Currying decorator.

curry.py

from functools import partial, wraps
import doctest

def curry(f):
    """
    Allow partial evaluation of function (currying).

    Returns a `functools.partial` until all arguments are specified:

    >>> f = curry(lambda a,b: a + b)
    >>> assert type(f(1)) == partial
    >>> assert f(1)(1) == 2
    >>> assert f(1, 1) == 2

    Keeps default behaviour for keywords arguments, evaluating as
    soon as possible:

    >>> @curry
    ... def g(a, b, c=0):
    ...     "My docstring."
    ...     return a + b + c
    ...
    >>> assert type(g(1)) == partial
    >>> assert g(1)(1) == 2
    >>> assert g(1)(1, c=1) == 3
    >>> assert g.__doc__ == "My docstring."
    """

    @wraps(f)
    def curried_function(*args, **kwargs):
        if len(args) < f.func_code.co_argcount:
            return partial(f, *args, **kwargs)
        return f(*args)
    return curried_function

if __name__ == "__main__":
    doctest.testmod()