[Python-ideas] An ABC representing "Iterable, Sized, Container"

[Alexander Heger]

>
> So maybe the solution really is to have a character type -- then a
> string is a sequence of characters, rather that a sequence of string,
> and all these problems go away.
>
> If a character object has all the methods of a string except indexing
> (and iterating) it might even be mostly backward compatible....
>
> Otherwise, special casing in multiple cases may be the only option.
>
> Or maybe all we need is a way to spell "any iterable of strings except
> a string", though that would only help type checking.
>

I agree, the fact that a string consists of strings has bothered me as
well.  It makes some things work well but some recursive algorithms
requires special checks.  There should be a way to iterate over a string as
characters.

AtomicIterable seems a good idea, but maybe it could be just the conceptual
starting point of building up a class hierarchy of "iterability", and such
a class could be passed to the 'flatten' method proposed above in the
thread by Nick Coghlan.

Some conceptual inspiration may be taken from numpy where one can have
0-dimensional arrays which are different from scalars - and different from
n-D array with 1 element (n > 0)

```
In [7]: x = np.ndarray(())

In [8]: x
Out[8]: array(21.0)

In [9]: type(x)
Out[9]: numpy.ndarray

In [10]: x[()]
Out[10]: 21.0

In [11]: np.asscalar(x)
Out[11]: 21.0

 In [13]: x = np.ndarray((1,))

In [14]: x
Out[14]: array([ 17.5])
```
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