Dictionary union (PEP 584) is merged

#1

Post by whalesalad » Tue, Feb 25, 2020, 8:08 PM UTC

Dictionary union (PEP 584) is merged
github.com

Re: Dictionary union (PEP 584) is merged

#2

Post by kam » Tue, Feb 25, 2020, 10:12 PM UTC

The PEP document describing the feature: https://www.python.org/dev/peps/pep-0584/

Re: Dictionary union (PEP 584) is merged

#3

Post by pansa2 » Tue, Feb 25, 2020, 10:24 PM UTC

kam wrote: post #2

The PEP document describing the feature: https://www.python.org/dev/peps/pep-0584/

> > Dict union will violate the Only One Way koan from the Zen.

> There is no such koan. "Only One Way" is a calumny about Python originating long ago from the Perl community.

Re: Dictionary union (PEP 584) is merged

#4

Post by seemslegit » Tue, Feb 25, 2020, 10:27 PM UTC

I wouldn't have thought about dict unpacking as a solution either but once suggested it seems satisfactory and I don't see how adding a new operator is more discoverable or natural than just putting this method in a more prominent place in the documentation.

Re: Dictionary union (PEP 584) is merged

#5

Post by Znafon » Tue, Feb 25, 2020, 10:39 PM UTC

seemslegit wrote: post #4

I wouldn't have thought about dict unpacking as a solution either but once suggested it seems satisfactory and I don't see how adding a new operator is more discoverable or natural than just putting this method in a more prominent place in the documentation.

Guido himself said he had forgotten about this trick and since it's syntactic sugar, it does not respect dict subclasses or other mappings.

Re: Dictionary union (PEP 584) is merged

#6

Post by seemslegit » Tue, Feb 25, 2020, 10:53 PM UTC

Znafon wrote: post #5

seemslegit wrote: post #4

I wouldn't have thought about dict unpacking as a solution either but once suggested it seems satisfactory and I don't see how adding a new operator is more discoverable or natural than just putting this method in a more prominent place in the documentation.

Guido himself said he had forgotten about this trick and since it's syntactic sugar, it does not respect dict subclasses or other mappings.

imo

  defaultdict(callback,{**a,**b})

is more readable than a | b without knowing that a or b are defaultdicts and having to reason about which default callback will be used

Re: Dictionary union (PEP 584) is merged

#7

Post by iddan » Tue, Feb 25, 2020, 11:00 PM UTC

FINALLY!

Re: Dictionary union (PEP 584) is merged

#8

Post by fyp » Tue, Feb 25, 2020, 11:04 PM UTC

  {**d1, **d2}

is very natural if you also write javascript where their spread operator looks like:

  {...d1, ...d2}

Re: Dictionary union (PEP 584) is merged

#9

Post by anentropic » Tue, Feb 25, 2020, 11:18 PM UTC

Nice

Re: Dictionary union (PEP 584) is merged

#10

Post by ptx » Tue, Feb 25, 2020, 11:19 PM UTC

Yay! I was wishing for this feature just a few days ago. It's somewhat analogous to how sorted (since Python 2.4) frees us from having to tediously make copies of lists to sort them in place.