LGTM, but import hashlib ... hashlib.sha512() can be a tiny bit faster.

Well, I wanted to minimize changes. I'm surprised that it's faster. Is it really faster? :-) To be honest, I have no preference.

I ran a quick micro-benchmark:

$ python3 -m perf timeit -o from.json -v -s 'import hashlib' 'from hashlib import sha256'
$ python3 -m perf timeit -o import.json -v -s 'import hashlib' 'import hashlib; hashlib.sha256'
$ python3 -m perf compare_to import.json from.json 
Mean +- std dev: [import] 123 ns +- 3 ns -> [from] 684 ns +- 10 ns: 5.54x slower (+454%)

Oh, I'm surprised by these numbers. So yeah, "import hashlib; hashlib.sha256" is near 6x faster than "from hashlib import sha256". It doesn't make sense to me, since the 2 code should be the same.

I have created the alternative PR #12742. It's a good compromise between Victor's need for speed and Raymond's wish for simple code.

It doesn't make sense to me, since the 2 code should be the same.

They are not the same. In the second case it calls the Python code to handle non-empty from list.

@rhettinger merged PR #12742, so I close my PR.