There are also peephole optimization. Removing it may prevent false positives for coverage tool http://bugs.python.org/issue2506
On Sat, Sep 10, 2016 at 4:01 AM Steven D'Aprano email@example.com wrote:
On Sat, Sep 10, 2016 at 10:04:46AM +1000, Damien George wrote:
I guess my main question to this list is: if CPython were to add a function to change the optimisation level at runtime, what would it look like?
I don't think it would look like sys.optimize(flag). At the very least, it would have to take *at least* three values:
- no optimizations (the default)
- remove asserts (-O)
- remove asserts and docstrings (-OO)
but even that is very limiting. Why can't I keep asserts, which may be useful and important in running code, but remove docstrings, which mostly are used interactively? I think the idea of "optimization levels" has reached its use-by date and we should start considering separate flags for each individual optimization.
In particular, I expect that some time soon somebody will propose at least one more optimization:
- remove annotations
and I seem to recall somebody requesting the ability to turn off constant folding, although I don't remember why. I can easily imagine Python implementations offering flags to control more complex/risky optimizations:
- resolve built-in names at compile-time
- inline small functions
- unroll loops
etc. Victor Stinner is (I think) working on bringing some of these to CPython, and it seems to me that if they are to be under any user-control at all, a simple optimization level counter is not going to be sufficient. We're going to need a set of flags.
But it seems to me that the ability to change optimizations at runtime would be rather confusing. Shouldn't optimizations, or at least some of them, apply on a per-module basis rather than globally?
I don't even know how to reason about code optimizations if any function I run might have changed the optimization level without my knowledge. So I think this is a very dubious idea.
 Yes, I know that will change the semantics of Python code.
-- Steve _______________________________________________ Python-ideas mailing list Pythonfirstname.lastname@example.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/