Queen johniek Queen johniek - 2 months ago 13
Python Question

Russian symbols in re (Python)

I get a data from a file:

words = re.findall(r'[\w]+',self._from.encode('utf8'),re.U)


If the file contains:


Hi, how are you?


Then result will be:


['Hi', 'how', 'are', 'you']


But if the file contains russian language (i.e. cyrillic symbols), then:


Привет, как дела?


In this case the result is:


['\xd0', '\xd1', '\xd0', '\xd0\xb2\xd0\xb5\xd1', '\xd0\xba\xd0',
'\xd0\xba', '\xd0', '\xd0\xb5\xd0', '\xd0']


why? wtf?
I've already added:

sys.setdefaultencoding('utf-8')


I'm using python2.7 and linux ubuntu.

Answer:



words = re.findall(r'[\w]+',self._from.decode('utf8'),re.U)
print u" ".join(words)

Answer

To use \w+ to match alphanumeric unicode characters you should pass both a unicode pattern and unicode text to re.findall.

  • In Python2:

    Assuming that you are reading bytes (not text) from the file, you should decode the bytes to obtain a unicode:

    uni = 'Привет, как дела?'.decode('utf-8')
    

    ur'(?u)\w+' is a raw unicode literal. Even though it is not necessary here, using raw unicode/string literals for regex patterns is generally a good practice -- it allows you to avoid the need for double backslashes before certain characters such as \s.

    The regex pattern ur'(?u)\w+' bakes-in the Unicode flag which tells re.findall to make \w dependent on the Unicode character properties database.

    import re
    uni = 'Привет, как дела?'.decode('utf-8')
    print(re.findall(ur'(?u)\w+', uni))
    

    yields a list containing the 3 unicode "words":

    [u'\u041f\u0440\u0438\u0432\u0435\u0442',
     u'\u043a\u0430\u043a',
     u'\u0434\u0435\u043b\u0430']
    
  • In Python3:

    The general principle is the same, except that what were unicodes in Python2 are now strs in Python3, and there is no longer any attempt at automatic conversion between the two. So, again assuming that you are reading bytes (not text) from the file, you should decode the bytes to obtain a str, and use a str regex pattern:

    import re
    uni = b'\xd0\x9f\xd1\x80\xd0\xb8\xd0\xb2\xd0\xb5\xd1\x82, \xd0\xba\xd0\xb0\xd0\xba \xd0\xb4\xd0\xb5\xd0\xbb\xd0\xb0?'.decode('utf')
    print(re.findall(r'(?u)\w+', uni))
    

    yields

    ['Привет', 'как', 'дела']
    
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