Using Python 3 and Euclid’s algorithm to calculate the gcd of a list

Question

I am trying to use Euclid's algorithm to calculate the gcd of a list using Python 3. However, I get the error "TypeError: unsupported operand type(s) for %: 'NoneType' and 'int'". I checked everywhere, but still can not find what's wrong with my code. Here is my code,

# To get the gcd of a list
def gcd(numbers):
    m = numbers[0]
    for i in range(1, len(numbers)):
        m = gcd2(m, numbers[i])
    return m

# Use Euclid’s algorithm to calculate the gcd of two numbers
def gcd2(m, n):
    if m % n != 0:
        gcd2(n, m % n)
    else:
        return n

def main():
    str = [44, 6, 12, 24, 4, 18]
    print(gcd(str))

main()

Answer 1

You are missing a return statement on line 3 of gcd2. The updated function is below.

def gcd2(m, n):
    if m % n != 0:
        return gcd2(n, m % n)
    else:
        return n

Hope this helps.

Answer 2

def gcd2(m, n):
    if m % n != 0:
        gcd2(n, m % n)
    else:
        return n

In the if You aren't returning anything, so it defaults to None . Add return there.