What is a subtraction function that is similar to sum() for subtracting items in list?

I am trying to create a calculator, but I am having trouble writing a function that will subtract numbers from a list.
For example:

class Calculator(object):
    def __init__(self, args):
        self.args = args

    def subtract_numbers(self, *args):
        return ***here is where I need the subtraction function to be****

For addition, I can simply use return sum(args) to calculate the total but I am unsure of what I can do for subtractions.