[Python-Dev] Unbound locals in class scopes
ron3200 at gmail.com
Sat Jun 20 18:12:57 CEST 2015
On 06/20/2015 02:51 AM, Ivan Levkivskyi wrote:
> There appeared a question in the discussion on
> http://bugs.python.org/issue24129 about documenting the behavior that
> unbound local variables in a class definition do not follow the normal rules.
> Guido said 13 years ago that this behavior should not be changed:
> however, things changed a bit in Python 3.4 with the introduction of the
> LOAD_CLASSDEREF opcode. I just wanted to double-check whether it is still a
> desired/expected behavior.
Guido's comment still stands as far as references inside methods work in
regards to the class body. (they must use a self name to access the class
name space.) But the execution of the class body does use lexical scope,
otherwise it would print xtop instead of xlocal here.
x = "xtop"
y = "ytop"
x = "xlocal"
y = "ylocal"
y = 1
Maybe a better way to put this is, should the above be the same as this?
>>> x = "xtop"
>>> y = "ytop"
>>> def func():
... x = "xlocal"
... y = "ylocal"
... def _C():
... y = 1
... return locals()
... C = type("C", (), _C())
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 9, in func
File "<stdin>", line 6, in _C
UnboundLocalError: local variable 'y' referenced before assignment
I think yes, but I'm not sure how it may be different in other ways.
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