On Sat, Jul 27, 2019 at 9:28 PM Steven D'Aprano <st...@pearwood.info> wrote:
> If you're going to add support for a placeholder, there is no need to
> create a new kind of partial function?
>
Exactly! This is just an enhanced functools.partial. An enhancement that
has already been done in several 3rd party libraries, in fact. I like the
ellipsis, which most 3rd parties use, but it could be configurable what the
sentinel is. Maybe a default brand new `functools.SKIP` object, but with
the docs explaining the way to use the ellipsis for those 99% of users for
whom that wouldn't break anything.
Someone posted an example implementation that used a configurable
placeholder like this.
> > Sure we could also use a `lambda` instead
> I believe that partial is faster than lambda.
>
I don't really care about faster. I think the "partial with placeholder"
is simply nicer to read for many cases. Sure this is a toy, but:
>>> lastname = 'Mertz'
>>> greet_david = partial(print, ..., 'David', lastname) # In Python 3.9
>>> greet_david('Verwelkoming')
Verwelkoming David Mertz
vs.
>>> greet_david = lambda greeting: print(greeting, "David", lastname)
>>> greet_david('Cześć')
Cześć David Mertz
OK, that's a bad example because we are using it for the side effect too,
but I think it illustrates how the more flexible partial() would look
better than lambda.
--
Keeping medicines from the bloodstreams of the sick; food
from the bellies of the hungry; books from the hands of the
uneducated; technology from the underdeveloped; and putting
advocates of freedom in prisons. Intellectual property is
to the 21st century what the slave trade was to the 16th.
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