Now that MRAB has shown me the follies of my ways I would
like to learn how to properly write the regular expression I
need.
This part:
> rx_works = '\$<[^<:]+?::.*?::\d*?>\$|\$<[^<:]+?::.*?::\d+-\d+>\$'
> # it fails if switched around:
> rx_fails = '\$<[^<:]+?::.*?::\d+-\d+>\$|\$<[^<:]+?::.*?::\d*?>\$'
suggests that I already have a solution. However, in reality this line:
> line = 'junk $<match_A::options A::4>$ junk $<match_B::options B::4-5>$
> junk'
can be either way round (match_A, then match_B or the vice
versa) which, in turn, will switch the rx_works/rx_fails.
Let my try to explain the expression I am actually after
(assuming .compile with re.VERBOSE):
rx_works = '
\$< # start of match is literal '$<'
anywhere inside string
[^<:]+?:: # followed by at least one "character", except
'<' or ':', until the next '::' (this is the placeholder "name")
.*?:: # followed by any number of any "character",
until the next '::' (this is the
placeholder "options")
\d*? # followed by any number of digits
(the max length of placeholder output)
>\$ # followed by '>$'
| # -- OR (in *either* order) --
\$< # start of match is literal '$<'
anywhere inside string
[^<:]+?:: # followed by at least one "character", except
'<' or ':', until the next '::' (this is the placeholder "name")
.*?:: # followed by any number of any "character",
until the next '::' (this is the
placeholder "options")
# now the difference:
\d+-\d+ # followed by one-or-many digits, a '-', and
one-or-many digits (this is the *range*
from with placeholder output)
>\$' # followed by '>$'
I want this to work for
any number of matches
in any order of max-lenght or output-range
inside one string.
Now, why the [^<:]+? dance ?
Because three levels of placeholders
$<...::...::>$
$<<...::...::>>$
$<<<...::...::>>>$
need to be nestable inside each other ;-)
Anyone able to help ?
This seems beyond my current grasp of regular expressions.
Thanks,
Karsten
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