How to run a statement exactly once in recursion function

Question

I want to make a copy of list in recursion function

def rec(I: List[int]) -> List[int]:
    new_lst = I[:] # <- want to do this only on first call of rec in recursive stack
    # ....(new_lst is edited)

    rec(new_lst)
    return new_lst

Answer 1

One solution is to wrap it in an initializer function, then call that initializer function instead:

def rec(I: List[int]) -> List[int]:
    ....(new_lst is edited)

    rec(new_lst)
    return new_lst

def startrec(I: List[int]) -> List[int]:
    return rec(I[:])