exec "x = 3; print x" in a - How does it work?

[Veek. M]

Ben Finney wrote:

> "Veek. M" <vek.m1234 at gmail.com> writes:
> 
>> What is the return value of `exec`?
> 
> You can refer to the documentation for questions like that.
> <URL:https://docs.python.org/3/library/functions.html#exec>
> 
>> Would that object be then used to iterate the sequence in 'a'?
> 
> The ‘for’ or ‘while’ statements are correct for iteration.
> 
>> I'm reading this:
>> https://www.python.org/download/releases/2.2.3/descrintro/
> 
> Why?
> 
Well, i had a question on MRO and asked on freenode #python and they 
suggested i read that.

My question was:
class A(x, y, z):
 pass

class x(q,w,r)
 pass

I wanted to know how the __mro__ would be generated (c3 linearization)

I had assumed when using super() it would do:
x, q, w, r, y, z, object
basically hit a base class and finish with all it's parents before 
stepping to the next sibling

But then i read somewhere else that it's like this:
x, y, z, q, w, r, object
and of course if q has base-classes then:
x, y, z, q, w, r, e, f, g
which is utterly confusing because you can't tell by looking where e, f, 
g are coming from (q) in this case..

This doc: 
https://rhettinger.wordpress.com/2011/05/26/super-considered-super/
I was getting all cross-eyed reading this:
'The ancestor tree for our new class is: LoggingOD, LoggingDict, 
OrderedDict, dict, object. For our purposes, the important result is 
that OrderedDict was inserted after LoggingDict and before dict! This 
means that the super() call in LoggingDict.__setitem__ now dispatches 
the key/value update to OrderedDict instead of dict.'

I was wondering why they had chosen this notation over the other.

And if you're wondering why that paper - because i was reading Beazley 
super() pg 120 and the whole hard-coding avoided using super() bit.