python – How to sort a list of strings?

python – How to sort a list of strings?

Basic answer:

mylist = [b, C, A]

This modifies your original list (i.e. sorts in-place). To get a sorted copy of the list, without changing the original, use the sorted() function:

for x in sorted(mylist):
    print x

However, the examples above are a bit naive, because they dont take locale into account, and perform a case-sensitive sorting. You can take advantage of the optional parameter key to specify custom sorting order (the alternative, using cmp, is a deprecated solution, as it has to be evaluated multiple times – key is only computed once per element).

So, to sort according to the current locale, taking language-specific rules into account (cmp_to_key is a helper function from functools):

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

And finally, if you need, you can specify a custom locale for sorting:

import locale
locale.setlocale(locale.LC_ALL, en_US.UTF-8) # vary depending on your lang/locale
assert sorted((uAb, uad, uaa),
  key=cmp_to_key(locale.strcoll)) == [uaa, uAb, uad]

Last note: you will see examples of case-insensitive sorting which use the lower() method – those are incorrect, because they work only for the ASCII subset of characters. Those two are wrong for any non-English data:

# this is incorrect!
mylist.sort(key=lambda x: x.lower())
# alternative notation, a bit faster, but still wrong

It is also worth noting the sorted() function:

for x in sorted(list):
    print x

This returns a new, sorted version of a list without changing the original list.

python – How to sort a list of strings?


It really is that simple 🙂

Leave a Reply

Your email address will not be published. Required fields are marked *