Optimizing Python Testing and Django Migrations

• Coverage.py regex pragmas
• * Python of Yore*
• * nox-uv*
• * A couple Django items*
• Extras
• Joke

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Brian #1: Coverage.py regex pragmas

• Ned Batchelder

• The regex implementation of how coverage.py recognizes pragmas is pretty amazing.

• It’s extensible through plugins

  • covdefaults adds a bunch of default exclusions, and also platform- and version-specific comment syntaxes.
  • coverage-conditional-plugin gives you a way to create comment syntaxes for entire files, for whether other packages are installed, and so on.

• A change from last year (as part of coverage.py 7.6 allows multiline regexes, which let’s us do things like:

  • Exclude an entire file with \\A(?s:.*# pragma: exclude file.*)\\Z
  • Allow start and stop delimiters with # no cover: start(?s:.*?)# no cover: stop
  • Exclude empty placeholder methods with ^\\s*(((async )?def .*?)?\\)(\\s*->.*?)?:\\s*)?\\.\\.\\.\\s*(#|$)
  • See Ned’s article for explanations of these

Michael #2: Python of Yore

• via Matthias
• Use YORE: ... comments to highlight CPython version dependencies.

  # YORE: EOL 3.8: Replace block with line 4.
  if sys.version_info < (3, 9):
  from astunparse import unparse
  else:
  from ast import unparse
  

Then check when they go out of support:

$ yore check --eol-within '5 months'
./src/griffe/agents/nodes/_values.py:11: Python 3.8 will reach its End of Life within approx. 4 months

Even fix them with fix .

Michael #3: nox-uv

• via John Hagen
• What nox-uv does is make it very simple to install uv extras and/or dependency groups into a nox session's virtual environment.
• The versions installed are constrained by uv's lockfile meaning that everything is deterministic and pinned.
• Dependency groups make it very easy to install only want is necessary for a session (e.g., only linting dependencies like Ruff, or main dependencies + mypy for type checking).

Brian #4: A couple Django items

• Stop Using Django's squashmigrations: There's a Better Way
  • Johnny Metz
  • Resetting migrations is sometimes the right thing.
  • Overly simplified summary: delete migrations and start over
• dj-lite
  • Adam Hill
  • Use SQLite in production with Django
  • “Simplify deploying and maintaining production Django websites by using SQLite in production. dj-lite helps enable the best performance for SQLite for small to medium-sized projects. It requires Django 5.1+.”

Extras

Brian:

• Test & Code 237 with Sebastian Ramirez on FastAPI Cloud
• pythontest.com: pytest fixtures nuts and bolts - revisited

Michael:

• New course: Just Enough Python for Data Scientists
• My live stream about uv is now on YouTube
• Cursor CLI: Built to help you ship, right from your terminal.

Joke: Copy/Paste