How do I uncurry a function in Python?

Question

Recently, I have studied 'Programming language' using standard ML, and I've learned currying method(or something), so I applied it in Python. The below is simple function and currying.

def range_new(x, y):
    return [i for i in range(x, y+1)]

def curry_2(f):
    return lambda x: lambda y: f(x, y)

def uncurry_2(f):
    pass # I don't know it...

print(range_new(1, 10))
curried_range = curry_2(range_new)
countup = curried_range(1)
print(countup(10))
print(curried_range(1)(10))

The result is below. And it works well; with curry_2 we can make a new function(countup). But, then I want to make an uncurried function. However, I don't know how I can make it. How can I do it?

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Answer 1

The easiest solution is to wrap the curried function again with code that uncurries it:

def uncurry_2(f):
    return lambda x, y: f(x)(y)

uncurried_range = uncurry_2(curried_range)
print(uncurried_range(1, 10))

Answer 2

It's not exactly good style but you can access the variables in the closure using the (maybe CPython-only) __closure__ attribute of the returned lambda:

>>> countup.__closure__[0].cell_contents
<function __main__.range_new>

This accesses the content of the innermost closure (the variable used in the innermost lambda) of your function curry_2 and thus returns the function you used there.

However in production code you shouldn't use that. It would be better to create a class (or function) for currying that supports accessing the uncurried function (which is something lambda does not provide). However some functools in Python support accessing the "decorated" function, for example partial:

>>> from functools import partial
>>> countup = partial(range_new, 1)
>>> print(countup(10))
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> countup.func
<function __main__.range_new>