[Python-Dev] performance of {} versus dict()

Chris Angelico rosuav at gmail.com
Thu Nov 15 00:40:20 CET 2012

On Thu, Nov 15, 2012 at 10:36 AM, Steven D'Aprano <steve at pearwood.info> wrote:
> On 15/11/12 05:54, Mark Adam wrote:
>> Merging of two dicts is done with dict.update.   How do you do it on
>> initialization?  This doesn't make sense.
> Frequently.
> my_prefs = dict(default_prefs, setting=True, another_setting=False)
> Notice that I'm not merging one dict into another, but merging two dicts
> into a third.

Side point: Wouldn't it be quite logical to support dict addition?

>>> {"a":1}+{"b":2}
Traceback (most recent call last):
  File "<pyshell#59>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'dict' and 'dict'

It would make sense for this to result in {"a":1,"b":2}.


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