[Python-Dev] Possible patch for functools partial - Interested?
Steve Holden
steve at holdenweb.com
Fri May 7 19:57:06 CEST 2010
Steven D'Aprano wrote:
> On Sat, 8 May 2010 02:07:55 am Rob Cliffe wrote:
>> Sorry to grouse, but isn't this maybe being a bit too clever?
>> Using your example,
>> p1 = partial(operator.add)
>> is creating a callable, p1, i.e. a sort of function. Yes I know
>> technically it's not a function, but it behaves very much like one.
>>
>> Now, if I write
>>
>> def f1(x,y): return x+y
>> def f2(x,y): return x+y
>>
>> I don't expect f1==f2 to be True, even though f1 and f2 behave in
>> exactly the same way,
>> and indeed it is not.
>
> I do expect f1==f2, and I'm (mildly) disappointed that they're not.
>
How about
def f1(x, y): return x+y
def f2(x, y): return y+x
As you know, there are limits to everything. It seems to me that while
pure mathematics can (sometime) easily determine functional equivalence,
once you get to code it's a lot harder because there are semantic
constraints that don't apply in pure mathematics.
>
> [...]
>> Similarly, if you wanted p1==p2, why not write
>>
>> p1 = partial(operator.add)
>> p2 = p1
>
> I thought the OP gave a use-case. He's generating "jobs" (partial
> applied to a callable and arguments), and wanted to avoid duplicated
> jobs.
>
> I think it is reasonable to expect that partial(operator.add, 2)
> compares equal to partial(operator.add, 2). I don't think he's
> suggesting it should compare equal to partial(lambda x,y: x+y, 2).
>
Which absence, presumably, also mildly disappoints you?
regards
Steve
> +0.5 on comparing equal.
> +1 on a nicer repr for partial objects.
>
>
>
--
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