DSLs in perl and python (Was sobering observation)

[Jussi Piitulainen]

Rustom Mody writes:

> On Friday, March 18, 2016 at 4:17:06 AM UTC+5:30, MRAB wrote:
>> Stick an "x" on the end of the regex: /something/x or s/old/new/x.
>
> Thanks!
>
> Is there somewhere a regexp 'introspection' API/capability available?
>
> ie if the re looks like
> rexp = r"""
> # DSL (instantiation) for describing NYSE symbology
> ^
> (?P<scrip>	     [A-Z]*)     # The base scrip
> (?P<serchar>	     [.+-])?     # Series type char
> (?P<series>	     [A-Z])?     # Series
> (?P<issuedc>	     [#])?       # issued char indicator
> $		     		 # Thats all (there should be!)
> """
>
> I would like to know that the named-groups are
> {scrip, serchar, series, issued}
> without doing match/search etc
>
> That way then the same DSL could be used for quite different regexps
>
> IOW I would like to generalize the code:
>
> g = m.group
> scrip, serchar, series, issuedc = g('scrip'), g('serchar'), g('series'), g('issuedc')
>
> The scrip, serchar, series etc need not be local vars; 
> a dict is fine/preferable

Maybe the .groupindex in the object that you get when you compile the
regex. Found it with dir(pat), help(pat) was not so helpful. Haven't
looked for other documentation.

   >>> pat = re.compile(r'...(?P<foo>xxx)...(?P<bar>yyy)...')
   >>> pat.groups
   2
   >>> pat.groupindex
   {'bar': 2, 'foo': 1}
   >>> pat.pattern
   '...(?P<foo>xxx)...(?P<bar>yyy)...'