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Author rhettinger
Recipients brandtbucher, gvanrossum, rhettinger, serhiy.storchaka, xtreak
Date 2019-02-28.07:36:52
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For the record, I'm opposed to the idea.

* Use of the + operator is a temptation to produce new dictionaries rather than update an existing dict in-place which is usually what you want.

* We already have ChainMap() which presents a single view of multiple mappings with any copying.

* It is natural to expect the plus operator to be commutative, but this operation would necessarily be non-commutative.

* Many other APIs are modeled on the dict API, so we should not grow the API unless there is a big win.  The effects would be pervasive.

* I don't see other languages going down this path, nor am I seeing dict subclasses that implement this functionality.  Those are indications that this more of a "fun thing we could do" rather than a "thing that people need".

* The existing code already reads nicely:


  That reads more like self explanatory English than:

     options += user_selections

  The latter takes more effort to correctly parse and
  makes it less clear that you're working with dicts.

* It isn't self-evident that the right operand needs to be another dictionary. If a person is trying to "add a key / value pair" to an existing dictionary, the "+=" operator would be tempting but it wouldn't work.
Date User Action Args
2019-02-28 07:36:52rhettingersetrecipients: + rhettinger, gvanrossum, serhiy.storchaka, xtreak, brandtbucher
2019-02-28 07:36:52rhettingersetmessageid: <>
2019-02-28 07:36:52rhettingerlinkissue36144 messages
2019-02-28 07:36:52rhettingercreate