DC3: Supported Python versions
|Proposal||Supported Python versions|
DIALS supports a number of recent Python versions. However, supporting too old versions of Python does limit us both in terms of available language features and upstream dependency support. To resolve this conflict DIALS will follow the NEP-29 deprecation calendar, which has been widely adopted by the Scientific Python community.
According to this schedule, DIALS will support a Python release for approximately 42 months after its release. With a Python release cadence of 12 months this means DIALS will support the 3-4 most recent Python releases at any point in time.
NEP-29 includes a support table and drop schedule for upcoming versions of Python and Numpy.
DIALS will deviate from NEP-29 in that deprecations will take effect following the next release after deprecation.
If, for example, on the deprecation day of Python 3.A the current release version of DIALS is 3.N, then Python 3.A support will be dropped from the main development branch once the release branch for DIALS 3.N+1 has been made. DIALS 3.N+1.0 will therefore support Python 3.A, and future DIALS releases such as 3.N+2.0 will not.
We will not deprecate Python version support within a DIALS release. So, if DIALS 3.N+1.0 supports Python 3.A, then all patch releases (3.N+1.1, 3.N+1.2, …) will retain Python 3.A support.
DIALS releases generally are supported until the next release is published. This support may be extended in the case of releases that are the final release supporting a particular version of Python. Extended support can take the form of point releases including binary builds, point releases without binary builds, or just accepting source tree changes without release tags. No support will be provided outside of release branches, or where the Python version in question is itself no longer supported.