Python: Why “return” won´t print out all list elements in a simple for loop and “print” will do it?

Question

Im trying to print out all elements in a list, in Python, after I´ve appended one list to another. The problem is that it only prints out every element when I use PRINT inst

Answer 1

def union(a,b):
    a.extend(b)
    for item in a:
        print item,
    return a


a=[1,2,3,4]
b=[4,5,6]
union(a,b)

prints

1 2 3 4 4 5 6