regex searching hangs

[Jan Erik Breimo]

"Fortepianissimo" <fortepianissimo at yahoo.com.tw> wrote in message
news:ef08387c.0402080729.621632ca at posting.google.com...
> Could someone explains why the following code hangs (Python 2.3.3)?
>
> --- CODE STARTS ---
> import re
>
> p=re.compile(r'\S+(?:\.\S+)+\.com')
>
> t='......................................'
> p.search(t)
> --- CODE ENDS ---
>

The search doesn't hang, it just takes a long time to compute - the time it
takes almost doubles for each dot you add to t.
If you replace \S in the expression with [^ \t\n\r\f\v.] (ie. no whitespace
and no dots) you'll get the computation time you expect.