Issue 26825: Variable defined in exec(code) unreachable inside function call with visible name in dir() results (original) (raw)

Issue26825

Created on 2016-04-22 06:54 by 324857679, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Messages (3)
msg263967 - (view)	Author: ganix (324857679)	Date: 2016-04-22 06:54
here is a code show what happend: >>> def func(): exec('ans=1') print(dir()) return ans >>> func() ['ans'] Traceback (most recent call last): File "<pyshell#5>", line 1, in func() File "<pyshell#4>", line 4, in func return ans NameError: name 'ans' is not defined i tried this code in version 2.7,it is ok
msg263984 - (view)	Author: Xiang Zhang (xiang.zhang) *	Date: 2016-04-22 08:43
This seems to a behaviour change. In 2.7, return ans compiles to LOAD_NAME so it can find ans. But in 3.x, it compiles to LOAD_GLOBAL which searches ans from global scope. I don't know when this change is introduced.
msg263986 - (view)	Author: Eryk Sun (eryksun) *	Date: 2016-04-22 09:01
In Python 2, using the exec statement makes the compiler disable fast locals: >>> def foo(): pass ... >>> def bar(): exec '' ... >>> foo.__code__.co_flags & inspect.CO_OPTIMIZED 1 >>> bar.__code__.co_flags & inspect.CO_OPTIMIZED 0 This has never been the case in Python 3, in which exec() is a function instead of a statement. The exec function can be shadowed by a global named "exec", so the hack to disable fast locals was removed.