How to Sort Strings in Python: In-Place, Copies, Locale-Aware, and Custom Locales?

Sorting Lists of Strings in Python

One of the common tasks in programming is sorting a list of strings. In Python, there are several ways to achieve this, each with its own merits and caveats.

In-Place Sorting

The simplest approach is to use the sort() method directly on the list. This modifies the original list, sorting its elements alphabetically in-place. However, this approach is not ideal if you want to preserve the original order of the list.

mylist = ["b", "C", "A"]
mylist.sort()

Creating Sorted Copies

To obtain a sorted copy of a list without modifying the original, use the sorted() function:

for x in sorted(mylist):
    print(x)

Locale-Aware Sorting

The sorting methods described above perform case-sensitive, non-locale-aware sorting. To account for locale-specific rules, you can use the key parameter of the sort() or sorted() functions, along with the cmp_to_key() helper function from the functools module:

sorted(mylist, key=cmp_to_key(locale.strcoll))

This will sort the list according to the current locale settings.

Custom Locales

Finally, if you need to specify a custom locale for sorting, use the setlocale() function from the locale module:

import locale
locale.setlocale(locale.LC_ALL, 'en_US.UTF-8')
sorted((u'Ab', u'ad', u'aa'), key=cmp_to_key(locale.strcoll))

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