regexp qns

[eight02645999@yahoo.com]

hi
suppose i have a string like

test1?test2t-test3*test4*tes t5$test6#test7* test8

how can i construct the regexp to get test3*test4*tes t5 and
test7*test8, ie, i want to match * and the words before and after?
thanks

[James Stroud]

Re: regexp qns

eight02645999@y ahoo.com wrote:

hi
suppose i have a string like
>
test1?test2t-test3*test4*tes t5$test6#test7* test8
>
how can i construct the regexp to get test3*test4*tes t5 and
test7*test8, ie, i want to match * and the words before and after?
thanks
>

pyimport re
pys = 'test1?test2t-test3*test4*tes t5$test6#test7* test8'
pyr = re.compile(r'(t est\d(?:\*test\ d)+)')
pyr.findall(s)
['test3*test4*te st5', 'test7*test8']

James

[eight02645999@yahoo.com]

Re: regexp qns

James Stroud wrote:

eight02645999@y ahoo.com wrote:

hi
suppose i have a string like

test1?test2t-test3*test4*tes t5$test6#test7* test8

how can i construct the regexp to get test3*test4*tes t5 and
test7*test8, ie, i want to match * and the words before and after?
thanks

>
>
pyimport re
pys = 'test1?test2t-test3*test4*tes t5$test6#test7* test8'
pyr = re.compile(r'(t est\d(?:\*test\ d)+)')
pyr.findall(s)
['test3*test4*te st5', 'test7*test8']
>
James

thanks !
I check the regexp doc it says:
"""
(?:...)
A non-grouping version of regular parentheses. Matches whatever
regular expression is inside the parentheses, but the substring matched
by the group cannot be retrieved after performing a match or referenced
later in the pattern.
"""
but i could not understand this : r'(test\d(?:\*t est\d)+)'. which
parenthesis is it referring to? Sorry, could you explain the solution ?
thanks

[Gabriel Genellina]

Re: regexp qns


<eight02645999@ yahoo.comescrib ió en el mensaje
news:1169268024 .164643.71320@l 53g2000cwa.goog legroups.com...

hi
suppose i have a string like
>
test1?test2t-test3*test4*tes t5$test6#test7* test8
>
how can i construct the regexp to get test3*test4*tes t5 and
test7*test8, ie, i want to match * and the words before and after?
thanks

I suppose this is just an example and you mean "any word" instead of test1,
test2, etc.
So your pattern would be: word*word*word* word, that is, word* repeated many
times, followed by another word.
To match a word we'll use "\w+", to match an * we have to use "\*" (it's a
special character)
So the regexp would be: "(\w+\*)+\w +"
Since we are not interested in the () as a group by itself -it was just to
describe the repeating pattern- we change it into a non-grouping
parenthesis.
Final version: "(?:\w+\*)+ \w+"

import re
rexp = re.compile(r"(? :\w+\*)+\w+")
lines = [
'test1?test2t-test3*test4*tes t5$test6#test7* test8',
'test1?test2t-test3*test4$tes t6#test7_test8' ,
'test1?nada-que-ver$esto.no.mat chea',
'test1?test2t-test3*test4*',
'test1?test2t-test3*test4',
'test1?test2t-test3*',
]

for line in lines:
print line
for txt in rexp.findall(li ne):
print '->', txt

Test it with some corner cases and see if it does what you expect: no "*",
starting with "*", ending with "*", embedded whitespace before and after the
"*", whitespace inside a word, the very definition of "word"...

--
Gabriel Genellina

[James Stroud]

Re: regexp qns

eight02645999@y ahoo.com wrote:

James Stroud wrote:
>

>>eight02645999 @yahoo.com wrote:
>>

>>>hi
>>>suppose i have a string like
>>>
>>>test1?test 2t-test3*test4*tes t5$test6#test7* test8
>>>
>>>how can i construct the regexp to get test3*test4*tes t5 and
>>>test7*test 8, ie, i want to match * and the words before and after?
>>>thanks
>>>

>>
>>
>>pyimport re
>>pys = 'test1?test2t-test3*test4*tes t5$test6#test7* test8'
>>pyr = re.compile(r'(t est\d(?:\*test\ d)+)')
>>pyr.findall(s )
>>['test3*test4*te st5', 'test7*test8']
>>
>>James

>
>
thanks !
I check the regexp doc it says:
"""
(?:...)
A non-grouping version of regular parentheses. Matches whatever
regular expression is inside the parentheses, but the substring matched
by the group cannot be retrieved after performing a match or referenced
later in the pattern.
"""
but i could not understand this : r'(test\d(?:\*t est\d)+)'. which
parenthesis is it referring to? Sorry, could you explain the solution ?
thanks
>

The outer parentheses are the grouping operator. These are saved and
accessible from a match object via group() or groups() methods. The "\d"
part matches a single digit 0-1. The (?:....) construct is used to make
a non-grouping operator that is not itself remembered for access through
the group() or groups() methods. The expression can also reference
earlier groups, but not groups specified with the non-grouping operator.

You may want to note that this is the most specific regular expression
that would match your given example.

James