I have a string from which i want to extract 3 groups:

'19 janvier 2012' -> '19', 'janvier', '2012'

Month name could contain non ASCII characters, so [A-Za-z] does not work for me:

>>> import re
>>> re.search(ur'(\d{,2}) ([A-Za-z]+) (\d{4})', u'20 janvier 2012', re.UNICODE).groups()
(u'20', u'janvier', u'2012')
>>> re.search(ur'(\d{,2}) ([A-Za-z]+) (\d{4})', u'20 février 2012', re.UNICODE).groups()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'groups'
>>> 

I could use \w but it matches digits and underscore:

>>> re.search(ur'(\w+)', u'février', re.UNICODE).groups()
(u'f\xe9vrier',)
>>> re.search(ur'(\w+)', u'fé_q23vrier', re.UNICODE).groups()
(u'f\xe9_q23vrier',)
>>> 

I tried to use [:alpha:], but it’s not working:

>>> re.search(ur'[:alpha:]+', u'février', re.UNICODE).groups()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'groups'
>>> 

If i could somehow match \w without [_0-9], but i don’t know how. And even if i find out how to do this, is there a ready shortcut like [:alpha:] which works in Python?

You can construct a new character class:

[^\W\d_]

instead of \w. Translated into English, it means “Any character that is not a non-alphanumeric character ([^\W] is the same as \w), but that is also not a digit and not an underscore”.

Therefore, it will only allow Unicode letters (if you use the re.UNICODE compile option).