Is it better to use an exception or a return code in Python?

Question

You may know this recommendation from Microsoft about the use of exceptions in .NET:

Performance Considerations

...

Throw exc

Answer 1

I did a simple experiment to compare the performance of raising exceptions with the following code:

from functools import wraps
from time import time
import logging

def timed(foo):
    @wraps(foo)
    def bar(*a, **kw):
        s = time()
        foo(*a, **kw)
        e = time()
        print '%f sec' % (e - s)
    return bar

class SomeException(Exception):
    pass

def somefunc(_raise=False):
    if _raise:
        raise SomeException()
    else:
        return

@timed
def test1(_reps):
    for i in xrange(_reps):
        try:
            somefunc(True)
        except SomeException:
            pass

@timed
def test2(_reps):
    for i in xrange(_reps):
        somefunc(False)

def main():

    test1(1000000)
    test2(1000000)

    pass

if __name__ == '__main__':
    main()

With the following results:

• Raising exceptions: 3.142000 sec
• Using return: 0.383000 sec

Exceptions are about 8 times slower than using return.