Modify List In-Place

Question

I want to modify the list within a function, that will be later reflected onto the outer world so that it will change whenever we call a function. Yet, the list is unmodified.

def modify_in_place(a_list, start, end):
       a_list= a_list[start:end:1]
list_A=[1,2,3,4]
modify_in_place(list_A,1,3)
print(list_A)

list_A should return [2,3] but it returns [1,2,3,4]

Answer 1

You can assign to the full slice of the list to modify it in-place.

def modify_in_place(a_list, start, end):
       a_list[:] = a_list[start:end:1]