When I use the scanner object in re module, I can create groups on regex and associate this to a method...


In [17]: re.Scanner([(r"(\w)(\w)\w", foo)])
Out[17]: <re.Scanner instance at 0x15c4e60>


But I tryed 3 groups and it raises "invalid SRE code", but I think my regex is not wrong...


In [15]: scan = re.Scanner([(r"(\w)(\w)(\w)", foo)])
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)

/home/angelo/<ipython console> in <module>()

/usr/lib/python2.7/re.pyc in __init__(self, lexicon, flags)
    305         s.groups = len(p)+1
    306         p = sre_parse.SubPattern(s, [(BRANCH, (None, p))])
--> 307         self.scanner = sre_compile.compile(p)
    308     def scan(self, string):
    309         result = []

/usr/lib/python2.7/sre_compile.pyc in compile(p, flags)
    520     return _sre.compile(
    521         pattern, flags | p.pattern.flags, code,
    522         p.pattern.groups-1,
--> 523         groupindex, indexgroup
    524         )

RuntimeError: invalid SRE code

Even if this bug is fixed, it still won't work as you expect, and this s why.

The Scanner function accepts a list of 2-tuples. The first item of the tuple is a regex and the second is a function. For example:

    re.Scanner([(r"\d+", number), (r"\w+", word)])

The Scanner function then builds a regex, using the given regexes as alternatives, each wrapped as a capture group:

    r"(\d+)|(\w+)"

When matching, it sees which group captured and uses that to decide which function it should call, so, for example, if group 1 matched, it calls "number", and if group 2 matched, it calls "word".

When you introduce capture groups into the regexes, it gets confused. If your regex matches, it'll see that groups 1 and 2 match, so it'll try to call the second function, but there's isn't one...

Ah, ok, thanks...
Then I think my idea is impossible.
I will use the Scanner in normal way. :)