Curried callables in Python!
Curried functions accept arguments one-by-one, instead of all in a single call. Some more functional languages provide more facilities for curried functions, but they have been missing in Python. If you've ever used
functools.partial, it's similar, but more potent.
curried function (also usable as a decorator) curries a function over the number of arguments it requires (which do not specify defaults). Optional arguments can be passed at any point in curried application as keywords.
>>> @curried ... def add(x, y, z=0): ... return x + y + z >>> add(4)(5) 9 >>> add(4, z=3)(5) 12
Curried functions that accept a variable number of arguments (i.e.
*args) need to be terminated by an empty call
>>> @curried ... def add_all(*nums): ... return reduce(lambda x,y: x+y, nums) >>> add_all(1)(2)(3)(4)() 10
Best of all, curried functions that don't accept variable positional arguments (
*args) can be treated exactly as if they were normal functions!
Even with functions decorated with
@curried, you need not treat them differently than if they were defined as normal functions, unless you want them to curry arguments. No need to worry about surprising or confusing colleagues! And, no strange curry/uncurry semantics!
>>> add(10, 20) 30 >>> add(10, 20, 30) 60 >>> add(10, 20, 30, 40) Traceback (most recent call last): File "<input>", line 1, in <module> File "curry.py", line 32, in curried_func return accum_curry(args, kwargs) File "curry.py", line 26, in accum_curry return func(*accum_args, **accum_kwargs) TypeError: add() takes at most 3 arguments (4 given)
Currently not uploaded to pypi, or even much of a package. The module's a single file with only two functions, so if you want to play around with it, drop it in as-is, and let me know what you think @ryanartecona!