Simple Python REGEX Question
James T. Dennis
jadestar at idiom.com
Sat May 12 17:38:04 EDT 2007
johnny <rampeters at gmail.com> wrote:
> I need to get the content inside the bracket.
> eg. some characters before bracket (3.12345).
> I need to get whatever inside the (), in this case 3.12345.
> How do you do this with python regular expression?
I'm going to presume that you mean something like:
I want to extract floating point numerics from parentheses
embedded in other, arbitrary, text.
Something like:
>>> given='adfasdfafd(3.14159265)asdfasdfadsfasf'
>>> import re
>>> mymatch = re.search(r'\(([0-9.]+)\)', given).groups()[0]
>>> mymatch
'3.14159265'
>>>
Of course, as with any time you're contemplating the use of regular
expressions, there are lots of questions to consider about the exact
requirements here. What if there are more than such pattern? Do you
only want the first match per line (or other string)? (That's all my
example will give you). What if there are no matches? My example
will raise an AttributeError (since the re.search will return the
"None" object rather than a match object; and naturally the None
object has no ".groups()' method.
The following might work better:
>>> mymatches = re.findall(r'\(([0-9.]+)\)', given).groups()[0]
>>> if len(mymatches):
>>> ...
... and, of couse, you might be better with a compiled regexp if
you're going to repeast the search on many strings:
num_extractor = re.compile(r'\(([0-9.]+)\)')
for line in myfile:
for num in num_extractor(line):
pass
# do whatever with all these numbers
--
Jim Dennis,
Starshine: Signed, Sealed, Delivered
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