Sorting techniques edits

[rhettinger]

• Mention other ordering tools that use key-functions (min, max, nsmallest, nlargest).
• Add a documentation link to str.casefold in case it is unknown to readers.
• Add tips for handling inputs that aren't directly sortable.

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📚 Documentation preview 📚: https://cpython-previews--124701.org.readthedocs.build/

[JelleZijlstra]

Why not use key= here?

Suggested change

	>>> list(map(dict, sorted(map(methodcaller('items'), data))))
	>>> sorted(data, key=methodcaller('items'))

[rhettinger]

I don't think this works. IIRC, an items-view implements set-like comparisons which are a subset/superset tests instead of a total ordering. Also, the intent here was to sort the key/value pairs to so that dicts that compare equal regardless of key ordering will appear side-by-side in the output.

[JelleZijlstra]

It does work here, but it does rely on the set operations and will not work for all dicts. However, that is also true for your version:

>>> data = [{'a': 1}, {'b': 2}, {'a': 3}]
>>> list(map(dict, sorted(map(methodcaller('items'), data))))
[{'a': 1}, {'b': 2}, {'a': 3}]
>>> sorted(data, key=methodcaller('items'))
[{'a': 1}, {'b': 2}, {'a': 3}]

To work correctly, we need to sort the itemsviews:

>>> sorted(data, key=lambda d: sorted(d.items()))
[{'a': 1}, {'a': 3}, {'b': 2}]

[rhettinger]

That makes sense.