Plumbing behind super()
On Thu, Jun 27, 2019, at 23:32, adam.preble at gmail.com wrote:
> On Thursday, June 27, 2019 at 8:30:21 PM UTC-5, DL Neil wrote:
> > I'm mystified by "literally given nothing".
> I'm focusing there particularly on the syntax of writing "super()"
> without any arguments to it. However, internally it's getting fed stuff.
Any function which is defined inside a class and accesses 'super' is provided a 'cell variable' (i.e. nonlocal) called __class__, which super inspects on the stack to identify the class (along with finding the self argument)
>>> class C:
... def foo(): super
(<cell at 0x0000024105737168: type object at 0x00000241036CD0D8>,)
You can also provide this cell manually by defining it as a nested function inside another function which has a local variable __class__.
>>> def bar():
... __class__ = C
... return lambda self: super()
<super: <class 'C'>, <C object>>
You can see all this happening in https://github.com/python/cpython/blob/3.8/Objects/typeobject.c#L7812