[issue45542] Using multiple comparison operators can cause performance issues
New submission from Maja : For example: def f(x): return 1 < x < 3 will be slower than: def f(x): return 1 < x and x < 3 The first function will generate following bytecode: 0 LOAD_CONST 1 (1) 2 LOAD_FAST0 (x) 4 DUP_TOP 6 ROT_THREE 8 COMPARE_OP 0 (<) 10 JUMP_IF_FALSE_OR_POP18 12 LOAD_CONST 2 (3) 14 COMPARE_OP 0 (<) 16 RETURN_VALUE >> 18 ROT_TWO 20 POP_TOP 22 RETURN_VALUE Performs unnecessary stack operations: duplicates x, rotates 3 items for no reason, then re-rotates 2 items and pops a value. This is fine if the value in the middle was more complex and needed to be duplicated rather than recalculated, which would be definitely slower, but for simpler values like names or constants, it's actually bad. The bytecode for the first function should look the same as second one which is: 0 LOAD_CONST 1 (1) 2 LOAD_FAST0 (x) 4 COMPARE_OP 0 (<) 6 JUMP_IF_TRUE_OR_POP 14 8 LOAD_FAST0 (x) 10 LOAD_CONST 2 (3) 12 COMPARE_OP 0 (<) >> 14 RETURN_VALUE -- components: Interpreter Core messages: 404508 nosy: akuvfx priority: normal severity: normal status: open title: Using multiple comparison operators can cause performance issues type: performance versions: Python 3.11 ___ Python tracker <https://bugs.python.org/issue45542> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue45542] Using multiple comparison operators can cause performance issues
Change by Maja : -- keywords: +patch pull_requests: +27377 stage: -> patch review pull_request: https://github.com/python/cpython/pull/29109 ___ Python tracker <https://bugs.python.org/issue45542> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue25450] Save path automatically choses C:\Windows\system32
New submission from Maja Tomic: I'm teaching kids to code in Python. Today we had two boys, one with Windows 8, the other one with Windows 10. In both cases Python 3.5 was installed and the automatic path where files are saved was C:\Windows\system32. This wasn't possible, since it cannot be written to. Yet, the boys tried to save files to it. In the Windows 8-case the file did not get saved. Yet, IDLE still refered to the file as having an error (it couldn't find the turtle package because the file was called turtle.py - we got that right eventually). Even after reinstalling Python it still refered to the non-existing file and the error in it. We changed the path and it solved the problem. Hope this can be fixed. -- components: Installation messages: 253257 nosy: Maja Tomic priority: normal severity: normal status: open title: Save path automatically choses C:\Windows\system32 type: behavior versions: Python 3.5 ___ Python tracker <http://bugs.python.org/issue25450> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
