Issue 1863: NameError with genexp in class scope (original) (raw)

Issue1863

Created on 2008-01-17 21:03 by cptnwillard, last changed 2022-04-11 14:56 by admin. This issue is now closed.

Messages (7)
msg60060 - (view)	Author: Willard (cptnwillard)	Date: 2008-01-17 21:03
The following code does not work like expected, it triggers a NameError. class C: a = 42 list(a for _ in 'x') >>> NameError: global name 'a' is not defined This issue was discussed on comp.lang.python in the thread "Is this a bug, or is it me?".
msg60066 - (view)	Author: Guido van Rossum (gvanrossum) *	Date: 2008-01-17 22:06
It's a weakness, not a bug. Just use a different variable name besides 'a'.
msg60068 - (view)	Author: Raymond Hettinger (rhettinger) *	Date: 2008-01-17 22:32
I don't follow what you mean. Can you post a working version of the code fragment?
msg60092 - (view)	Author: Facundo Batista (facundobatista) *	Date: 2008-01-18 14:02
Don't follow you: >>> class C: a = 42 list(a for _ in 'x') >>> Works here! (Python 2.5.1 on win32)
msg60094 - (view)	Author: Amaury Forgeot d'Arc (amaury.forgeotdarc) *	Date: 2008-01-18 14:19
Facundo, are your sure that your output starts from a fresh environment? I get: C:\Python25>python Python 2.5.1 (r251:54863, Apr 18 2007, 08:51:08) [MSC v.1310 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> class C: ... a = 42 ... list(a for _ in 'x') ... Traceback (most recent call last): File "", line 1, in File "", line 3, in C File "", line 3, in NameError: global name 'a' is not defined This error is actually approximately "documented" in an obscure sentence in http://docs.python.org/dev/reference/executionmodel.html#naming """ The scope of names defined in a class block is limited to the class block; it does not extend to the code blocks of methods. """ Well, I'm not sure that the genexpr can be considered as a "method", but it is certainly a nested code block.
msg60100 - (view)	Author: Facundo Batista (facundobatista) *	Date: 2008-01-18 16:33
Yes, something was bad with my test. Now I have the same behaviour. Sorry for the noise.
msg60101 - (view)	Author: Georg Brandl (georg.brandl) *	Date: 2008-01-18 16:44
Amaury Forgeot d'Arc schrieb: > Well, I'm not sure that the genexpr can be considered as a "method", but > it is certainly a nested code block. Technically it is a method, that's why this happens. I added a note to the docs in r60051; closing this as "won't fix".