On Tue, Nov 24, 2009 at 4:31 AM, Rob Williscroft <r...@freenet.co.uk> wrote: > mk wrote in news:mailman.915.1259064240.2873.python-l...@python.org in > comp.lang.python: > >> >> def pythonic(): > >> def unpythonic(): > > >> Decidedly counterintuitive: are there special optimizations for "if >> nonevar:" type of statements in cpython implementation? >> > > from dis import dis > > dis( unpythonic ) > > 18 31 LOAD_FAST 0 (nonevar) > 34 LOAD_CONST 0 (None) > 37 COMPARE_OP 9 (is not) > 40 JUMP_IF_FALSE 4 (to 47) > > dis( pythonic ) > > 11 31 LOAD_FAST 0 (nonevar) > 34 JUMP_IF_FALSE 4 (to 41)
In other words, CPython doesn't happen to optimize `if nonevar is not None` as much as it theoretically could (which would essentially require a JUMP_IF_NONE opcode). Since CPython isn't known for doing fancy optimizations, this isn't surprising. Cheers, Chris -- http://blog.rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
