Human sorting improved

I wrote about this long ago (Human sorting), but have continued to tweak the code and needed to add it to a project recently. Here’s the latest:

import re

def human_key(s: str) -> tuple[list[str | int], str]:
    """Turn a string into a sortable value that works how humans expect.

    "z23A" -> (["z", 23, "a"], "z23A")

    The original string is appended as a last value to ensure the
    key is unique enough so that "x1y" and "x001y" can be distinguished.

    """
    def try_int(s: str) -> str | int:
        """If `s` is a number, return an int, else `s` unchanged."""
        try:
            return int(s)
        except ValueError:
            return s

    return ([try_int(c) for c in re.split(r"(\d+)", s.casefold())], s)

def human_sort(strings: list[str]) -> None:
    """Sort a list of strings how humans expect."""
    strings.sort(key=human_key)

The central idea here is to turn a string like "Python 3.9" into the key ["Python ", 3, ".", 9] so that numeric components will be sorted by their numeric value. The re.split() function gives us interleaved words and numbers, and try_int() turns the numbers into actual numbers, giving us sortable key lists.

»Ned Batchelder →