Re: exec'ing functions (WAS: updating locals() and globals())

[Steven Bethard]

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
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