How to write Regular Expression for recursive matching?

[lisong]

Hi All,

I have problem to split a string like this:

'abc.defg.hij.klmnop'

and I want to get all substrings with only one '.' in mid. so the
output I expect is :

'abc.defg', 'defg.hij', 'hij.klmnop'

a simple regular expression '\w+.\w' will only return:
'abc.defg', 'hij.klmnop'

is there a way to get 'defg.hij' using regular expression?

Thanks,

[Paul McGuire]

On Nov 26, 10:40 am, lisong <[e-mail]:

Hi All,

I have problem to split a string like this:

'abc.defg.hij.klmnop'

and I want to get all substrings with only one '.' in mid. so the
output I expect is :

'abc.defg', 'defg.hij', 'hij.klmnop'

a simple regular expression '\w+.\w' will only return:
'abc.defg', 'hij.klmnop'

is there a way to get 'defg.hij' using regular expression?

Thanks,

Why are you using regular expressions? Use the split method defined
for strings:

>>'abc.defg.hij.klmnop'.split('.')

['abc', 'defg', 'hij', 'klmnop']

-- Paul

[Diez B. Roggisch]

lisong wrote:

Hi All,

I have problem to split a string like this:

'abc.defg.hij.klmnop'

and I want to get all substrings with only one '.' in mid. so the
output I expect is :

'abc.defg', 'defg.hij', 'hij.klmnop'

a simple regular expression '\w+.\w' will only return:
'abc.defg', 'hij.klmnop'

is there a way to get 'defg.hij' using regular expression?

Nope. Regular expressions can't get back in their input-stream, at least not
for such stuff.

The problem at hand is easily solved using

s = 'abc.defg.hij.klmnop'

pairs = [".".join(v) for v in zip(s.split(".")[:-1], s.split(".")[1:])]

Diez

[Paul McGuire]

On Nov 26, 10:51 am, Paul McGuire <[e-mail]:

On Nov 26, 10:40 am, lisong <[e-mail]:

Hi All,

I have problem to split a string like this:

'abc.defg.hij.klmnop'

and I want to get all substrings with only one '.' in mid. so the
output I expect is :

'abc.defg', 'defg.hij', 'hij.klmnop'

a simple regular expression '\w+.\w' will only return:
'abc.defg', 'hij.klmnop'

is there a way to get 'defg.hij' using regular expression?

Thanks,

Why are you using regular expressions? Use the split method defined
for strings:

>'abc.defg.hij.klmnop'.split('.')

['abc', 'defg', 'hij', 'klmnop']

-- Paul- Hide quoted text -

- Show quoted text -

Sorry, misread your post - Diez Roggisch has the right answer.

-- Paul

[Boris Borcic]

lisong wrote:

Hi All,

I have problem to split a string like this:

'abc.defg.hij.klmnop'

and I want to get all substrings with only one '.' in mid. so the
output I expect is :

'abc.defg', 'defg.hij', 'hij.klmnop'

a simple regular expression '\w+.\w' will only return:
'abc.defg', 'hij.klmnop'

is there a way to get 'defg.hij' using regular expression?

Thanks,

Do you need it to be a regular expression ?

>>def f(s) :

ws = s.split('.')
return map('.'.join,zip(ws,ws[1:]))

>>f('abc.defg.hij.klmnop')

['abc.defg', 'defg.hij', 'hij.klmnop']

[J. Clifford Dyer]

On Mon, Nov 26, 2007 at 06:04:54PM +0100, Diez B. Roggisch wrote regarding Re: How to write Regular Expression for recursive matching?:

>
lisong wrote:

Hi All,

I have problem to split a string like this:

'abc.defg.hij.klmnop'

and I want to get all substrings with only one '.' in mid. so the
output I expect is :

'abc.defg', 'defg.hij', 'hij.klmnop'

a simple regular expression '\w+.\w' will only return:
'abc.defg', 'hij.klmnop'

is there a way to get 'defg.hij' using regular expression?

Nope. Regular expressions can't get back in their input-stream, at least not
for such stuff.

The problem at hand is easily solved using

s = 'abc.defg.hij.klmnop'

pairs = [".".join(v) for v in zip(s.split(".")[:-1], s.split(".")[1:])]

which is veritably perlesque in its elegance and simplicity!

A slightly more verbose version.

l = s.split('.')
pairs = []
for x in xrange(len(l)-1):
pairs.append('.'.join(l[x:x+2]))

Cheers,
Cliff

[lisong]

On Nov 26, 12:34 pm, "J. Clifford Dyer" <[e-mail]:

On Mon, Nov 26, 2007 at 06:04:54PM +0100, Diez B. Roggisch wrote regarding Re: How to write Regular Expression for recursive matching?:

lisong wrote:

Hi All,

I have problem to split a string like this:

'abc.defg.hij.klmnop'

and I want to get all substrings with only one '.' in mid. so the
output I expect is :

'abc.defg', 'defg.hij', 'hij.klmnop'

a simple regular expression '\w+.\w' will only return:
'abc.defg', 'hij.klmnop'

is there a way to get 'defg.hij' using regular expression?

Nope. Regular expressions can't get back in their input-stream, at least not
for such stuff.

The problem at hand is easily solved using

s = 'abc.defg.hij.klmnop'

pairs = [".".join(v) for v in zip(s.split(".")[:-1], s.split(".")[1:])]

which is veritably perlesque in its elegance and simplicity!

A slightly more verbose version.

l = s.split('.')
pairs = []
for x in xrange(len(l)-1):
pairs.append('.'.join(l[x:x+2]))

Cheers,
Cliff

Thank u all for your kindly reply, I agree, RE is not necessary here.

Song