best way to do a series of regexp checks with groups

[Alex Martelli]

Steven Bethard <steven.bethard at gmail.com> wrote:

> I get a bit uneasy from the repeated calls to m.group...  If I was going
> to build a class around the re, I think I might lean towards something like:
> 
> class ReWithMemory(object):
>      def search(self, are, aline):
>          self.mo = re.search(are, aline)
>          return self.mo
>      def groups(self, *indices):
>          return [self.mo.group(i) for i in indices]
> 
> m = ReWithMemory()
> 
> if m.search(r'add (\d+) (\d+)', line):
>      do_add(*m.groups(1, 2))
> elif m.search(r'mult (\d+) (\d+)', line):
>      do_mult(*m.groups(1, 2))
> elif m.search(r'help (\w+)', line):
>      show_help(*m.groups(1))
> 
> Of course, this is even less general-purpose than yours...

I'm not sure what advantage it's supposed to give.  Would you have any
problems writing, say, somecall(X[1], X[2]) ...?  Python normally relies
on indexing one thing at a time, and I see calling m.group(1) etc as
just the same kind of approach.

 
> (And if I saw myself using this much regex code, I'd probably reconsider
> my strategy anyway.) ;)

Surely joining all the regexp's into one big one with | would be faster
and more compact, but, with variable numbers of groups per sub-regexp,
determining which regexp matched can perhaps be tricky (issues with
matching mo.lastindex to the correct sub-regexp).  So, I can understand
the desire to do it sequentially, regexp by regexp.


Alex