Can lambda work with *args as its parameter? [duplicate]

Question

I am calculating a sum using lambda like this:

def my_func(*args):
    return reduce((lambda x, y: x + y), args)

my_func(1,2,3,4)

and its output is 10.

But I want a lambda function that takes random arguments and sums all of them. Suppose this is a lambda function:

add = lambda *args://code for adding all of args

someone should be able to call the add function as:

add(5)(10)          # it should output 15
add(1)(15)(20)(4)   # it should output 40

That is, one should be able to supply arbitrary number of parenthesis.

Is this possible in Python?

Answer 1

This is not possible with lambda, but it is definitely possible to do this is Python.

To achieve this behaviour you can subclass int and override its __call__ method to return a new instance of the same class with updated value each time:

class Add(int):
    def __call__(self, val):
        return type(self)(self + val)

Demo:

>>> Add(5)(10)
15
>>> Add(5)(10)(15)
30
>>> Add(5)
5
# Can be used to perform other arithmetic operations as well
>>> Add(5)(10)(15) * 100
3000

If you want to support floats as well then subclass from float instead of int.