exec'ing functions (WAS: updating locals() and globals())
Steven Bethard
steven.bethard at gmail.com
Wed Dec 8 22:44:02 EST 2004
Jeff Shannon wrote:
> Steven Bethard wrote:
>
>> Jeff Shannon wrote:
>>
>>> Note also that functions which use exec cannot use the static
>>> namespace optimization, and thus tend to be *much* slower than normal
>>> functions
>>
>> In what circumstances will this be true? I couldn't verify it:
[snip]
>
> I was referring to functions which have an internal exec statement, not
> functions which are created entirely within an exec -- i.e., something
> like this:
Thanks for the clarification. Here's the results for some functions
with internal exec statements:
> cat fib.py
def fib1(n):
a, b = 0, 1
while True:
a, b = b, a + b
yield a
exec """\
def fib2(n):
a, b = 0, 1
while True:
a, b = b, a + b
yield a
"""
def fib3(n):
a, b = 0, 1
while True:
exec "a, b = b, a + b"
yield a
def fib4(n):
exec "a, b = 0, 1"
while True:
exec "a, b = b, a + b"
yield a
>
> python -m timeit -s "import fib" "fib.fib1(100)"
1000000 loops, best of 3: 0.71 usec per loop
> python -m timeit -s "import fib" "fib.fib2(100)"
1000000 loops, best of 3: 0.678 usec per loop
> python -m timeit -s "import fib" "fib.fib3(100)"
1000000 loops, best of 3: 0.826 usec per loop
> python -m timeit -s "import fib" "fib.fib4(100)"
1000000 loops, best of 3: 0.821 usec per loop
I'm not sure I'd say they're *much* slower, but you're right; they're
definitely slower.
Steve
More information about the Python-list
mailing list