fCONV_AUSRICHTG is not defined - Why?

[Egon Frerich]

Am 07.11.23 um 20:10 schrieb MRAB via Python-list:
> On 2023-11-07 18:30, dn via Python-list wrote:
>> On 08/11/2023 06.47, Egon Frerich via Python-list wrote:
>>> I've no idea why this happens. In a module there are lists and 
>>> definitions:
>> ...
>>
>>>      ["%s%s%s " % (i[fCONV_AUSRICHTG], i[fLG2], i[fTYP]) for i in 
>>> Felder])
>>>    File "/home/egon/Entw/Geldspur/geldspur/gui/GUI_Konfig.py", line 
>>> 90, in <listcomp>
>>>      ["%s%s%s " % (i[fCONV_AUSRICHTG], i[fLG2], i[fTYP]) for i in 
>>> Felder])
>>> NameError: name 'fCONV_AUSRICHTG' is not defined
>>>
>>> You see "Felder" and with "0 0 3 4" the correct value 4 for 
>>> fCONV_AUSRICHTG. But there is the NameError.
>>>
>>> What does <listcomp> mean? Is there a change from python2 to python3?
>>
>> Works for me (Python 3.11 on Fedora-Linux 37)
>> - both as a script, and simple/single import.
>>
>> What happens when you extract the second dimension's definitions into a
>> module of their own, and import that (with/out less-sophisticated join)?
>>
> The missing detail is this line from the traceback:
>
>    File "/home/egon/Entw/Geldspur/geldspur/gui/GUI_Konfig.py", line 11,
> in <module>
>      class GUIcfg:
>
You are right. The list comprehension has to be outside the class. The 
scope rules have been changed python2 and python3.

Egon



> Here's a small example that shows the problem:
>
> ----8<----
> #!python3.11
> # -*- encoding: utf-8 -*-
>
> class Test:
>     hello = "hello"
>     print(hello)
>     print([[zero] for _ in range(4)])
> ----8<----
>
> and its traceback:
>
> ----8<----
> hello
> Traceback (most recent call last):
>   File "C:\Projects\regex3\test_clipboard.py", line 4, in <module>
>     class Test:
>   File "C:\Projects\regex3\test_clipboard.py", line 7, in Test
>     print([zero for _ in range(4)])
>          ^^^^^^^^^^^^^^^^^^^^^^^^^^
>   File "C:\Projects\regex3\test_clipboard.py", line 7, in <listcomp>
>     print([zero for _ in range(4)])
>            ^^^^
> NameError: name 'zero' is not defined
> ----8<----
>
> 'zero' is visible in:
>
>     print(hello)
>
> but not in:
>
>     print([zero for _ in range(4)])
>
> Something to do with how scoping is implemented in comprehensions?
>