The following PR replaces the sequence of statement d = d1.copy() d.update(d2) (where d1 and d2 are dicts) with a form proposed in PEP 448: d = {**d1, **d2} or equivalent. Besides functools, where using the new syntax makes the code clearer, there are not much occurrences of such idiom: only in yet 5 files, 1-2 times per file.
3 years ago, Trey Hunter found 11 ways to merge to a new dict. https://treyhunner.com/2016/02/how-to-merge-dictionaries-in-python/ He followed up with a performance comparison. https://gist.github.com/treyhunner/f35292e676efa0be1728 ** unpacking was nearly twice as fast as the 2nd place methods. (Bigger dict might change the ratio, but I expect ** unpacking to remain first.) Trey's summary: "This is simple and Pythonic. There are quite a few symbols, but it’s fairly clear that the output is a dictionary at least." I consider the last point a major plus. User comment: "Beautiful. Pythonic. Thank you." No negatives.
