On Apr 3, 9:56 pm, Jon Clements <jon...@googlemail.com> wrote:
> On 4 Apr, 02:14, bwgoudey <bwgou...@gmail.com> wrote:
>
>
>
> > I have a lot of if/elif cases based on regular expressions that I'm using to
> > filter stdin and using print to stdout. Often I want to print something
> > matched within the regular expression and the moment I've got a lot of cases
> > like:
>
> > ...
> > elif re.match("^DATASET:\s*(.+) ", line):
> > m=re.match("^DATASET:\s*(.+) ", line)
> > print m.group(1))
>
> > which is ugly because of the duplication but I can't think of a nicer of way
> > of doing this that will allow for a lot of these sorts of cases. Any
> > suggestions?
> > --
> > View this message in
> > context:http://www.nabble.com/Best-way-to-extract-from-regex-in-if-statement-...
> > Sent from the Python - python-list mailing list archive at Nabble.com.
>
> How about something like:
>
> your_regexes = [
> re.compile('rx1'),
> re.compile('rx2'),
> # etc....
> ]
>
> for line in lines:
> for rx in your_regexes:
> m = rx.match(line)
> if m:
> print m.group(1)
> break # if only the first matching regex is required,
> otherwise leave black for all
>
> Untested, but seems to make sense
Or in case you want to handle each regexp differently, you can
construct a dict {regexp : callback_function} that picks the right
action depending on which regexp matched. As for how to populate the
dict, if most methods are short expressions, lambda comes in pretty
handly, e.g.
{
rx1: lambda match: match.group(1),
rx2: lambda match: sum(map(int, match.groups())),
...
}
If not, you can combine the handler definition with the mapping update
by using a simple decorator factory such as the following (untested):
def rxhandler(rx, mapping):
rx = re.compile(rx)
def deco(func):
mapping[rx] = func
return func
return deco
d = {}
@rxhandler("^DATASET:\s*(.+) ", d)
def handle_dataset(match):
...
@rxhandler("^AUTHORS:\s*(.+) ", d)
def handle_authors(match):
...
HTH,
George
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