[Python-Dev] Performance of pre-creating exceptions?

[Guido van Rossum]

Often people build mental models of performance that have little
bearing on reality. Thanks for measuring!

On 3/2/07, Adam Olsen <rhamph at gmail.com> wrote:
> $ python2.5 -m timeit -r 10 -n 1000000 -s 'class Foo(Exception): pass'
> 'try: raise Foo()' 'except: pass'
> 1000000 loops, best of 10: 2.49 usec per loop
> $ python2.5 -m timeit -r 10 -n 1000000 -s 'class Foo(Exception):' -s '
>  def __init__(self): pass' 'try: raise Foo()' 'except: pass'
> 1000000 loops, best of 10: 3.15 usec per loop
> $ python2.5 -m timeit -r 10 -n 1000000 -s 'e = Exception()' 'try:
> raise e' 'except: pass'
> 1000000 loops, best of 10: 2.03 usec per loop
>
> We can get more than half of the benefit simply by using a default
> __init__ rather than a python one.  If you need custom attributes but
> they're predefined you could subclass the exception and have them as
> class attributes.  Given that, is there really a need to pre-create
> exceptions?
>
> --
> Adam Olsen, aka Rhamphoryncus
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-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)