On Mon, Dec 14, 2020 at 9:11 AM Paul Sokolovsky <pmis...@gmail.com> wrote: > What would be the explanation for all that? > > > For reference, the disassembly of the 3 lines with CPython3.7 is > provided: > > 1 0 LOAD_NAME 0 (obj) > 2 LOAD_METHOD 1 (meth) > 4 CALL_METHOD 0 > 6 POP_TOP > > 2 8 LOAD_NAME 0 (obj) > 10 LOAD_METHOD 1 (meth) > 12 CALL_METHOD 0 > 14 POP_TOP > > 3 16 LOAD_NAME 0 (obj) > 18 LOAD_ATTR 1 (meth) > 20 STORE_NAME 2 (t) > 22 LOAD_NAME 2 (t) > 24 CALL_FUNCTION 0 > 26 POP_TOP > ...
Creating bound method objects can be expensive. Python has a history of noticing ways to improve performance without changing semantics, and implementing them. Details here: https://docs.python.org/3/library/dis.html#opcode-LOAD_METHOD If you force the bound method object to be created (by putting it in a variable), the semantics should be the same, but performance will be lower. Consider: rosuav@sikorsky:~$ python3.10 -c 'import dis; dis.dis(lambda obj: (obj.meth,)[0]())' 1 0 LOAD_FAST 0 (obj) 2 LOAD_ATTR 0 (meth) 4 BUILD_TUPLE 1 6 LOAD_CONST 1 (0) 8 BINARY_SUBSCR 10 CALL_FUNCTION 0 12 RETURN_VALUE rosuav@sikorsky:~$ python3.10 -c 'import dis; dis.dis(lambda obj: (obj.meth(),)[0])' 1 0 LOAD_FAST 0 (obj) 2 LOAD_METHOD 0 (meth) 4 CALL_METHOD 0 6 BUILD_TUPLE 1 8 LOAD_CONST 1 (0) 10 BINARY_SUBSCR 12 RETURN_VALUE rosuav@sikorsky:~$ python3.10 -m timeit -s 'x, f = 142857, lambda obj: (obj.bit_length(),)[0]' 'f(x)' 2000000 loops, best of 5: 101 nsec per loop rosuav@sikorsky:~$ python3.10 -m timeit -s 'x, f = 142857, lambda obj: (obj.bit_length,)[0]()' 'f(x)' 2000000 loops, best of 5: 124 nsec per loop rosuav@sikorsky:~$ python3.6 -m timeit -s 'x, f = 142857, lambda obj: (obj.bit_length(),)[0]' 'f(x)' 10000000 loops, best of 3: 0.124 usec per loop rosuav@sikorsky:~$ python3.6 -m timeit -s 'x, f = 142857, lambda obj: (obj.bit_length,)[0]()' 'f(x)' 10000000 loops, best of 3: 0.123 usec per loop Measurable improvement in 3.10, indistinguishable in 3.6. This is why lots of us are unimpressed by your strict mode - CPython is perfectly capable of optimizing the common cases without changing the semantics, so why change the semantics? :) ChrisA _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/5KBT5DI6NKKLS4QEDAYNIHKOFBGL7PFP/ Code of Conduct: http://python.org/psf/codeofconduct/
