Convert your lists to sets first, then you can just do `set_unfinished = set_raw - set_finish`

`set` is the standard answer. However, if your lists are sorted, there are more efficient algorithms. One example of them is to traverse both arrays at the same time.

    List_finish = [1,2]
    List_Raw =[1,2,3,4,5]
    List_unfinished = []
    
    
    for raw in List_Raw:
        if raw not in List_finish:
            List_unfinished.append(raw)

I want to get a List\_unfinished  with \[3,4,5\] .

The above for loop is very slow in large list. Any efficient method ?

What is the efficient way to find the non duplicate items in two list ?