> From: steve+comp.lang.pyt...@pearwood.info
> Subject: Re: Beginner question
> Date: Tue, 4 Jun 2013 12:25:27 +0000
> To: python-list@python.org
>
> On Tue, 04 Jun 2013 14:53:29 +0300, Carlos Nepomuceno wrote:
>
> > That's exactly the same!
> >>>>dict(**{a:0,b:1})=={a:0,b:1}
> > True
>
>
> Of course it is. Isn't that what you wanted?
Indeed! But that form isn't economically viable as you noted.
>
> It's also a waste of time, because you create a dict literal using {},
> then unpack it into keyword arguments, then call dict() to create a new
> dict with the same content. Rather like doing this:
>
> n = int(str(42))
>
> only even more expensive.
>
>
> > Are there any benefits from using dict() instead of {}?
>
> Of course there are. {} can be used for creating dict literals, which
> means you are limited to key/values that you explicitly include. dict(),
> on the other hand, has a rich set of constructor APIs:
>
> py> help(dict)
>
> Help on class dict in module builtins:
>
> class dict(object)
> | dict() -> new empty dictionary
> | dict(mapping) -> new dictionary initialized from a mapping object's
> | (key, value) pairs
> | dict(iterable) -> new dictionary initialized as if via:
> | d = {}
> | for k, v in iterable:
> | d[k] = v
> | dict(**kwargs) -> new dictionary initialized with the name=value pairs
> | in the keyword argument list. For example: dict(one=1, two=2)
>
>
> py> dict(zip('abcd', range(4)), x=23, y=42, z=999)
> {'a': 0, 'c': 2, 'b': 1, 'd': 3, 'y': 42, 'x': 23, 'z': 999}
Awesome! Now I can do it just like that:
>>> dict([(chr(ord('a')+x),x) for x in range(2)])
{'a': 0, 'b': 1}
Thanks a lot! ;)
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