On 2020-04-08 17:53, Guido van Rossum wrote:
Look at the following code.
def foo(a, b):
x = a + b
if not x:
return None
sleep(1) # A calculation that does not use x
return a*b
This code DECREFs x when the frame is exited (at the return statement).
But (assuming) we can clearly see that x is not needed during the sleep
(representing a big calculation), we could insert a "del x" statement
before the sleep.
I think our compiler is smart enough to find out *some* cases where it
could safely insert such del instructions. And this would potentially
save some memory. (For example, in the above example, if a and b are
large lists, x would be an even larger list, and its memory could be
freed earlier.)
For sure, we could manually insert del statements in code where it
matters to us. But if the compiler could do it in all code, regardless
of whether it matters to us or not, it would probably catch some useful
places where we wouldn't even have thought of this idea, and we might
see a modest memory saving for most programs.
Can anyone tear this idea apart?
Can you be sure that 'sleep' isn't inspecting the stack and using x?
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