Compare and replace lists in function of their lenghts

I have Two lists, let’s say A & B :
(A is the reference name and B is the new name)

What I want is :
if A is bigger than B (len(A)=5 ; len(B) = 3) :the 3 elements B replace the 3 (=>len(B)) firsts elements of A (and print a warning message)

if B is bigger than A (len(A)=5 ; len(B) = 6) : the 5 firsts elements of B replace the 5 (=>len(A)) firsts elements of A (and print a different warning message)

if A= B then B replace A

I have a solution but I want to know if it is the fastest or the smartest way of doing it and if some functions do this kind of replacement automatically ?

A = ["A","B","C","D","E"]
B = [1,2,3,4,5,6]

if len(A)>len(B) :
    A[:len(B)] = B
    print("warning message")
if len(B)>len(A) : 
    A[:len(A)] = B[:len(A)]
    print("different warning message")

if len(A) == len(B) :
    A=B

Edit: correction of errors

>Solution :

Why don’t you do a slicing based on the minimum length of the two lists:

A[:min(len(A),len(B))] = B[:min(len(A),len(B))]

A=[1,2,3,4] and B=['a','b','c'] => A = ['a', 'b', 'c', 4]

A=[1,2,3,4] and B=['a','b','c','d','e','f'] => A = ['a', 'b', 'c', 'd']

A=[1,2,3,4] and B=['a','b','c','d'] => A = ['a', 'b', 'c', 'd']