On 11 July 2017 at 18:22, Rocky Bernstein <r...@dustyfeet.com> wrote:
> There's too much generalization and abstraction in the discussion at least
> for me. So let me try to make this a little more concrete with real
> examples. First note that, although Python, yes, does "optimize" "if 0:"
> away, as soon as
> you do something as simple as "debug = 0; if debug:" it is confounded. And
> in my own experience I have done this.
>
Typically DEBUG is a global in the module, which means it can be set
from /outside/ the module, so it's not constant as far as the runtime
is concerned. Within a function it's a bit wacky sure, and is only
kept around for interactive debugging reasons afaict.
Here's a possible type for `self.a` which illustrates why
CSE/Store-Sinking on a STORE_ATTR is not valid for the example
function `foo`.
class A(object):
def set_b(self, value):
print value
self._b = value
b = property(set_b)
class Example(object):
def __init__(self):
self.a = A()
def foo(self):
self.a.b = 5
x = 0
if x:
self.a.b = 2
else:
return
Example().foo()
--
William Leslie
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