On 29 December 2016 at 18:35, Chris Angelico <ros...@gmail.com> wrote:
> On Thu, Dec 29, 2016 at 7:20 PM, Steven D'Aprano <st...@pearwood.info>
> wrote:
> > I'd rather add a generator to the itertools
> > module:
> >
> > itertools.iterhash(iterable) # yield incremental hashes
> >
> > or, copying the API of itertools.chain, add a method to hash:
> >
> > hash.from_iterable(iterable) # return hash calculated incrementally
>
> The itertools module is mainly designed to be consumed lazily. The
> hash has to be calculated eagerly, so it's not really a good fit for
> itertools.
I understood the "iterhash" suggestion to be akin to itertools.accumulate:
>>> for value, tally in enumerate(accumulate(range(10))): print(value,
tally)
...
0 0
1 1
2 3
3 6
4 10
5 15
6 21
7 28
8 36
9 45
However, I think including Ned's recipe (or something like it) in
https://docs.python.org/3/reference/datamodel.html#object.__hash__ as a
tool for avoiding large temporary tuple allocations may be a better way to
start off as:
1. It's applicable to all currently released versions of Python, not just
to 3.7+
2. It provides more scope for people to experiment with their own variants
of the idea before committing to a *particular* version somewhere in the
standard library
Cheers,
Nick.
--
Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia
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