How do I concatenate two lists in Python?

Question

How do I concatenate two lists in Python?

Example:

listone = [1, 2, 3]
listtwo = [4, 5, 6]

Expected outcome:

>&g         


        

Answer 1

If you need to merge two ordered lists with complicated sorting rules, you might have to roll it yourself like in the following code (using a simple sorting rule for readability :-) ).

list1 = [1,2,5]
list2 = [2,3,4]
newlist = []

while list1 and list2:
    if list1[0] == list2[0]:
        newlist.append(list1.pop(0))
        list2.pop(0)
    elif list1[0] < list2[0]:
        newlist.append(list1.pop(0))
    else:
        newlist.append(list2.pop(0))

if list1:
    newlist.extend(list1)
if list2:
    newlist.extend(list2)

assert(newlist == [1, 2, 3, 4, 5])