re module - cannot make expression

[Laszlo Zsolt Nagy]

Hi All!

I would like to match strings not beginning with '/webalizer'. How can I
do this?
The only one negation command is ^ inside [] but it cannot be used here.
I looked
over "re" examples on the net but I could not find an example about how
to match
"not beginning with" type expressions.

Thanks,

Laci 2.0

 

[Steve Holden]

Hi All!

I would like to match strings not beginning with '/webalizer'. How can I
do this?
The only one negation command is ^ inside [] but it cannot be used here.
I looked
over "re" examples on the net but I could not find an example about how
to match
"not beginning with" type expressions.

Thanks,

Laci 2.0

You can do taht with Python re's. Look in the re documentation for
"negative lookahead assertion".

regards
Steve

 

[Steven Bethard]

I would like to match strings not beginning with '/webalizer'. How can I
do this?

Are you sure you need a regular expression? The str.startswith method
is what I would normally use to solve this kind of problem:

py> lst = ['aax', 'abx', 'acx', 'aay', 'aby', 'acy']
py> [s for s in lst if not s.startswith('ab')]
['aax', 'acx', 'aay', 'acy']

If you do need a regular expression, Steve Holden's suggestion about
negative lookahead assertions is the right way to go:

py> s = 'aaxabxacxaayabyacy'
py> re.compile(r'(?!ab).{2}[xy]+').findall(s)
['aax', 'acx', 'aay', 'acy']

Steve