On 10Jul2014 01:57, rxjw...@gmail.com <rxjw...@gmail.com> wrote:
It says that: match checks for a match only at the beginning of the string.
Then, it also says that: \1...\9 Matches nth grouped subexpression.
I don't know how to write a script to include grouped subexpression in match?
A grouped subexpression is just a portion of a regexp marked out. They serve
two main purposes: to refer to a portion of the expression as you intend, and
to mark a section of the regexp for use by a modifier.
Here's an example:
Suppose you're reading a file and trying to match lines like:
Hours logged: 12
You might use a regexp like this:
Hours logged: (\d+)
If you match with the expression above, the "\d+" portion will match one or
more digits i.e. the "12" in the example line earlier. The "(\d+)" is a grouped
subexpression, the first one (and only one).
If you write a little test script (untested):
import re
TESTLINE = "Hours logged: 12"
regexp = re.compile( r'Hours logged: (\d+)' )
m = regexp.match(TESTLINE)
print "subgroup 1:", m.group(1)
that should print "12".
Cheers,
Cameron Simpson <c...@zip.com.au>
Ignorance is preferable to error; and he is less remote from the truth
who believes nothing, than he who believes what is wrong.
- Thomas Jefferson
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