[Python-ideas] Possible method of distinguishing between set-literals, dict-literals, and odict-literals

[Ben Finney]

MRAB <python at mrabarnett.plus.com> writes:

> [for a literal OrderedDict,] How about ['a':'1', 'b':'2', 'c':'3']?

+1. That's quite good, and has symmetry with existing syntax::

    {'fred', 'barney', 4.75}    # unordered set
    ['fred', 'barney', 4.75]    # ordered list

    {'foo': 10.2, 'bar': 8.19}  # unordered dict
    ['foo': 10.2, 'bar': 8.19]  # ordered dict

That looks good to me.

> Ideally we would have [...] for ordered and {...} for unordered, with
> ':' if it's keyed:
> 
>     []  ordered,   value      (list)
>     [:] ordered,   key+value  (odict)
>     {}  unordered, value      (set)
>     {:} unordered, key+value  (dict)
> 
> It's too late to change that in Python 3.x, so it would have to be:
> 
>     []  ordered,   value      (list)
>     [:] ordered,   key+value  (odict)
>     {,} unordered, value      (set)
>     {}  unordered, key+value  (dict)

-0. Unlike syntax for creating and populating an instance, I actually
don't think we need to worry about having specific syntax for empty.

Compared to a non-empty container, it's quite a lower burden to simply
have an explicit call to the type constructor to create an empty
container.

-- 
 \       “Probably the toughest time in anyone's life is when you have |
  `\    to murder a loved one because they're the devil.” —Emo Philips |
_o__)                                                                  |
Ben Finney