On 5 Feb 2009, at 23:54 , Steven D'Aprano wrote:
Raymond Hettinger wrote:
The arguments for and against the patch could be brought against
partial()
itself, so I don't understand the -1's at all.
Quite so, but that doesn't justify adding more capabilities to
partial().
I concur with Collin. Lever arguments are a road to bloat.
One person's "bloat" is another person's rich and complete toolbox.
> "In for a penny, in for a pound" is not a language design principle.
Neither are "slippery slope" arguments.
One of the real problems with partial() and its variants is that
they provide almost no advantage over an equivalent lambda.
How about speed? I don't have a recent version of Python here to
test, but my recollection is that partial is significantly faster
than lambda. And even if it currently isn't, there could be (is?)
more opportunity to optimize partial.
I guess that the voting on this is going to be fall along functional
lines: those who like functional languages will vote +1 on partial
and co, and those who don't will vote -1.
While I don't dislike partial(), I'd rather see one good use-case
for partial_right() to be removed: built-ins that don't accept
keywords. From Ben North's post starting this thread:
"I find 'functools.partial' useful, but occasionally I'm unable to
use it because it lacks a 'from the right' version. E.g., to create
a function which splits a string on commas, you can't say
# Won't work when called:
split_comma = partial(str.split, sep = ',')
and to create a 'log to base 10' function, you can't say
# Won't work when called:
log_10 = partial(math.log, base = 10.0)
because str.split and math.log don't take keyword arguments."
Wouldn't a `flip` function (reverse the order of the function's
arguments) be more flexible and general than a `partial_right` one?
Your first case would become
# we're not ignoring any argument, so we have to provide `maxsplit`
split_comma = partial(flip(str.split), None, ',')
and the second one would yield
log_10 = partial(flip(math.log), 10.0)
and if we only want to fill-in the rightmost argument, we can flip the
result to get the original order back:
split_5 = flip(partial(flip(str.split), 5))
While better kwargs support would be even better, there probably
always will be kwarg-less functions/methods, so the ability to
partially apply from the right stays interesting.
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
