Chris Barker schrieb am 23.02.2018 um 20:23: > BTW, would it be even a tiny bit more efficient to use a tuple in the inner > loop? > > [g(y) for x in range(5) for y in (f(x),)]
Serhiy's optimisation does not use a loop at all anymore and folds it into a direct assignment "y=f(x)" instead. But in general, yes, changing a list iterable into a tuple is an improvement as tuples are more efficient to allocate. Haven't tried it in CPython (*), but it might make a slight difference for very short iterables, which are probably common. Although the execution of the loop body will likely dominate the initial allocation by far. Stefan (*) I implemented this list->tuple transformation in Cython a while ago, but seeing Serhiy's change now got me thinking that this could be further improved into a stack allocated C array, to let the C compiler unroll the loop at will. I'll probably try that at some point... https://github.com/cython/cython/issues/2117 _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
