Message384956
Can we translate 'if x: pass' into 'pass'? No, because calling its __bool__ method may have a side effect (as we saw at the start of this thread).
Can we eliminate a lone 'x'? Only if it's a local variable and we're *sure* (because of control flow analysis) that it's got a value. For globals and class variables we must execute the load because there could always be an exception (or the dict could have a trap for lookups).
Can we eliminate e.g. 'x.y'? Never, because it can have a side effect.
In general, eliminating this kind of thing seems silly -- in code that the user intends to be fast such things don't occur, and in test the user probably has a reason to write odd code.
On the other question, I don't see how there's any possible difference in evaluation and side effects between
if a and b: ...
and
if a:
if b:
...
so I have no problem with that (in fact that is what it *means*). |
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Args |
2021-01-12 15:47:39 | gvanrossum | set | recipients:
+ gvanrossum, gregory.p.smith, Mark.Shannon, serhiy.storchaka, Mohamed_Atef, pablogsal, stestagg |
2021-01-12 15:47:39 | gvanrossum | set | messageid: <1610466459.51.0.135663607558.issue42899@roundup.psfhosted.org> |
2021-01-12 15:47:39 | gvanrossum | link | issue42899 messages |
2021-01-12 15:47:39 | gvanrossum | create | |
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