Question

I’m stunned with this function I’ve written for python. I’ve observed that in the lower while it changes the values in the list vctor even though that list is not touched along the function. I’ve passed the pair (10, [1,3,5,7,10]) and it has changed the list vctor to [1,3,5,8,10]. Is there an explanation for this?

def siguiente(k,vctor):
    l = len(vctor)
    vctorsig = vctor
    i = l-1
    while i>= 0:    
        if vctorsig[i] <= k - l + i: 
            j=i
            while j<=l-1:
                print vctor
                vctorsig[j] = vctor[i]+j-i+1
                j=j+1
            i = -1
        else:
            i = i-1
    return vctorsig    

Answer 1

When you do vctorsig = vctor, you are making vctorsig a reference to the list referenced by vctor, so when you modify it, you modify the original list.

If you wish to copy the list there, you can simply do vctorsig = list(vctor).