Question

I have taken a piece of code from http://www.s-anand.net/euler.html, problem 5:

def gcd(a,b): 
    print a,b
    return b and gcd(b, a % b) or a

print gcd(10,20)

Giving output:

10 20

20 10

10 0

10

Why the last line prints only “a” not b.

Can you please explain how the return statement in above code works.

I am little bit confused with “and” and “or” operators.

Answer 1

b and gcd(b, a % b) or a

was the old way of writing:

gcd(b, a % b) if b else a