Georg Brandl wrote:

Nick Coghlan schrieb:

...

2. Method lookup MAY bypass __getattribute__, shadowing the attribute in the instance dictionary MAY have ill effects. (slots such as __enter__ and __exit__ that are looked up via normal attribute lookup in CPython will fit into this category)

I would argue that the __enter__ and __exit__ behavior should be changed too. The reason for the current behavior is this:

2 0 LOAD_GLOBAL 0 (a) 3 DUP_TOP 4 LOAD_ATTR 1 (__exit__) 7 STORE_FAST 0 (_[1]) 10 LOAD_ATTR 2 (__enter__) 13 CALL_FUNCTION 0 16 STORE_FAST 1 (_[2]) 19 SETUP_FINALLY 18 (to 40)

IOW, when "with" is compiled, the attributes are retrieved using bytecode. It wouldn't be hard to have a WITH_SETUP opcode (along with the already existing WITH_CLEANUP) that would make the bytecode read like:

2 0 LOAD_GLOBAL 0 (a) 3 WITH_SETUP 0 (_[1]) 6 STORE_FAST 1 (_[2]) 9 SETUP_FINALLY 18 (to 40)

No argument here - the PEP 343 implementation is the way it is mainly because it involved the least messing around with the performance-sensitive ceval loop. That said, the with statement implementation is already a bit different in 2.6/3.0 (it moves things around on the stack so it can avoid the STORE_FAST/LOAD_FAST/DELETE_FAST operations): def f(): with a: pass Python 2.5 disassembly: 2 0 LOAD_GLOBAL 0 (a) 3 DUP_TOP 4 LOAD_ATTR 1 (__exit__) 7 STORE_FAST 0 (_[1]) 10 LOAD_ATTR 2 (__enter__) 13 CALL_FUNCTION 0 16 POP_TOP 17 SETUP_FINALLY 4 (to 24) 20 POP_BLOCK 21 LOAD_CONST 0 (None) >> 24 LOAD_FAST 0 (_[1]) 27 DELETE_FAST 0 (_[1]) 30 WITH_CLEANUP 31 END_FINALLY Python 2.6 disassembly: 2 0 LOAD_GLOBAL 0 (a) 3 DUP_TOP 4 LOAD_ATTR 1 (__exit__) 7 ROT_TWO 8 LOAD_ATTR 2 (__enter__) 11 CALL_FUNCTION 0 14 POP_TOP 15 SETUP_FINALLY 4 (to 22) 18 POP_BLOCK 19 LOAD_CONST 0 (None) >> 22 WITH_CLEANUP 23 END_FINALLY Cheers, Nick. -- Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia --------------------------------------------------------------- http://www.boredomandlaziness.org