gh-133722: Add 'color' option to 'difflib.unified_diff'

[dougthor42]

Add a color arg (defaulting to False) to difflib.unified_diff. When True, ANSI color codes are injected to the diff lines so that the printed result looks like git diff --color:

>>> import difflib
>>> args = [['one', 'three'], ['two', 'three'], 'Original', 'Current']
>>> for line in difflib.unified_diff(*args, lineterm='', color=True):
...     print(line)
...     
--- Original
+++ Current
@@ -1,2 +1,2 @@
-one
+two
 three

Fixes #133722.

It's a bummer, I just missed the feature freeze window for 3.14 (it was yesterday! 😭), but c'est la vie!

• Issue: Add a color: bool arg to difflib.unified_diff #133722

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📚 Documentation preview 📚: https://cpython-previews--133725.org.readthedocs.build/

[tomasr8]

Thanks for the PR!

With the basic theming support in #133347 merged, perhaps we could define a separate difflib theme and use that here?

[hugovk]

Suggested change

	.. versionchanged:: 3.15
	.. versionchanged:: next

[hugovk]

Thanks for the PR! I had a play with something similar but didn't get very far before the 3.14 freeze.

With the basic theming support in #133347 merged, perhaps we could define a separate difflib theme and use that here?

Yes, let's add theming support.

See this docstring for instructions.

For a couple of standalone examples of adding theme support to a module, see 230d658 and 5c5c3e1 from that PR.

[dougthor42]

Ah, TIL! Thanks, I'll take a look at those docs and update accordingly. It'll be a few days a least before I can get to it, so for now I'll revert this back to draft.

[hugovk]

Absolutely no rush for this, we have 12 months until the 3.15 feature freeze. Don't hesitate if you have questions :)