Release date: Dec. 8, 2021

This is an early developer preview of Python 3.11

Major new features of the 3.11 series, compared to 3.10

Python 3.11 is still in development. This release, 3.11.0a3 is the third of seven planned alpha releases.

Alpha releases are intended to make it easier to test the current state of new features and bug fixes and to test the release process.

During the alpha phase, features may be added up until the start of the beta phase (2022-05-06) and, if necessary, may be modified or deleted up until the release candidate phase (2022-08-01). Please keep in mind that this is a preview release and its use is not recommended for production environments.

Many new features for Python 3.11 are still being planned and written. Among the new major new features and changes so far:

• PEP 657 -- Include Fine-Grained Error Locations in Tracebacks
• PEP 654 -- Exception Groups and except*
• The Faster Cpython Project is already yielding some exciting results: this version of CPython 3.11 is ~ 19% faster on the geometric mean of the PyPerformance benchmarks, compared to 3.10.0.
• (Hey, fellow core developer, if a feature you find important is missing from this list, let Pablo know.)

The next pre-release of Python 3.11 will be 3.11.0a4, currently scheduled for Monday, 2022-01-03.

More resources

• Online Documentation
• PEP 664, 3.11 Release Schedule
• Report bugs at https://bugs.python.org.
• Help fund Python and its community.

And now for something completely different

Rayleigh scattering, named after the nineteenth-century British physicist Lord Rayleigh is the predominantly elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation. For light frequencies well below the resonance frequency of the scattering particle, the amount of scattering is inversely proportional to the fourth power of the wavelength. Rayleigh scattering results from the electric polarizability of the particles. The oscillating electric field of a light wave acts on the charges within a particle, causing them to move at the same frequency. The particle, therefore, becomes a small radiating dipole whose radiation we see as scattered light. The particles may be individual atoms or molecules; it can occur when light travels through transparent solids and liquids but is most prominently seen in gases.

The strong wavelength dependence of the scattering means that shorter (blue) wavelengths are scattered more strongly than longer (red) wavelengths. This results in the indirect blue light coming from all regions of the sky.