[Python-ideas] Adding "+" and "+=" operators to dict

[Petr Viktorin]

I don't see ChainMap mentioned in this thread, so I'll fix that:

On Thu, Feb 12, 2015 at 2:32 PM, Juancarlo Añez <apalala at gmail.com> wrote:

> most common cases would be:
>
>
>     new_dict = a + b
>     old_dict += a

In today's Python, that's:
from collections import ChainMap
new_dict = dict(ChainMap(b, a))
old_dict.update(a)

>>     new_dict = {}
>>     for old_dict in (a, b, c, d):
>>         new_dict.update(old_dict)
>
>
> It would be easier if we could do:
>
>     new_dict = {}
>     new_dict.update(a, b, c, d)
>
> It would also be useful if dict.update() returned self, so this would be
> valid:
>
>     new_dict = {}.update(a, b, c, d)

In today's Python:
new_dict = dict(ChainMap(d, b, c, a))

Many uses don't need the dict() call – e.g. when passing it **kwargs,
or when it's more useful as a view.

Personally, the lack of a special operator for this has never bothered me.