Match unicode in ply's regexes

Question

I'm matching identifiers, but now I have a problem: my identifiers are allowed to contain unicode characters. Therefore the old way to do things is not enough:

t_IDENTIFIER = r"[A-Za-z](\\.|[A-Za-z_0-9])*"

In my markup language parser I match unicode characters by allowing all the characters except those I explicitly use, because my markup language only has two or three of characters I need to escape that way.

How do I match all unicode characters with python regexs and ply? Also is this a good idea at all?

I'd want to let people use identifiers like Ω » « ° foo² väli π as an identifiers (variable names and such) in their programs. Heck! I want that people could write programs in their own language if it's practical! Anyway unicode is supported nowadays in wide variety of places, and it should spread.

Edit: POSIX character classes doesnt seem to be recognised by python regexes.

>>> import re
>>> item = re.compile(r'[[:word:]]')
>>> print item.match('e')
None

Edit: To explain better what I need. I'd need a regex -thing that matches all the unicode printable characters but not ASCII characters at all.

Edit: r"\w" does a bit stuff what I want, but it does not match « », and I also need a regex that does not match numbers.

Answer 1

Probably POSIX character classes are right for you?

Answer 2

Check the answers to this question

http://stackoverflow.com/questions/92438/stripping-non-printable-characters-from-a-string-in-python

you'd just need to use the other unicode character categories instead

Answer 3

Solved it with the help of Vinko.

I realised that getting unicode range is plain dumb. So I'll do this:

symbols = re.escape(''.join([chr(i) for i in xrange(33, 127) if not chr(i).isalnum()]))
symnums = re.escape(''.join([chr(i) for i in xrange(33, 127) if not chr(i).isalnum()]))

t_IDENTIFIER = "[^%s](\\.|[^%s])*" % (symnums, symbols)

I don't know about unicode character classses. If this unicode stuff starts getting too complicated, I can just put the original one in place. UTF-8 support still ensures the support is on at the STRING tokens, which is more important.

Edit: On other hand, I start understanding why there's not much unicode support in programming languages.. This is an ugly hack, not a satisfying solution.

Answer 4

the re module supports the \w syntax which:

If UNICODE is set, this will match the characters [0-9_] plus whatever is classified as alphanumeric in the Unicode character properties database.

therefore the following examples shows how to match unicode identifiers:

>>> import re
>>> m = re.compile('(?u)[^\W0-9]\w*')
>>> m.match('a')
<_sre.SRE_Match object at 0xb7d75410>
>>> m.match('9')
>>> m.match('ab')
<_sre.SRE_Match object at 0xb7c258e0>
>>> m.match('a9')
<_sre.SRE_Match object at 0xb7d75410>
>>> m.match('unicöde')
<_sre.SRE_Match object at 0xb7c258e0>
>>> m.match('ödipus')
<_sre.SRE_Match object at 0xb7d75410>

So the expression you look for is: (?u)[^\W0-9]\w*