You could try something like this:

list1 = [1, 2, 3, 4,5, 6, 7, 8, 9, 10]
list2 = []
i=0

while i !=len(list1):
    variabl = str(list1[i]) + str(list1[i+1])
    list2.append(int(variabl))
    i = i+2

Output:

[12, 34, 56, 78, 910]