data regex match

[Gary Wessle]

Hi

I am having an issue with this match

tx = "now 04/30/2006 then"
data = re.compile('(\d {2})/\1/\1\1', re.IGNORECASE)
d = data.search(tx)
print d

Nono
I was expecting 04/30/2006, what went wrong?

thanks

[Fredrik Lundh]

Re: data regex match

Gary Wessle wrote:
[color=blue]
> I am having an issue with this match
>
> tx = "now 04/30/2006 then"
> data = re.compile('(\d {2})/\1/\1\1', re.IGNORECASE)
> d = data.search(tx)
> print d
>
> Nono
> I was expecting 04/30/2006[/color]

really? your pattern matches two digits, followed by a slash, followed
by a byte with the ASCII value 1, followed by a slash, followed by two
bytes with the ASCII value 1.
[color=blue][color=green][color=darkred]
>>> '(\d{2})/\1/\1\1'[/color][/color][/color]
'(\\d{2})/\x01/\x01\x01'

in case you meant to write

r'(\d{2})/\1/\1\1'

(which is the same thing as '(\\d{2})/\\1/\\1\\1')

it's still not close; that pattern matches two digits, followed by a slash,
followed by the *same* two digits, followed by a slash, followed by the
same two digits, followed by the same two digits.

in other words, dates like 20/20/2020 and 12/12/1212.

try

'\d\d/\d\d/\d\d\d\d'

instead.
[color=blue]
> what went wrong?[/color]

(insert obligatory jwz quote here)

</F>

[Heiko Wundram]

Re: data regex match

Am Dienstag 02 Mai 2006 23:06 schrieb Gary Wessle:[color=blue]
> Hi
>
> I am having an issue with this match
>
> tx = "now 04/30/2006 then"
> data = re.compile('(\d {2})/\1/\1\1', re.IGNORECASE)[/color]

As always, use a raw string for regular expressions. \d is being interpreted
to mean an ascii character, and not to mean the character class you're trying
to reference here.

Second: \1 (if properly quoted in the string) matches the first group exactly.
Your regex would only match 20/20/2020 or strings of such format.

Third: IGNORECASE is irrelevant here, you're not trying to match letters, are
you?

Anyway, the following works:

dateregex = re.compile(r"(\ d{2})/(\d{2})/(\d{4})")
m = dateregex.searc h(tx)
if m:
print m.groups()
else:
print "No match."

--- Heiko.

[Rene Pijlman]

Re: data regex match

Gary Wessle:[color=blue]
>tx = "now 04/30/2006 then"
>data = re.compile('(\d {2})/\1/\1\1', re.IGNORECASE)
>d = data.search(tx)
>print d
>
>Nono
>I was expecting 04/30/2006[/color]

You should expect: NameError: name 're' is not defined
[color=blue]
> what went wrong?[/color]

\1 matches the content of the first group, which is '04'. It doesn't match
'30', '20' and '06'.

Also, you'll need to use a raw string, or backslash your backslashes.
[color=blue][color=green][color=darkred]
>>> import re
>>> tx = "now 04/04/0404 then"
>>> data = re.compile(r'(\ d{2})/\1/\1\1', re.IGNORECASE)
>>> d = data.search(tx)
>>> print d[/color][/color][/color]
<_sre.SRE_Mat ch object at 0x01287F60>

--
René Pijlman

[Heiko Wundram]

Re: data regex match

Am Dienstag 02 Mai 2006 23:23 schrieb Fredrik Lundh:[color=blue]
> Gary Wessle wrote:[color=green]
> > regular expression match: what went wrong?[/color]
> (insert obligatory jwz quote here)[/color]

QOTW! :-D

--- Heiko.

[Fredrik Lundh]

Re: data regex match

Heiko Wundram wrote:
[color=blue]
> As always, use a raw string for regular expressions. \d is being interpreted
> to mean an ascii character, and not to mean the character class you're trying
> to reference here.[/color]

\d isn't an ASCII character, but \1 is.
[color=blue][color=green][color=darkred]
>>> print '(\d{2})/\1/\1\1'[/color][/color][/color]
(\d{2})/?/??

</F>

[Heiko Wundram]

Re: data regex match

Am Dienstag 02 Mai 2006 23:34 schrieb Fredrik Lundh:[color=blue]
> Heiko Wundram wrote:[color=green]
> > As always, use a raw string for regular expressions. \d is being
> > interpreted to mean an ascii character, and not to mean the character
> > class you're trying to reference here.[/color]
>
> \d isn't an ASCII character, but \1 is.
>[color=green][color=darkred]
> >>> print '(\d{2})/\1/\1\1'[/color][/color][/color]

I tried that just know. Didn't know that \[a-z] weren't all interpreted as
escape sequences... Seems like I learn something every day. ;-)

--- Heiko.