dunder-docs (was Python is DOOMED! Again!)

[Rustom Mody]

On Sunday, February 1, 2015 at 10:15:13 AM UTC+5:30, Ethan Furman wrote:
> On 01/31/2015 07:16 PM, Steven D'Aprano wrote:
> > 
> > But by default, Python will fallback on __repr__ if __str__ doesn't exist,
> > or __str__ if __repr__ doesn't exist, or both. Or something. (I always
> > forget what the rules are exactly.)
> 
> If __str__ is missing, __repr__ is called.
> 
> If __repr__ is missing, object.__repr__ (or some intermediate base class' __repr__) is called.
> 
> --
> ~Ethan~

The other day I was taking a class in which I was showing
- introspection for discovering -- help, type, dir etc at the repl
- mapping of surface syntax to internals eg. a + b ←→ a.__add__(b)

And a student asked me the diff between
dir([])
and
[].__dir__()

I didnt know what to say...
Now surely the amount of python I dont know is significantly larger than what I know
Still it would be nice to have surface-syntax ←→ dunder-magic more
systematically documented