How to use result of function as an argument of the same function multiple times?

Question

I have a simple algorithm which calculate GCD for 2 integers. What I'm trying to do is to use result of this function to calculate GCD for more then 2 integers. For example GCD for 99 and 22 is 11. Then I want to use 11 as first integer and some number. The thing is I don't know how to use a first result to calculate another one. Especially if there are more then 3 integers because user decides for how many of them the GCD will be calculated. Here is my code (which work only for 2 integers):

required_inputs = int(input("For how many numbers would you like to find their GCD?: "))
received_inputs = []

for num in range(0, required_inputs):
    values = int(input())
    received_inputs.append(values)
if len(received_inputs) == 0:
    values = int(input())
    received_inputs.append(values)

def GCD(a, b):
    if b == 0:
        return a
    else:
        return GCD(b, a % b)

print(GCD(received_inputs[0], received_inputs[1]))

Answer 1

If the idea is to use recursion for combining the results as well as in the algorithm itself then this will work:

def GCD(*numbers):
    a, b = numbers[:2]
    if len(numbers) == 2:
        if b == 0:
            return a
        else:
            return GCD(b, a % b)
    else:
        return GCD(GCD(a, b), *numbers[2:])


print(GCD(*received_inputs))

Another options include a loop (ok) or using functools.reduce (not recommended as not readable enough).

Answer 2

Sounds like you are talking about recursion:

https://www.programiz.com/python-programming/recursion

Basically you just do another call to the same method, inside of that method:

def calc_factorial(x):
    """This is a recursive function
    to find the factorial of an integer"""

    if x == 1:
        return 1
    else:
        return x * calc_factorial(x - 1)

num = 4
print("The factorial of {} is {}".format(num, calc_factorial(num)))