Adrian Holovaty wrote:
> On 9/6/06, Martin <[EMAIL PROTECTED]> wrote:
>> def curry(fct, *args, **kwargs):
>> def _curried(*moreargs, **morekwargs):
>> return fct (* (args+moreargs), **dict(kwargs, ** morekwargs))
>> return _curried
>>
>> It's just a performance issue (saving a few list operations) andbecause
>> I have to use CGI I care about performance at bit more than others ...
>
> Thanks for the great catch and fix, Martin! I've checked in your
> change in changeset 3733. Please do let us know if you find any other
> places we could optimize.
>
> Adrian
>
Martin's version is indeed faster, but has a 'gotcha' in that it precludes
passing a keyword arguments named 'fct' to a curried function...
>>> def curry1(*args, **kwargs):
... def _curried(*moreargs, **morekwargs):
... return args[0](*(args[1:]+moreargs), **dict(kwargs.items() +
... morekwargs.items()))
... return _curried
...
...
>>> def curry2(fct, *args, **kwargs):
... def _curried(*moreargs, **morekwargs):
... return fct (* (args+moreargs), **dict(kwargs, ** morekwargs))
... return _curried
...
Check the speed up...
>>> def adder(a,b,c,d):
... return a+b+c+d
...
>>> adder_cur1 = curry1(adder, 1, 2)
>>> adder_cur2 = curry2(adder, 1, 2)
>>> shell.timefunc(adder_cur1, 3, 4)
'_curried(...) 37276 iterations, 13.41usec per call'
>>> shell.timefunc(adder_cur2, 3, 4)
'_curried(...) 54986 iterations, 9.09usec per call'
which is about 30% faster in this case
However...
>>> def adder2(a,b,c,d, fct=sum):
... return fct([a,b,c,d])
...
>>> import sys
>>> p1 = curry1(1,2, fct="".join)
>>> p2 = curry2(1,2, fct="".join)
...
Traceback (most recent call last):
File "<input>", line 1, in ?
TypeError: curry2() got multiple values for keyword argument 'fct'
>>>
Oops.
Better to rename fct to something less likely to clash, such as _curried_fct
If you're really hunting for speed, there is a significant boost available in
the common special case of a python function curried with one positional
argument. In this case, you can [ab]use the method binding machinery, e.g.:
def curry3(_curried_fct, *args, **kwargs):
if len(args) == 1:
# Special case where we try to abuse the descriptor
try:
return _curried_fct.__get__(args[0])
except AttributeError:
# built-ins fail - handle them in the normal way
pass
def _curried(*moreargs, **morekwargs):
return _curried_fct (*(args+moreargs), **dict(kwargs, ** morekwargs))
return _curried
This is about twice as fast as curry2 for the case of a python function curried
with one argument. It also offers better introspection than either curry1 or
curry2, since the original signature is preserved. It's a bigger change than
the curry2 though, since it changes the type of the curry from function to
bound
method.
Michael
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