On Mon, Jul 4, 2016 at 9:20 PM, Steven D'Aprano <st...@pearwood.info> wrote: > I got this in Python 3.6: > > > py> class A: > ... var = 999 > ... print(var) # succeeds > ... class B: > ... x = var > ... > 999 > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > File "<stdin>", line 3, in A > File "<stdin>", line 4, in B > NameError: name 'var' is not defined > > > I expected that `var` would be available during the construction of B, just > as it was available inside A, but not to methods inside B. Obviously my > expectations are invalid. Can anyone explain the actual behaviour?
Class definitions don't create closures like functions do. When Python executes a class definition, the metaclass creates a dict, and then the interpreter execs the class body using that dict as the locals. The body of class A has one locals dict, and the body of class B has a completely separate locals dict. The only way to share variables between them (prior to the class objects actually being constructed) is via globals. -- https://mail.python.org/mailman/listinfo/python-list
