Just to add to the discussion this was brought up previously as part of PEP 448 unpacking generalizations that also added {**x, **y} to merge two dicts in Python 3.5.

Previous python ideas thread : https://mail.python.org/pipermail/python-ideas/2015-February/031748.html
LWN summary : https://lwn.net/Articles/635397/

The previous thread is worth reading as some of the points still stand even with {**x, **y} added.

On Wed, Feb 27, 2019 at 9:59 PM João Matos <jcrmatos@gmail.com> wrote:

I would like to propose that instead of using this (applies to Py3.5 and upwards)
dict_a = {**dict_a, **dict_b}

we could use
dict_a = dict_a + dict_b

or even better
dict_a += dict_b

Best regards,

João Matos
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Karthikeyan S