Raymond Hettinger <[email protected]> added the comment:
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:
options.update(user_selections)
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.
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<https://bugs.python.org/issue36144>
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