. For an object as hot as the Sun, that curve peaks at blue-green, so it emits most of its photons there. But it still emits some that are bluer, and some that are redder. When we look at the Sun, we see all these colors blended together. Our eyes mix them up to produce one color: white. A warmer star will put out more blue, and a cooler one redder, but no matter what, our eyes just won't see that as green. Due to how we perceive color, the only way to see a star as being green is for it to be only emitting green light. But as starts always emit radiation following the blackbody curve, that's pretty much impossible.