Python not sorting unicode properly. Strcoll doesn't help

user_124090 0
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I've got a problem with sorting lists using unicode collation in Python 2.5.1 and 2.6.5 on OSX, as well as on Linux. 

import locale   
locale.setlocale(locale.LC_ALL, 'pl_PL.UTF-8')
print [i for i in sorted([u'a', u'z', u'ą'], cmp=locale.strcoll)]

Which should print:

[u'a', u'ą', u'z']

But instead prints out:

[u'a', u'z', u'ą']

Summing it up - it looks as if strcoll was broken. Tried it with various types of variables (fe. non-unicode encoded strings).

What do I do wrong?

Best regards, Tomasz Kopczuk.

locale unicode python
7 Answers

Since 2012 there's been a library natsort. It includes amazing functions such as natsorted and humansorted. More importantly, they work not only with lists!. Code:

from natsort import natsorted, humansorted

lst = [u"a", u"z", u"ą"]
dct = {"ą": 1, "ż": 3, "Ż": 4, "b": 5}

lst_natsorted = natsorted(lst)
lst_humansorted = humansorted(lst)
dct_natsorted = dict(natsorted(dct.items()))
dct_humansorted = dict(humansorted(dct.items()))

print("List natsorted: ", lst_natsorted)
print("List humansorted: ", lst_humansorted, "\n")
print("Dictionary natsorted: ", dct_natsorted)
print("Dictionary humansorted: ", dct_humansorted)

Output:

List natsorted:  ['a', 'ą', 'z']
List humansorted:  ['a', 'ą', 'z']

Dictionary natsorted:  {'Ż': 4, 'ą': 1, 'b': 5, 'ż': 3}  
Dictionary humansorted:  {'ą': 1, 'b': 5, 'ż': 3, 'Ż': 4}

As you can see results differ when sorting dictionaries but considering given list both results are correct.

By the way, this library is also great to sort strings containing numbers:

from natsort import natsorted, humansorted

lst_mixed = ["a9", "a10", "a1", "c4", "c40", "c5"]

mixed_sorted = sorted(lst_mixed)
mixed_natsorted = natsorted(lst_mixed)
mixed_humansorted = humansorted(lst_mixed)

Output:

List with mixed strings sorted:  ['a1', 'a10', 'a9', 'c4', 'c40', 'c5']
List with mixed strings natsorted:  ['a1', 'a9', 'a10', 'c4', 'c5', 'c40']
List with mixed strings humansorted:  ['a1', 'a9', 'a10', 'c4', 'c5', 'c40']
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