Regex and unicode

Question

I have a script that parses the filenames of TV episodes (show.name.s01e02.avi for example), grabs the episode name (from the www.thetvdb.com API) and automatically renames them into something nicer (Show Name - [01x02].avi)

The script works fine, that is until you try and use it on files that have Unicode show-names (something I never really thought about, since all the files I have are English, so mostly pretty-much all fall within [a-zA-Z0-9'\-])

How can I allow the regular expressions to match accented characters and the likes? Currently the regex's config section looks like..

config['valid_filename_chars'] = """0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!@£$%^&*()_+=-[]{}"'.,<>`~? """
config['valid_filename_chars_regex'] = re.escape(config['valid_filename_chars'])

config['name_parse'] = [
    # foo_[s01]_[e01]
    re.compile('''^([%s]+?)[ \._\-]\[[Ss]([0-9]+?)\]_\[[Ee]([0-9]+?)\]?[^\\/]*$'''% (config['valid_filename_chars_regex'])),
    # foo.1x09*
    re.compile('''^([%s]+?)[ \._\-]\[?([0-9]+)x([0-9]+)[^\\/]*$''' % (config['valid_filename_chars_regex'])),
    # foo.s01.e01, foo.s01_e01
    re.compile('''^([%s]+?)[ \._\-][Ss]([0-9]+)[\.\- ]?[Ee]([0-9]+)[^\\/]*$''' % (config['valid_filename_chars_regex'])),
    # foo.103*
    re.compile('''^([%s]+)[ \._\-]([0-9]{1})([0-9]{2})[\._ -][^\\/]*$''' % (config['valid_filename_chars_regex'])),
    # foo.0103*
    re.compile('''^([%s]+)[ \._\-]([0-9]{2})([0-9]{2,3})[\._ -][^\\/]*$''' % (config['valid_filename_chars_regex'])),
]

Massif

Answer 1

Use a subrange of [\u0000-\uFFFF] for what you want.

You can also use the re.UNICODE compile flag. The docs say that if UNICODE is set, \w will match the characters [0-9_] plus whatever is classified as alphanumeric in the Unicode character properties database.

See also http://coding.derkeiler.com/Archive/Python/comp.lang.python/2004-05/2560.html.

Cynicism

Answer 2

Python's re module doesn't support \p{Letter} or \X. However, the new regex implementation on PyPI does.

Lotte

That module’s \X is broken; they have misunderstood the standard. You cannot just use \PM\pM* or you get things wrong. Consider the string "\r\r\n\x{301}A\x{301}". A conforming application finds the following 4 matches for \X: 1 CP U+000D, 2 CPs U+000D U+000A, 1 CP U+0301, and 2 CPs U+0041 U+0301. The broken \PM\pM* also finds 4 matches, but the wrong ones: 1 CP U+000D, 1 CP U+000D, 2 CPs U+000A U+0301, and 2 CPs U+0041 U+0301. You MUST not break up CRLFs nor place Marks on any \P{Grapheme_Base} code points. – Antepenult

The definition of \X was based on the contents of this: regular-expressions.info/unicode.html I'll see if I can fix it. – Lotte

The original grapheme cluster idea was a bit confused about a few things, so the first folks to jump on \X ended up doing it a bit wrong. The current ICU and Perl implementations do get it right, and indeed even use the extended grapheme cluster definitions: Try perl5.12.0 -le 'printf "%d %v04X\n", length, $_ for "\r\r\n\x{301}A\x{301}" =~ /\X/g' or later to see the improved answers. – Antepenult

@tchrist: It seems to be fixed now (or never been broken). python -c'import regex as re; print(re.findall(u"\X", u"\r\r\n\u0301A\u0301"))' prints expected results: [u'\r', u'\r\n', u'\u0301', u'A\u0301'] – Maineetloire

@J.F.Sebastian I know it did get fixed. I corresponded with the author at length. He’s great. – Antepenult

Answer 3

In Mastering Regular Expressions from Jeffrey Friedl (great book) it is mentioned that you could use \p{Letter} which will match unicode stuff that is considered a letter.

Civil

\p{Letter} is not supported in all regex engines, and in Python's case, it's not supported in the default re engine. It's only supported in the regex package. – Owen

Answer 4

\X seems to be available as a generic word-character in some languages, it allows you to match a single character disregarding of how many bytes it takes up. Might be useful.

Benedicite