My problem is about parsing log files and removing variable parts on each lines to be able to group them. For instance:

s = re.sub(r'(?i)User [_0-9A-z]+ is ', r"User .. is ", s)
s = re.sub(r'(?i)Message rejected because : (.*?) \(.+\)', r'Message rejected because : \1 (...)', s)

I have about 120+ matching rules like those above.

I have found no performances issues while searching successively on 100 different regex. But a huge slow down comes when applying 101 regex.

Exact same behavior happens when replacing my rules set by

for a in range(100):
    s = re.sub(r'(?i)caught here'+str(a)+':.+', r'( ... )', s)

Got 20 times slower when putting range(101) instead.

# range(100)
% ./dashlog.py file.bz2
== Took  2.1 seconds.  ==

# range(101)
% ./dashlog.py file.bz2
== Took  47.6 seconds.  ==

Why such thing is happening ? And is there any known workaround ?

(Happens on Python 2.6.6/2.7.2 on Linux/Windows.)