0001-python-version-3-6-plus.md

Default to Python 3.6 or newer for new development

• Status: accepted
• Date: 2020-10-20

Technical Story: theupdateframework#1125

Context and Problem Statement

We are planning a refactor of tuf where:

• We do not want to try and support end-of-life versions of the language.
• We want to use modern language features, such as typing.
• We want to ease maintainer burden, by reducing the major language versions supported.

Decision Drivers

• Python 2.7 is end-of-life
• Python 3.5 is end-of-life
• Modern Python allows use of desirable features such as type hints
• Supporting end-of-life Python versions adds maintenance overhead

Considered Options

• Support Python 2.7 and 3.5+
• Support Python 2.7 and 3.6+
• Support Python 2.7 and 3.6+ (with polyfill modules)
• Support only Python 3.6+

Decision Outcome

Chosen option: "Support only Python 3.6+", because we want modern features and lower maintainer effort as we work to improve our codebase through the refactor effort.

New modules should target Python 3.6+.

Using modules to polyfill standard library features from Python 3.6+ feels untenable as more libraries are dropping support for EOL Python releases.

Negative Consequences

• Leaves major adopter and contributor without an actively developed client for some of their customers stuck on older Python versions.

Links

• Discussion of how/where to develop the refactored codebase
• Discussion of deprecation policy for the pre-1.0, Python 2.7 supporting, code