\w in regular expression

[Marcello Pietrobon]

Hello,

I am reading

http://www.amk.ca/python/howto/regex/

But there is an incongruence:
In the paragraph 2.1: Matching Character:

|\w|
Matches any alphanumeric character; this is equivalent to the class
[a-zA-Z0-9_].

|\W|
Matches any non-alphanumeric character; this is equivalent to the
class |[^a-zA-Z0-9_]|.

Which is fine with me and the same as in Perl and congruent with:

|\d|
Matches any decimal digit; this is equivalent to the class [0-9].

|\D|
Matches any non-digit character; this is equivalent to the class
|[^0-9]|.

|
But in the paragraph 5.1: Splitting Strings
I find:
|
[color=blue][color=green][color=darkred]
>>> p = re.compile(r'\W +')
>>> p.split('This is a test, short and sweet, of split().')[/color][/color][/color]
['This', 'is', 'a', 'test', 'short', 'and', 'sweet', 'of', 'split', '']


At first I thought a typo:
But on my Python command line:
Python 2.3 (#46, Jul 29 2003, 18:54:32) [MSC v.1200 32 bit (Intel)] on win32
Type "help", "copyright" , "credits" or "license" for more information.[color=blue][color=green][color=darkred]
>>> import re
>>> p = re.compile(r'\W +'); print p[/color][/color][/color]
<_sre.SRE_Patte rn object at 0x0090DC38>[color=blue][color=green][color=darkred]
>>> p.split('This is a test, short and sweet, of split().')[/color][/color][/color]
['This', 'is', 'a', 'test', 'short', 'and', 'sweet', 'of', 'split', ''][color=blue][color=green][color=darkred]
>>> p = re.compile(r'\w +'); print p[/color][/color][/color]
<_sre.SRE_Patte rn object at 0x0090D140>[color=blue][color=green][color=darkred]
>>> p.split('This is a test, short and sweet, of split().')[/color][/color][/color]
['', ' ', ' ', ' ', ', ', ' ', ' ', ', ', ' ', '().'][color=blue][color=green][color=darkred]
>>>[/color][/color][/color]



In other word is Python re module not compatible with Perl ?


I also noted that the tools\scripts\r edemo.py behaves different than the Python command line ( it is not the only case )
because it matches 'This' when I use \w+ and not when I use \W+


???


Thank you for any comments,

Marcello






||

[William Park]

Re: \w in regular expression

Marcello Pietrobon <teiffel@attglo bal.net> wrote:[color=blue][color=green][color=darkred]
> >>> p = re.compile(r'\W +')
> >>> p.split('This is a test, short and sweet, of split().')[/color][/color]
> ['This', 'is', 'a', 'test', 'short', 'and', 'sweet', 'of', 'split', '']
>
> At first I thought a typo:[/color]

It's correct. No typo.
[color=blue]
> In other word is Python re module not compatible with Perl ?[/color]

What answer were you expecting in Perl?

--
William Park, Open Geometry Consulting, <opengeometry@y ahoo.ca>
Linux solution for data management and processing.

[stewart]

Re: \w in regular expression

Marcello Pietrobon wrote:
[color=blue]
> I also noted that the tools\scripts\r edemo.py behaves different than the
> Python command line ( it is not the only case )
> because it matches 'This' when I use \w+ and not when I use \W+[/color]

This doesn't sound like an error to me. \w+ matches all lowercase and
uppercase letters, and numbers, while \W+ matches everything else. So of
course 'This' will be matched by \w+ and not by \W+. It sounds like your
impression was that \w+ matched only lowercase letters, which is not the
case.