benchmark

from time import clock as now

def catastrophic(n):
    pat = re.compile('([a|b]+)+c')
    text = "%s" %('a' * n)
    pat.search(text)

def test(f, *args, **kargs):
    start = now()
    f(*args, **kargs)
    print "The function %s lasted: %f" %(f.__name__, now() - start)

for n in range(20, 30):
  test(catastrophic, n)
  
Output:

Testing with 20 characters

The function catastrophic lasted: 0.130457

Testing with 21 characters

The function catastrophic lasted: 0.245125

……

The function catastrophic lasted: 14.828221

Testing with 28 characters

The function catastrophic lasted: 29.830929

Testing with 29 characters

The function catastrophic lasted: 61.110949