The Empty List Blocks Recursion

[leoahum]

I'm not sure I understand the question. If you have a K in the function as a non-empty list, append will add to what is already in the list. But if you are defining K in the function, you will have the same problem of it resetting every time you recurse. But if you have a default, and pass the modified list each time you recurse, it doesn't reset.

Thank you! It is very helpful. I think I figured it out.

List = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
step = 4



def ResetCR (l, stp, K = None):
    if K is None:
        K = []
    if stp != 0:
        for i in range(1, int(len(l)/stp)+1):
            K.append(l[i*stp - 1])
        l = [x for x in l if x not in K]
        stp = stp - 1
        return ResetCR(l,stp,K)
    if stp == 0:
        return K


F = ResetCR(List,step)

print (F)