Regular expression for not-group

[Chris Lasher]

Is it possible to write a regular expression such that a "match" is
found provided the string does not match a group in the regex? Let me
give a concrete example.

Suppose I want to find a match to any filename that does not end in
..py, (ignoring the obvious use of the .endswith('.py') string method).
I tried the things that were obvious to me, none of which worked.

\.^(py)
\.(^py)
\.[^p][^y]

The last one deceived me at first because it will match "spam.spam",
but not "spam.parrot". I'm a bit stumped at this point. If this can be
done with a regular expression, I'd love to know how, and even if it
can't be, that would be very helpful to know, too.

Many thanks in advance,
Chris

 

[Paddy]

Is it possible to write a regular expression such that a "match" is
found provided the string does not match a group in the regex? Let me
give a concrete example.

Suppose I want to find a match to any filename that does not end in
.py, (ignoring the obvious use of the .endswith('.py') string method).
I tried the things that were obvious to me, none of which worked.

\.^(py)
\.(^py)
\.[^p][^y]

The last one deceived me at first because it will match "spam.spam",
but not "spam.parrot". I'm a bit stumped at this point. If this can be
done with a regular expression, I'd love to know how, and even if it
can't be, that would be very helpful to know, too.

The re module documentation has this snippet:

(?!...)
Matches if ... doesn't match next. This is a negative lookahead
assertion. For example, Isaac (?!Asimov) will match 'Isaac ' only if
it's not followed by 'Asimov'.

- Paddy.

 

[Paddy]

P.S. kodos might help you: http://kodos.sourceforge.net/

- Pad.

 

[Chris Lasher]

Man, that's a headslap-worthy overlooking of the obvious. Ha! =-)

I was using the redemo.py that comes standard with Python but that
Kodos app looks even neater! Thanks for the tip. Thanks Paddy.

Chris