Question

def test(x,theList): 
    theList.append(x) 
    if x < 2: 
        x = x + 1 
        test(x,theList) 
        print x 
        print theList 

test(1,[]) 

Why is the result [1,2]? And not only [1]?

Answer 1

Because you execute the print statement after the recursive call to test() returns.

Python objects are always passed by reference, so when the second invocation of test calls theList.append(x), it is appending to the original list that was passed in, which is what you then print.